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====== XLXR - On Suspension ======
(supplied by bgavin)

The first 7 pages of suspension from XLXR 
________________________________________
I decided to write up a thread on basic suspension set up because I seem to be answering the same questions over and over. I had to split up the paper into two different threads. The first starts below.

Here is an index of the different sections on both threads:

First 7 pages: 
Tire pressure
Shock preload
Rider sag and preload of forks and shock
Fork stiction
Chassis pitch
Shock spring rates 
How to select shocks 
My impressions of different shocks

Second 7 pages:
Fork spring rates
Works Dual Rate fork springs
Lowering a bike
Ricor Intiminators vs Race Tech Emulators
Fork oil viscosity, oil height, changing fork oil
Air Forks
Loosening drive belt and aligning rear tire
Deciding how to set up your bike
Wobble thread link and summary
More links to suspension threads

link to the second set of 7 pages on suspension
http://xlforum.net/forums/showthread.php?threadid=552796

I will start with the simple things and work into the more complex. If I mention something you don’t recognize, it is probably explained in more detail at a later point. Naturally, you can google any terms for more information. Wikepedia and the websites of the shock companies and Sport Rider have lots of good information. The information is based on experience with my 2006 Roadster. I weigh 260 lbs... Reading and learning about suspension is only the start. The only way to really learn about suspension is getting in the garage, make changes and test ride. In a year or two, you will be ready to buy a new bike and start all over. It is very common to think you know what the problem is. But you will never know for sure until you make the correct changes and the problem goes away.

If you want to work on your bike, you are going to have to buy tools. A bike jack, Torx bits, fork cap socket and clamp to get the forks caps back on is just a start. Whenever I jack up my bike, I use a motorcycle tie down strap from the handle bars up to a hook in the roof rafters to prevent knocking the bike off the jack. Be sure to read the other sticky links in the suspension section.

**TIRE PRESSURE**

The very first step is to check tire pressure. My 2006 owner’s manual says 30 psi front, 36 rear and increase the rear to 40 psi for two up riding. However, everyone has a different opinion. I found the stock front tire was so bad I had to run 40 psi in it to keep it from wandering from side to side down the highway. In addition, at 30 psi I could feel the rim bottom out against square edge bumps in big pot holes or driveway transitions. At the opposite end, too much air steepens the curve of the tire resulting in a smaller contact patch in the center, and that can reduce braking effectiveness. 

Another misconception about tire pressure is what the label on the side of the tire means. Those are maximum tire pressure recommendations when carrying the maximum weight capacity of the tire. If you are not at the maximum weight capacity, you do not need to run maximum tire pressure. 

With my Avon Venum X tires I run 35 psi front, 33 rear, solo. I found these pressures to make my bike handle best overall. Don’t simply use my pressures, do your own testing and find what works best for your bike.

**SHOCK PRELOAD**

Setting the shock preload is the next adjustment to work with. The preload adjuster is the collar under the spring that has different notches in it. Turning the collar upward with the special spanner wrench shortens the spring and that makes it stiffer Turning the collar downward lengthens the spring to make it feel softer. 

In theory, the standard springs are for a 185 lb.... rider. If you weigh more than 185 lbs..., you need to increase preload to stiffen the spring. If you weigh less than 185 lbs..., you need to decrease preload to make the spring softer. If you add a passenger, you will probably need to move the adjuster collar to make the spring as stiff as possible.

If the ride feels harsh and does not use all the shock travel, reduce preload. If the ride feels soft and bottoms out too much, increase preload. Some shocks may have a threaded adjuster, or have the adjuster on top of the shock.

“Bottoming out” happens when the spring is too weak for the rider’s weight and the shock compresses through all the suspension travel when hitting big bumps in the road. If you have the preload adjuster set to max stiff, and you still bottom out, you need a stiffer spring. 

“Topping out” is opposite of bottoming out. Topping out is when the shock fully extends and hits metal to metal when the bike is thrown up into the air over bumps. Topping out can feel as rough as bottoming out. Topping out can be caused by too little rider sag due to too much spring preload and/or too little rebound dampening.


In general, you want the shock to bottom out softly when you hit the biggest bump you ever hit. That way, you know you are using all the shock travel you available. You never want to bottom out so hard you break something or hurt your back. 

A plastic tie around the forks or shocks can be an important suspension tool. If you put a plastic tie on a fork or shock, and then observe different kinds of bumps, you can learn a lot about how your suspension reacts to different road conditions. For bikes with gaiters on the forks, you will have to figure out a way to hold them up in order to use a plastic tie on the fork.

**RIDER SAG AND PRELOAD of FORKS AND SHOCKS**

Setting rider sag in the forks and shocks is one of the first things you must do for proper suspension tuning. Rider sag of the shock is generally measured vertically, from the axle straight up to the fender. Rider sag of the forks is generally measured parallel to the forks, not vertically as with the shocks.

If you jack the bike up so the tires are in the air, the suspension is fully extended. As you lower the bike and put weight on the suspension, the suspension compresses a bit. That is called bike sag. If you then sit on the bike, the suspension compresses even more. That is called rider sag. 

Rider sag is the distance the forks or shocks compress when the rider is sitting on the bike. Generally you want the forks and shocks to compress 1/3 to 1/4 total travel when you sit on the bike. Nightsters and Lows with short travel suspensions, need to have rider sag set at the minimum in order to maximize usable travel. Roadsters can usually get away with a little extra rider sag because they have more suspension travel.

Changing spring preload changes rider sag. More preload stiffens the spring and reduces rider sag, less preload softens the spring and increases rider sag. Shock rider sag is set by turning the adjuster. Fork rider sag is set by changing the length of the preload spacer inside the forks. 

The absolute minimum fork preload you can use is whatever length is needed to take up the space between the top of the spring and bottom of the fork cap when the fork cap is screwed all the way down and the forks are fully extended. This will keep the spring from bouncing around inside the forks.

Another consideration is after 15,000 miles or so, the springs may lose a bit of tension, which is normal. If that happens, you may have to increase the length of the preload spacer a bit to compensate and get back to the original sag you wanted. Eventually, the springs may get so weak, no amount of preload will help. Then you have to get new springs.

The second thread has more details of fork set up.


**FORK STICTION**

Fork stiction is when the drag of the internal bushings is so high, checking rider sag becomes difficult because the forks compress to a different point every time you try to check rider sag. This is especially true for new forks.

Sometimes you have to push down on the forks and let them extend very slowly and measure that point. Then lift up on the forks and let them compress very slowly. In both cases, end up with your weight on the bike. Then use the difference between those two points as your rider sag. 

**CHASSIS PITCH**

Chassis pitch is the relationship of the front ride height (fork rider sag) to the rear ride height (shock rider sag). Usually, lowering the front end or raising the rear end, makes the bike turn sharper, but may make the bike unstable at higher speeds. Raising the front end or lowering the rear end usually makes the bike more stable at highway speeds, but reduces its ability to handle sharp turns. 

However, I found this did not apply to my Roadster. I found that setting up the chassis of my Roadster to be as stable as possible actually improved stability and confidence while cornering. 

The easiest way to check for the correct balance between front and rear ride height is to sit on the bike and measure if the frame rails under the engine are parallel to the floor. The front can be a bit higher (rear lower), but every time the front got too low (rear higher), my bike started to get a high speed wobble. Use the frame rails parallel to the floor as a starting point. I have verified this on my Roadster, XL 50, and Nightster, but not on Customs, Lows or XR’s. It may not apply to other bikes at all.

You must set rider sag of forks and shocks correctly before you set chassis pitch. Then move the forks up or down in the triple clamps to get the frame rails level to the floor with rider on the bike. Once you get a few test rides in, you can set the fork height to get the handling you prefer. 

Be very careful on the first test ride after making suspension adjustments. You could have set the bike up to wobble, even if it did not wobble before. On your first test ride, start off slowly, say 40 mph and give one side of the handle bar a little bump. If it wobbles, go home and fix it. If it doesn’t wobble, do 45 and give the bars an easy bump. Keep increasing speed in 5 mph increments until you can go as fast as you want without any signs of wobble. It is far better to find out you have a wobble at low speeds than high speeds. This I know from experience.

There is a link to the famous wobble thread and a summary of things that can cause a wobble at the end of the second 7 pages thread.

I like to set my forks in the triple clamps so the bike is very neutral around the average corner at average speeds. Once leaned over in a smooth corner, I can let go of the bars and the bike will just stay there. (I can’t totally let go of the bars because I have to keep the throttle steady.) 

If you are leaned over in the “average” corner and feel like your bike is turning in too sharply, raise the triple clamps. If you feel like your bike is trying to straighten out, lower the triple clamps.

I make no mention of shock motion ratio or fork rake and trail. If you want to change those beyond stock parameters, you are replacing major components or cutting and welding frames.

**SHOCK SPRING RATE**

Spring rate refers to how much force is needed to compress the spring a certain distance. Straight rate springs will compress the same distance under the addition of the same force at the beginning of travel as at the end of their travel. Progressive rate springs have a soft rate in the initial part of the travel, and transition to a hard rate in the final part of travel. If the rates are correct, this will provide a smooth ride over small bumps, yet resist bottoming out over big bumps.

For example, take a 4” long straight rate spring with a rating of 100 lbs.../in. The first 100 lbs... will compress the spring 1”, the second 100 lbs... (200 lbs.. total) will compress the spring 2”. It will take 400 lbs.. total to compress the spring all 4”.

A progressive rate spring is normally described as 75/125 lbs../in. The 75 lbs../in is the soft initial rate, the 125 lbs../in is the hard final rate.

Using a 4” spring rated at 75/120 lbs../in as an example, let’s assume it is wound to stay in the initial rate for the first 3” of travel. That means it will compress one additional inch for each addition of 75 lbs.. for the first three inches. Therefore, 225 lbs.. (75 +75 + 75) will compress the spring 3”. Then add 125 lbs.. to compress the last inch and you have 225 +125 = 350 lbs.. total to compress the spring all 4”.

However, the spring may be wound to have only 1” travel at 75 lbs../in and then the final 3” will be at 125 lbs../in. In this case, it will take 75 lbs.. + 125lbs + 125 lbs.. = 325 lbs.. to compress the spring 3”. Then add an additional 125 lbs.. to compress the spring the final inch. The total becomes 325 lbs.. + 125 lbs.. = 450 lbs.. total to compress the spring all 4”.

This designation of a progressive spring rate does not tell you anything about the where, or how quickly, the spring transitions from the initial to final spring rate. A progressive rate spring with the correct initial rate will provide a smooth ride over small bumps in the road. However, if the transition range is too short, or the final spring rate is too stiff, medium and larger size bumps will not compress the spring beyond the travel of the initial rate and the rider will feel a very stiff ride over those medium and larger sized bumps. 


**HOW TO SELECT A SHOCK** 

Start by deciding how long a shock you want, how much weight you want to carry, and how much money you want to spend. Shorter shocks and heavier riders need heavier springs. 

On Rubbermounts, shocks approaching 14 1/2" long may cause the lower run of the drive belt to drag on the linkage from the rear brake pedal near the master cylinder.

When you take the stock shocks off for the first time, hold the Torx bit still and loosen the nut. This will help prevent stripping the Torx head. 

If the new shock bodies are much thicker than stock, you will need longer bolts and spacers to keep the shock body from hitting the belt guard.

Go to Progressive Suspension’s web site and see what shock is recommended for your bike. The standard spring rate for 12.5” and longer shocks is 75/120 lbs../in and is for riders in the 185 lb... range. The heavy duty spring rate for 12.5” and longer shocks is 90/130 lbs../in, and is for 260 lb... riders and up. Whittlebeast found the springs for the longer shocks are actually “step” springs, meaning the transition zone between the initial and final rate is very abrupt. That provides a harsh ride over smaller bumps, but may resist bottoming better.

12” and shorter shocks use a 90/130 spring as standard, 115/155 as heavy duty. There have been plenty of riders who report shorter shocks provide a good ride. I suspect the big reason is the transition zone between initial and final rate is much longer and more travel is used over small to medium sized bumps. But shorter shocks will likely bottom out over larger bumps.

Check the specs carefully. Just because the overall length of a shock is longer, does not mean it has more travel. Note the spring numbers, springs with the same spring rate may have different part numbers to indicate other parameters such as diameter or length. Expensive shocks are not always better, especially if the spring does not match rider weight. 

**MY IMPRESSIONS OF DIFFERENT SHOCKS**

Stock shocks on my 06 Roadster were really bad. In order to keep them from bottoming out, I had to crank up the preload. Then they rode too stiff to be comfortable, and still bottomed out. Harley changed the spring rates in 09. I haven’t tried any 09 shocks, but they seem to be a great improvement because a lot less guys are complaining about the newer shocks.

The FXDX shocks on my Roadster were a good example how excessively short transition zone and excessively stiff final spring rate result in handling problems. I weigh 260 lbs.., the initial rate of the FXDX springs matched my weight pretty good and absorbed small bumps very well. However, the transition to the final rate was so abrupt, and the final spring rate was so stiff, it felt very harsh over medium size and larger bumps. This became a serious problem when hitting a series of medium sized bumps while leaned over in a corner. There was enough weight on the spring to compress it through the initial part of the spring just fine. However, there wasn’t enough weight to compress it into the final rate and the back tire would skip over the bumps and lose contact with the road. With the FXDX shocks, I was using only the initial part of the travel, and rarely got it into the final part of the travel. I have no idea if there are different FXDX shocks from different years with different springs.

The Whittlebeast Hybrid shocks, a Roadster shock body with a Custom spring (and spacers) were the opposite. The initial rate was pretty good, and the transition range was fairly long. Therefore, small and medium sized bumps were absorbed and provided a smooth ride. 

Whittlebeasts low stops and handles like a real sport bike
http://xlforum.net/forums/showthread.php?t=93767

Be sure to understand the part of putting the spacers under the springs to keep them from rubbing on the shock body.

The WB Hybrids prove cheap shocks with the proper spring rate and dampening curves are far better than expensive shocks with improper spring rates and bad dampening curves. Unfortunately, I was just a bit too heavy for the springs and they would bottom out every now and then. 220 lbs.. is about the max solo rider weight that both the WB Hybrids, and the standard 75/120 spring used on Progressive’s 12.5” and longer shocks, can handle without problems. 

Here’s an example illustrating how 30 lbs.. can make the difference between a particular spring riding smoothly or harshly. Doxbike weighs 230 lbs.. and tried Progressive 13.5” 418’s with the heavy duty 90/130 springs on his Roadster. The 418’s were always too stiff for him over small to medium sized bumps, but he kept trying to find the best compromise of rebound dampening and spring preload. I rode it, and felt it was pretty good, but I weighed 30 extra pounds. He rode my bike with the Whittlebeast Hybrids which provided a much softer ride without bottoming. However, with my 260 lbs.., bottoming the WB Hybrids was fairly frequent. He switched to Whittlebeast Hybrids and sold the 418’s. 

Based on this experience, I think for the 12.5” and longer shocks, the heavy 90/130 spring works best for riders 260 lbs.. and up. This leaves riders between 220 to 260 lbs.. without a good spring choice from Progressive Suspension. 

The 13 ½” long 1200S shocks are getting harder to find because they originally came on a frame mount Sportster for only a few years. They have a 54/78 lbs../in spring which is very good for 140 lb... riders on Rubbermount bikes. They also work very well for light weight riders on Nightsters when combined with a 1” lowering block so short legs can get their feet on the ground. They should work well with 180 lb... riders on Rubbermounts who do not ride two up. The 1200S shocks provided a very good ride for me on the highway because there was a lot of movement in the spring. However, I was too heavy for the spring and bottomed out too much.

There have been questions about riders, either solo or 2 up that weigh 300 lbs... The Road King air shocks are really the best option if you have a very wide range of weights to carry. They can be found on eBay for as little as $50. The parts guy at a local dealer gave me a pair for free, they were going to be thrown away. 


There are two basic lengths, the 11 ¾” and 12 ¾”. The longer ones are far more common and probably ride much better solo because they may have softer springs than the shorter shocks. They are generally too stiff for 150 lb... riders solo. But they work well enough for 180 lb... and up riders. They might be able to carry more weight than the Sportster is rated for. There are several part numbers for the RK air shocks, so it is difficult to be sure what differences there are. 

My Road King 12 ¾” shocks have 54565-97A, and another pair C on the end. The oil will drain out through the port for the air fitting if it is not capped off during shipping. The only way to tell how much oil is in them is to weigh them. Mine weighed 5 lbs.., 2 oz.. It is possible to change the oil in the shocks. I changed to 5w in attempt to soften them up, it helped a bit, but not enough to say it is worth the work. 

If you add oil, you must be very careful to not overfill the shocks. That could cause a hydro lock and blow them apart. Not something I have seen, only heard about. At the very least, you should put only one shock at a time on the bike with the air fitting removed, pump it several times to bleed all the air out, and then bottom it out so it will blow out all the excessive oil. Even then this is way too much oil because you will not have an air chamber on top of the oil level.

More discussion of RK air shocks with pictures of air shocks cut apart
http://xlforum.net/forums/showthread.php?t=273913

An easy way to change RK shock oil
http://xlforum.net/forums/showthread.php?t=269898

I am currently using 13.5” WP 3 Way shocks. WP is the European company, not Works Performance. 3 Way refers to having adjustable high and low speed compression dampening and rebound dampening. I had to send them back twice to get the dampening curves changed to work well. Even then, they sat on the shelf for over a year because I liked the WB Hybrids better. My 260 lbs.. ended up being too heavy for the 97/142 lbs../in spring, too light for the 154/228 lb.../in spring. 

Then the Ricor Intiminators came along for the forks. The Intiminators softened up the 154/228 lb.../in springs enough to ride smoothly enough over small to medium size bumps to be comfortable riding all day. These high end shocks really start to work well when pushing the limits of high speeds and rough roads. Far better than any other shock I have tried.

Harley 2 up shocks for a Nightster
http://xlforum.net/forums/showthread.php?t=509806

I haven’t tried these, but rider reports seem good.

The very first pair of shocks I bought were Progressive 440’s. They were hydro-locking and felt like a hard tail. This was before I figured out about loosening the drive belt. Maybe that was the problem. I have read one other report where an over tightened drive belt caused the 440’s to ride strange, and loosening the belt let them work better.

I also tried the Works Performance Pro Racers. I sent them back 2 or 3 times. They had a hard hit in them and Works only moved the hit deeper into the shock travel. I gave up on them.

The Progressive 440’s, Works Pro Racers, and the WP 3 way shocks I have now, all have some type of check ball and spring valving system. None of them worked very well. It seems the check spring and ball system was just never tuned correctly to match my weight and bike. 

The best shock I have ever ridden on was a Penske 3 Way shock on a Ducati Monster. I try hard not to laugh when someone says how good Progressive 412’s are.


----------------------------------------
Link to the second set of 7 pages on suspension
http://xlforum.net/forums/showthread.php?threadid=552796
I had to split up the paper into two different threads.
----------------------------------------
Former Ricor test rider for IAS Shocks, Intiminators and Vibranators. Works Dual Rate fork springs, fork brace, Avon Venom X tires, loosen drive belt, and set frame rails level to floor. Read the "7 Pages of Suspension" thread in the Suspension Sticky Index to learn how to fix your suspension. 
----------------------------------------
Last edited by XLXR; 17th July 2009 at 23:50 


The second 7 pages of suspension from XLXR 

**FORK SPRING RATES**

Here are some numbers I have collected over the last 2 years. I have forgotten how I got some of them. Some I measured in my garage, so they are estimates. The Works Dual Rate Spring numbers are accurate because they came directly from Works.

Stock fork spring on 06 Roadster:
20 lbs../in initial rate, 40 lbs../in mid-range, 90 lbs../in final rate. I thought the stock fork springs felt way too soft. I think the reason is the spring should be in a fork with 8” of travel. With only 4 ½ travel in the Roadster forks, the springs never had enough travel to transition to the harder spring rates in the mid-range and end range. 

Stock Low, I think from an 06 bike:
25 / 40 / 70 lbs../in. If this number is correct, it is probably designed for lighter riders than the Roadster spring.

Stock 07 Nightster:
25 lbs../in. This is a number I found written in my notes from working on Road Chick’s Nightster. I don’t know if the final rates get stiffer, but I do know it was way too light as set up with stock preload. Even too light for 140 lb... riders.

Progressive Suspension’s 11-1527 fork spring:
35/50 lbs../in. This spring is designed for the longer forks. I think it is too long for the Nightster and Low forks because they do not have enough travel to transition to the harder final rate to prevent bottoming. Unless you are a very light rider and need a softer ride.
In these first 3 cases, adding preload will stiffen the spring. But the question becomes if you can physically get enough preload in the forks to stiffen up the springs enough to prevent bottoming.

Race Tech has 4 straight rate springs:
45, 47.8, 50.6, and 53.4 lbs../ in. I tried the Race Tech emulator and 53.4 lbs../in spring. I found their recommendation to be way too stiff. I will explain in more detail when I compare the Race Tech emulator with the Ricor Intiminator.

Works Dual Rate fork springs:
This is the most flexible spring made for Rubbermount XL’s. It can work in the long suspension of a Roadster and short suspension of a Nightster simply by changing the length of the crossover spacer. By test riding with different crossover spacer lengths, I learned more about how spring rate effects handling than anything else I have done.

A picture of The Works Dual Rate Fork Spring kit. Click on the Dual Rate Fork Spring Kit link on the left.
http://www.worksperformance.com/html/street.html

Sportytrace's thread on her 08 1200 Nightster with Ricor Intiminators and Works Dual Rate fork spring kit.
http://xlforum.net/forums/showthread.php?t=446320

This link has pictures of how to remove and replace fork springs, comparing stock fork spring with the Works, and showing how the crossover spacer fits in the shorter spring. You can see how the coils are wound differently at either ends of the stock spring to help you understand how reversing the spring can change oil level because more or less coils are under the oil level. It also describes how she is fine tuning the forks and suspension. It also has cbnightster's description of putting Low damper tubes in the Nightster forks to gain 3/4" travel, which is huge.

Works gives you 3 crossover spacers of different lengths which fit inside the shorter spring. I test rode with different spacer lengths until I found I liked a 2 1/4" length best for my Roadster. Works say you can use different length spacers in either fork to get a triple rate spring effect. But I didn't find that necessary.

The kit is composed of two separate springs. The soft version of the kit has a short spring with an 80 lb.../in spring rate and a long spring with a 60 lb.../in spring rate. The springs are stacked on top of each other. The soft initial spring rate, which is also called the “total” spring rate, results when both springs are compressing at the same time.. Here is the mathematical formula:

1/total spring rate = 1/short spring rate + 1/ long spring rate.

34 lbs../in. = 80 lbs../in (combined with) 60 lbs../in

The short spring has a metal tube in it which is called the crossover spacer. The length of the tube will limit how far the short spring can compress as the forks go over bumps in the road. When the short spring bottoms out against the crossover spacer, only the long spring continues to compress from that point. That provides the hard final spring rate of 60 lbs../in. 

Here is the bottom line. Nightsters need a crossover spacer between 4 1/4" long and 4 ¾” long to get the spring to transition very early in the fork travel. SportyTrace is still working on finding the optimum crossover spacer length for her Nightster, she will let us know what she finds. It seems adding the Ricor Intiminators have made readjustment of the forks necessary. The link to her thread is a few paragraphs below.

I like a crossover spacer about 2 ¼” long for my Roadster. That will put the transition point much lower in the fork travel. You are going to have to do some test rides to find which crossover spacer length works for you because the amount of preload/rider sag in the springs will move the transition point lower in the fork travel, and I have no idea how to calculate that correctly. 

The final aspect to understand about the Works Dual Rate kit is that the two individual springs will compress different distances under a specific weight. I got myself so confused about this I had to ask Folkie for some help. The following chart does not take into account the rider sag moving the transition point lower in the fork travel, so it is more for general understanding. Here is his explanation:

Travel of the 80 lb.../in spring is 75% of the travel of the 60 lb.../in spring.

For any amount of total travel (at the crossover point), 3/7 of the total will be the travel of the 80 lb.../in spring, and 4/7 of the total will be the travel of the 60 lb.../in spring. This is because 3/7 (of something) is 75% of 4/7 of the same thing.

(Total fork travel 
At crossover) = 80 lb... spring travel + 60 lb... spring travel

1" = 0.43" + 0.57"
2" = 0.86" + 1.14"
3" = 1.29" + 1.71"
4" = 1.71" + 2.29"
5" = 2.14" + 2.86"
6" = 2.57" + 3.43"
7" = 3.00" + 4.00"

The 80 lb... spring with the cross over spacer in it is 5” long. If you want the crossover point to be at 1” total fork travel, you subtract the .43” in the chart above from 5” of spring length.

5” - .43” = 4.57” which is the length of the crossover spacer needed to get the forks to transition at 1” total fork travel. This is in the area needed for Nightsters.

For Roadsters, 5” – 1.29” = 3.71” which is the crossover spacer length close to what’s needed to get the forks to transition at 3” total fork travel. 

I have a 2 1/4” crossover spacer, my 80 lb.../in spring has a travel of 2¾", then the 60 lb.../in spring has a travel of 2¾" × 4 ÷ 3, = 3.667". 2¾" is 75% of 3.67".
So when the heavier spring hits the transition point, total travel is 2¾" + 3.67", = 6.42". But my Roadster forks don’t have 6.42” of travel. The preload on the spring and rider sag, is probably creating the error between the actual transition point and the calculated transition point.

It seems the biggest mistakes people make when setting up their forks is not understanding the correct things to measure and change. Put a plastic tie on the forks to see how much travel you are using by test riding over the biggest bumps you hit or by doing a hard stoppie. Measure the fork rider sag to see how much you have to start with. Measure chassis pitch and how far the forks stick above the triple clamp. When you take the springs out, measure the fork oil level, and total travel of the forks. Write down all your measurements.

Just because you have the same length of spring or preload spacer sticking out of the forks before you put the caps back on, does not mean you will have the same rider sag as your buddy, (although it should be close). You must check your own rider sag.

Do not assume the fork oil height is correct. Measure it. Make sure you pump the forks enough to get all the oil out before refilling it. Make sure you pump the forks again after you refill it to bleed out all the air. Recheck how much fork travel you are using by test riding. If you are not using all available travel, you may have too much oil in it. If you suck out 1/4 to 1/2 oz. oil, and you gain travel, you had too much oil in it.


**LOWERING A BIKE**

People like the Tamarack lowering blocks
http://www.tamarackmw.com/

Link to Progressive web site with picture of lowering springs and damper rods
http://www.progressivesuspension.com/pdfs/updates/3055-110HarleyForkLowerKit.pdf

Page 28 of Progressive catalog has color pictures of Drop In Lowering Springs in cut away forks
http://www.progressivesuspension.com/pdfs/PSI2009Catalog.pdf

A link discussing Progressive's Drop In Fork Spring kit 
http://xlforum.net/forums/showthread.php?t=433127

Some people need to lower the bike to be able to get their feet on the ground. Others want to lower their bike to attain a certain look. Either way, lowering the bike causes 2 problems. First problem is the reduced cornering clearance. The second is limiting total travel. With limited travel, it becomes very important to set up all other aspects of suspension tuning correctly because there is little room for error.

Lowered bikes can be dangerous, especially if the rider pushes the limits of cornering or speeds. I read one report where a guy’s kick stand caught on a manhole cover and threw him off the bike. 
Last year, I was following a $30,000 custom bike with lowered suspension. The guy was getting throw off the seat just going over normal size bumps. He hit a big bump while in a curve, almost lost control and almost ran off the road. This was at only 45 mph. 


In order to get lowered suspensions to work, you must use stiffer shock springs. Stiffer springs provide a stiffer ride. Carrying a lot of weight, such as 2 up riding, generally means using a shock spring that is so stiff, solo comfort is severely compromised. Or, if you get a spring soft enough for a solo rider, it will probably bottom out too much when 2 up.

However, IF the spring has long transition zone, IF the initial and final spring rates match rider weight, and IF the rider goes slow enough and IF he avoids major bumpy roads, it is possible to get a reasonable ride. I guess I should add another IF. IF the rider has no clue what good suspension really is, anything is better than stock.

Sportytrace is a 140 lb... rider who needed to keep her Nightster low so she could keep her feet on the ground. We accomplished this by using the 13.5” 1200 S shocks which have a light 54/78 lb.../in spring. The spring matched her weight, but in order to get her feet to the ground, we had to use 1” lowering blocks. This proved a very good combination for her. 

Sportytrace’s Nightster set up with Intiminators and lowered 1200S shocks.
http://xlforum.net/forums/showthread.php?t=164018

Combining the 12¾” Road King air shocks with the 1” lower block is another good combination to carry a lot of weight while keeping the bike low. Be careful to not exceed the factory weight limitations of the bike itself.

There have been questions about how using lowering blocks affect the spring rate. The answer is it all depends on too many factors to predict accurately. I experimented with 1” lowering blocks. Some shocks smoothed out a little bit, others didn’t.

When you lower a bike, you must verify you have enough tire clearance. If you jack the bike up and take off both shocks, and then lower it very carefully, you can see how low it can go. Measure the shortest distance between the shock mounting bolts. The shocks bottom out and that limits how low the rear of the bike can go. If you take off one shock and lower the bike to bottom out the shock, you can verify you have enough clearance left over. 

Early years of Rubbermounts had electrical wiring under the rear fender that the tire can rub on.

Nightsters have a reflector under the fender that will hit the belt guard. Early shocks from Progressive had too much travel and broke off the reflector. The newer shocks have less travel. So be careful if you buy older shocks for a Nightster.

If you lower the front end by lowering the triple clamps, it is possible the lower fork tubes will hit the lower triple clamp when the forks compress fully. The first 07 FI bikes had front fenders that hit the voltage regulator. Something you want to avoid.

Lowering, or raising, a bike may make it necessary for a kick stand of a different length.
There are 3 lowering kits for forks that I am aware of. Harley offers their own kit with a new spring and damper tube. This kit is not very common. I suppose because it is too expensive, especially if you have to pay the dealer to do the work.

Progressive offers 2 different lowering kits. The original 10-1560 kit uses the standard 11-1527 main spring, but includes extra 1’ springs called lowering springs. Harley calls them rebound springs. Others call them top out springs. These springs ride on the damper tube in between the upper and lower fork tube. Stock forks have only one rebound spring which softens the hit when the forks fully extend and the fork tubes hit against each other. Adding 1 or 2 extra lowering/rebound/top out springs pulls the upper fork tube farther down into the lower fork tube. The big disadvantage is you have to take the damper rod out to add the extra springs.

Progressive’s new kit is 10-200 “Drop In” kit. In this kit, the main fork spring is replaced with 2 different springs. You do not need to remove the damper tube to do this, just pull out the original spring and drop in the new springs. The long spring is the main spring which supports the bike’s weight and compresses and extends in response to road bumps. The other spring is very short and weak. It is so weak, just the weight of the bike will cause it to compress 2” until the coils hit each other. This is called coil binding. When the coils hit each other, the weak spring stops compressing and becomes a solid rod, leaving the other spring to do all the work. You can see pictures on Progressive’s web site.

I have no experience with either lowering kit. Neither offers the adjustability of the Works Dual Rate spring kit.

**RICOR INTIMINATORS vs RACE TECH EMULATORS**

Both are valve bodies which you install between the damper rod and fork spring. Both control oil flow and compression damping, but in dramatically different ways with dramatically different effects on the ride and handling of the bike. 

To give you better idea how forks provide damping, there is a picture of stock damper rods from a Nightster and a Low a few paragraphs below, post 289 of the Intiminator thread. The large holes to the right are the compression damping holes. As the forks compress, oil is forced through the compression holes. The holes resist the oil flow and that provides compression damping. Drill the holes larger, more oil flows and less resistance is created, and the forks can compress faster in response to road bumps.

The rebound damping holes are on the opposite end of the damper rod. Rebound damping is created only when the forks extend and forces oil through those holes. 

The Emulators have a valve stack which control only compression damping. A valve stack is like a bunch of washers stacked on top of each other. When the forks compress, the oil pushes on the washers, bending them open and the oil flows through. A threaded rod with a spring and nut goes through the center of the washers. If you tighten the nut, the spring puts more pressure on the washers, reducing how much the washers can bend, increasing compression damping, and making the forks feel stiffer. 
This is basically the same way cartridge forks work. However, good forks have one shim stack for compression damping, and another for rebound damping. Similar to damper rods having compression holes at one end, and rebound holes at the other end.

Race Tech’s recommendation for me was to use their 53.4 lb.../in (95 kg/mm) straight rate spring, drill out the compression damping holes in the damper tube and use 20w fork oil. Trying to force 20w fork oil through the rebound holes created way too much rebound damping. 

I started to reduce the Emulator spring tension to reduce compression damping. I eventually got to the point where I took the Emulator out completely. Then I reduced fork oil viscosity from 20 to 10 to 5w. 5w provided too little damping. 10w was good. 10 w oil with the compression damping holes drilled out, but the stock rebound holes, provided the best balance. Or so I thought until the Ricor Intiminators came out.

The Ricor Intiminator actually has 2 separate oil circuits. The first is controlled by a metal collar that floats on a spring. When the wheel is not moving up or down, the collar blocks off some oil ports. When the wheel moves up in response to a bump in the road, the collar’s position remains stationary but the ports move up with the wheel. When the ports are uncovered, massive amounts of oil can flow through. This effectively blows off (high speed) compression damping which allows the forks to compress very quickly and absorb bumps in the road.

The second circuit is a shim stack. It provides damping to keep the chassis from falling down as the wheel moves up. 

Another big difference is the Race Tech 20w fork oil recommendation drastically increases rebound damping, but the Ricor 5w fork oil recommendation reduces rebound damping. 

This is why I constantly say the stock forks are over damped. Changing to 15w fork oil in stock forks over damps already over damped forks. 

The main Intiminator thread
http://xlforum.net/forums/showthread.php?t=423091

Post 53 has an animation of how the Intiminator works. However, for our bikes, the oil ports are above the moving yellow collar. If you look at the tube in the very center of the animation, near the bottom where the collar reverses direction, you can see the ports open and close as the collar moves up and down

My test rides are on posts 136, 173, 185, 295.

Post 289 has pictures of fork damper rods.
Post 298 CBNightster explains how to change damper rods. He used a Low damper rod in his Nightster to get some extra travel.
Post 337 is a picture of my fork cap installation clamp.

Trying to compare Intiminators to Emulators is like trying to compare a Corvette to a Chevette.


**FORK OIL VISCOSITY, OIL HEIGHT, CHANGING OIL**

Fork oil viscosity controls how fast the forks can move up and down in response to road bumps. Fork shaft speed is the term used to describe how fast the forks can compress and rebound. The stock fork oil viscosity is 10w. 5w reduces damping so the shaft speed increases in response to road bumps. 20w increases damping which slows the shaft speed.

Going too far in either direction can be dangerous because the wheel may lose its ability to stay in contact with the ground. It is entirely possible you could ride many miles without a problem and then hit the wrong set of bumps at the wrong time.

I have a 100 mile suspension test route that I use for suspension testing. It includes everything I ever encounter. High speed, low speed, mountain roads, multi lane highways, big and little bumps, and even a few dirt roads thrown in. After I took out the Emulators and reduced to 5w fork oil, I found one, and only one, set of bumps that caused the front wheel to hop and lose contact with the road surface. I switched back to 10w and the problem was gone.

Doxbike tried Harley Screaming Eagle heavy duty fork oil. 20w. It slowed the fork shaft speed so much I could see light under his tires on concrete highways. He had the Progressive fork spring and stock damper rod holes. He tried 5w and also felt it was too under damped. He went back to 10w and the problem was gone. 

The only exception is to use 5w when you use the Ricor Intiminators.

Never assume oil height in your stock forks is what it is supposed to be. I have seen several Harley and non-Harley bikes with improper fork oil heights from the factory. It is always a good idea to take the springs out and measure fork oil height first whenever you start making changes to the forks. This will verify your starting point. 

Oil height can be changed by changing springs, or just by turning the springs upside down. Springs with progressive rates have one end with the coils very close to each other. Putting those coils under a set oil quantity can increase the oil height when compared to a spring with fewer coils under the oil level. I like to have the loosely wound coils down to allow for more oil for a given oil height.

Oil height controls bottoming of the forks. (Spring rate, preload, oil viscosity, and rider weight also have some effect on total fork travel.) There is an air chamber above the oil. As the forks compress, the air chamber compresses increasing air pressure, and that creates more resistance to any more fork compression. If you add way too much oil, the forks will lock up and not move at all because the liquid oil cannot compress. 

When you change the fork oil, you must pump the forks up and down to get out all the oil. Letting them just drain will end up with too much oil if you just add what the factory recommends. If you put a plastic bag around the bottom of the fork, it will catch the oil instead of squirting it 3 feet across the floor when you pump the forks. 

Be careful removing the small drain screws. They will strip very easily. It is a good idea to replace them with Allen head bolts.

The manual gives recommendations for oil quantity and how far down the oil level should be from the top of the forks. They state the oil level must be measured with the forks off the bike and held vertical, spring out and fully compressed. 

I never do it this way because I do not want to take the forks off the bike every time I change oil. And, I do not like to compress the forks when the bike is on the jack because that might knock the bike over.

Tilt a glass full of water and see how the distance from the oil level is different to the top of the glass on the low and high side. 

When I add or change oil, I pour in an extra ½ oz. It is very important to pump the forks to get all the air out before you measure oil height. Then I use a turkey baster with a hard copper tube to put down the forks and suck out any extra. I put a plastic tie on my copper tube to set the level I want. The first time I do this, I add the factory recommended amount of oil, pump the forks, measure the distance with springs out and forks fully extended. That establishes my base level which I compare all future adjustments to. I always measure down the back side of the fork tube. 

Generally, you can add up to 2 oz.’s extra oil for the long forks, 1 extra oz. for the short forks. It is very important to establish total fork travel and use a plastic tie on the forks to ensure you can use all available travel. Too much oil can hydro lock the forks and cause seals to blow out or maybe worse.


**AIR FORKS**

Adding air valves to the forks has a similar effect as adding oil to reduce bottoming. It is just another option. If you already have the tools, it is cheap and easy. Having to buy the tools makes it more expensive.

The fork caps are so thick, you can back drill the cap from underneath to reduce how many threads you have to cut. 

No one knows who much air pressure can cause damage. I doubt if anybody would ever need more than 5 psi. One big advantage of air forks is they are very easy to adjust for different riding conditions. Another advantage is it makes it easier to add or remove oil with a small tube.

Air fork mod tutorial
http://xlforum.net/forums/showthread.php?t=500980


**LOOSENING THE DRIVE BELT and ALIGNING REAR TIRE**

As delivered by my dealer, the drive belt was so tight on my Roadster it would jerk the engine backwards as I rode over bumps in the road. The belt is tightest when the rear axle is in line with a line formed by the swing arm bolts and the center of the front pulley. This is because the axle is rotating on a different radius and center than the drive belt. 

13.5” shocks on a Roadster move the swing arm through this point. Bikes with shorter shocks do not move though this point, however, the belt still gets tighter as it approaches full shock travel of the shorter shocks.

An over tightened belt will give the bike a very strange flexy frame feeling when you hit a big enough bump. Really scary in corners.

If you take the shocks off, move the rear tire up and down so the axle moves through the line formed by the swing arm pivot bolts and center of front pulley. You will feel the swing arm bind up if the belt is too tight. ½ turn on the adjuster will go from binding to not binding.

You must also align the rear tire. I use a piece of aluminum 1” angle. I put a small bolt on one end and ground down the tip of the bolt to fit in the dimple in the center of the swing arm pivot bolts. I locked the bolt in place on the aluminum angle with nuts and adjusted the length to clear the foot pegs. I used a plastic tie on the opposite end to set and compare the distance on both sides. 1/64” accuracy is probably good enough.

**DECIDING HOW TO SET UP YOUR BIKE**

If you want to get the opinions of other riders about particular suspension set ups or components, be sure to ask the right questions. Start off with rider weight, length of shocks, spring rates, preload settings, chassis pitch, how aggressive a rider is he, what type of bike he has and what kind of riding he does. Slower riders don’t need fork braces and better tires. If the guy’s weight is a lot different than yours, his opinion will not help you much. 

Getting RK air shocks and adding oil and preload to the forks is by far the cheapest suspension mods. Adding air valves to the forks is next.

Spending the money for Intiminators is a good place to start, especially if you think your shocks are a bit too stiff. With the Intiminators, you might be able to reduce shock preload enough to make the shocks you have comfortable.

If you really want to ride aggressively, you will have to add better tires, I like the Avon Venom X’s, fork brace, Intiminators with drilled out compression damping holes, Works Dual Rate springs and high end shocks. So far Ohlins are the only shock I have not heard any complaints about. However, Ricor is still working on their inertia shocks.

If anyone sees glaring errors, let me know in the next week so I can fix them.

More links to make you really crazy.


The famous Wobble thread
http://xlforum.net/forums/showthread.php?t=33294

Common causes of wobble are bad tires, loose spokes, loose nuts or bolts on suspension components, warped wheels, misaligned rear wheel. over tightened drive belt, loose steering head bearings, rider has too tight a grip on the bars, windshields, no fork brace, front too low or rear too high creating too much forward chassis pitch, improper tire air pressure. 

Did I miss any?

If you have the wire spoked wheels, you can tap the spokes with a small wrench. If they make a ring sound, they are tight, if they make a thud sound, they are loose. Tightening spokes improperly can warp the rim, if you don't know what you're doing, take it to somebody who does.

Rubbermount pivot shaft / wobble investigation with lots of pictures
http://xlforum.net/forums/showthread.php?t=473423

Harley data base of springs and shocks by Whittlebeast
http://xlforum.net/forums/showthread.php?t=47542

Fork info on an 883R with 144 lb... rider by Colinb
http://xlforum.net/forums/showthread.php?t=88966

An excellent series of suspension articles which I didn't write.
http://xlforum.net/forums/showthread.php?t=40821

And the original It ain't the Rubbermount and it don't have to ride stiff and handle lousy!!! for those who just can't get enough.
http://xlforum.net/forums/showthread.php?t=58815

-------------------------------------------
Former Ricor test rider for IAS Shocks, Intiminators and Vibranators. Works Dual Rate fork springs, fork brace, Avon Venom X tires, loosen drive belt, and set frame rails level to floor. Read the "7 Pages of Suspension" thread in the Suspension Sticky Index to learn how to fix your suspension. 
-------------------------------------------
Last edited by XLXR; 22nd July 2009 at 23:09 


Comments: (by who??)

Calculating or measuring rake and trail is not necessary unless you are making significant changes from stock chassis parts. I'm not saying they are not important, just that stock bikes have limits built into them.

Chassis pitch due to front and rear ride height changes is just easier to understand and measure. Measuring and setting the frame rails level to the floor with the rider on the bike is just a safe starting point for Roadsters. The most important thing to understand is if you get into a stability problem, at least raise the triple clamps to reduce forward chassis pitch, assuming there are no other related problems.

2007.02.18
From my experience with Race Tech emulator kit and straight rate fork springs, Progressive 440's and Works Pro Racers and dealing with the technical people, I know none have actually done testing with a Rubbermount Sportster, at least not when I purchased (and returned) the products I mention. I know Progressive is taking off the shelf shocks, putting on springs to match rider weight, but not changing the dampening curve to match the spring rate. I know Works has no idea how to make their Pro Racers work for me, I weigh 230 lbs..

Have you read the wobble thread, or at least the last 10 pages? Part of the problem is the Roadster has to have a very specific set up with front and rear ride heights and swing arm and frame positions, and loose belt tension, fork brace and better tires to handle properly for guys my weight. The aftermarket shock companies are giving us rider sag specs, spring rates, dampening curves, and shock lengths and travel that do not account for the unique needs of Roadsters. I mention Roadster because that is what I have.

Most Sportster riders just accept lousy riding qualities as a fact of life. Most do not understand how to improve upon junk and flat wrong set up information provided by HD and aftermarket companies. By trial and error, and ignoring what the "pros" recommend, I have improved the ride and handling of my bike way beyond stock. Not done yet, but getting close.

In order for this information to be meaningful enough for the guy who is just starting out, much more information is needed. Rider weight, riding skill level, front and rear rider sag, frame and swing arm position, tires, fork oil etc. etc. Because the correct spring rates will not help if too many other things are out of adjustment.

2007.03.03
I measured out XL 50's XL 50. Everything is stock:

Frame rails level with floor.
Swing arm is slightly above level. (Read the wobble thread page 53, post 526, and keep reading until you see the picture of the fat and happy rider.)
11 1/2 eye to eye shock length (fully extended) with 3/8" rider sag.
2 1/2" rider sag in the forks.

I won't repeat everything I have done to my suspension, but at this point I think XL 50 has the perfect set up on his bike. To me it illustrates you must consider how spring rate, length, preload, etc. of both forks and shocks affects frame and swing arm position with the rider on the bike. 

I also found that if the fork springs are too stiff for the rider, the back end feels too stiff, not the front end. I'm not entirely sure why, but something about "coupling." Instead of absorbing bumps, the stiff front forks transmit the force to the shocks and preloads the springs. More preload on the shock springs makes them ride stiffer.

My assumption is that the stock suspension is for the 180 lb.. rider. A 130 lb.. rider will find the bike rides too stiff. Putting a lighter spring on the shocks will help reduce ride harshness for the 130 lb.. rider. But now a 200 lb.. rider will find the shocks too soft. It may be necessary to put a progressive or dual rate spring in the forks (and/or shocks) to be able to decrease the initial spring rate, yet increase the final spring rate, to find a good compromise for both riders. 

Ideally, you would want to find the spring combination that allows the 130 lb.. rider to have a comfortable ride with no shock preload, and the 200 lb.. rider to be able crank in just enough shock preload to stiffen up the ride for him.

Increasing the oil level in the forks is one way to reduce braking dive for the heavier rider. The lighter rider probably won't be using full fork travel, and won't even notice.

Another way to build in some adjustment in the forks is to put a Schrader (air) valve in the fork caps. The lightweight rider may be good with no pressure, the heavy rider might want to add a few pounds of air pressure. I haven't done it, but it is an easy way to get some adjustability in the forks. I have had other bikes with air forks.

This is a very brief summary. Changing spring rates usually works best by changing the compression and rebound dampening curve also. As far as I know Roadsters and XL 50's share the same fork geometry. I don't know how much different the Customs and Lows with their raked front ends will be with these changes.

2007.09.18
Basically, preload is used to fine tune ride height (also called rider sag) to better match the weight of the rider to the movement of the spring. For example, if you are going to carry a passenger, tightening up the preload can keep the suspension from sagging too low and prevent bottoming out on the bigger bumps in the road. It is used to set the ride height (rider sag) of the suspension at 1/3 to 1/4 of the total suspension travel. It can be used to determine if the spring is too heavy or too light for the rider's weight. 

Preload in forks is set by the spacer length. The preload for shocks is set by rotating the preload adjuster.

All shocks and forks have a fixed amount of total travel. The travel is measured as the distance from full extension (topped out) to full compression (bottomed out). When you sit on the bike, you generally want the forks or shocks to compress about 1/3 to 1/4 of the full travel. You need this sag to allow for the suspension to travel both up and down from that point. 

The maximum travel of the shock body (or forks) may or may not be the same maximum travel the spring is capable of, and travel may also by limited by chassis design, i.e. tires rubbing. But we will ignore that point for now. 

What happens when a heavy rider sits on a shock with a spring that is too light? The spring cannot support his weight and compresses too much. Instead of rider sag at 1/3 travel, he may compress the spring to 3/4 of the available travel. Let’s say he weighs 300 lbs., but he has a 100 lb./in spring with 4 inches of total travel. When he sits on the shock with no preload, he compresses the shocks 3 inches and has only 1 inch of travel left over to absorb road bumps. Every bump in the road 1 inch and over in height makes the shock bottom out, very uncomfortable. Once the spring is fully compressed, it then rebounds (fully extends) with close to equal force. This is what throws a rider off the seat. Nightster riders are finding out how bad 1 inch of travel is. 

So he gets out the preload adjusting spanner wrench and starts cranking in more preload. By doing this, he is putting the spring under pressure. We can't measure the pressure, but we can measure the distance the spring is compressed. With no load on the spring it was originally 4 inches long. By adding preload, he has now compressed the spring to 3 1/2 inches. That 1/2 inch is the same as 50 lbs. of force on the spring. When he sits on the bike, it now compresses only 2 1/2 inches (rider sag)instead of the original 3. Still too much rider sag, he needs to get to only 1 inch rider sag, so he cranks in even more preload.

If he cranks in 1" of preload (100 lbs. of force on the spring), he gets 2" rider sag. Still too much sag.

If he cranks in 2" of preload (200 lbs. of force), he gets the 1" of rider sag he is looking for. 

But look what happened to the spring. While sitting on the bike, it has only 2" of travel left. (He wants to get the full 3" of travel beyond the 1" rider sag.) But that is only half of his problem. Since the spring is now preloaded with 200 lbs. of force, it now takes 201 lbs. of force to even get the spring to move and it will now take 300 lbs. of force to get the spring to move the first full inch. Unfortunately, it will only take another 100 lbs. of force to get the shock to bottom out. This is one lousy ride, as soon as he get the suspension moving, it is already bottoming out.

What he needs is a 300 lb. spring with 4" travel. With zero preload, he will get his 1" rider sag, and still have 3" travel left over to absorb road bumps.

Time out for Whittlebeast to edit and check my math and reasoning. If you guys are able to get through about another page of reading, you will be able to argue with any sales clerk about your suspension. Don't bother arguing with the engineers, they never let you win.

Now we will talk about progressive springs. A progressive spring is described with two spring rates, such as 75/120 lbs./inch. For our initial discussion, we will state the 75 lbs./in rate is the initial rate which controls the motion of the shock for the first 1 inch of travel. The 120 lb./in is the final rate which controls the motion of the shock for the last one inch of travel. The middle one inch of travel has a spring rate that progressively increases from 75 to 120 lbs./in. 

The main advantage is that progressive springs provide a softer ride over 1" bumps in the road, but quickly stiffens up to reduce bottoming over 3" bumps in the road. You get the best of both worlds, well not quite. The question becomes just exactly where is that transition point where the progressive spring crosses over from the soft / low initial rate to the hard / high final rate.


We will assume the 75/120 spring rate on a 13 " shock is for the 180 lb. rider. But if we put our 300 lb. rider on these shocks, he will blow through the compression stroke even faster because of the lighter initial rate. If you watch the spring coils compress as the overweight rider sits on them, you will see the coils in the soft part of the spring bind up (also called stack) against each other. He never even feels the soft initial rate. If we put a 120 lb. rider, she will feel an even stiffer ride because both the initial and final rate are too stiff for her.

Adding too much preload to a progressive spring can do the same thing the heavy rider does. It is possible for the preload to coil bind (stack) the initial part of the spring before the rider even sits on the bike. This is why it is critical to get the proper initial rate of a progressive spring, and then use only the minimum preload needed to achieve the correct rider sag.

Now let’s say Mr. Know Nothing About Suspension McKool wants that cool looking lowered look that a 11" shock provides. In just a few hundred miles he will realize that stock HD shock is really miserable. It is not uncommon for Harley suspension components to have the wrong spring rates and really bad damping curves. Harley tends to take the same shock body, shorten the shaft of the shock and then stick on whatever spring they have an excessive inventory of. A typical example is the 1" shock travel found on Nightsters. So he goes to the Progressive Suspension company website and finds the 11" 412-405B/C shock has 1.9" of travel, almost double the stock travel. But the spring is 90/130 lbs./in. A shorter shock must have a stiffer spring to compensate for the shorter travel. Problem here is that his initial rate has gone up from 75 to 90 lbs./in. That makes the ride even stiffer. This is the compromise riders with short travel suspensions must make.

When you buy a standard shock, changing preload is the only adjustment you can make. However, Works Performance sells what is called Dual Rate springs for forks and shocks. There are actually two separate springs, one stacked on top of the other. One spring has a soft rate, the other a hard rate. The initial spring rate is the combination of both springs compressing together. There is a metal tube inside the high rate spring which limits its travel. When the high rate spring is bottomed out against the metal tube, also called crossover spacer, the spring rate changes from the low initial rate where both spring were compressing, to the final rate which is now the softer spring compressing by itself. The big advantage with Works Dual Rate spring kit, is that you can change springs to give you the initial and final rate you want, as well as control the crossover point by changing the length of the crossover spacer. There is a formula to calculate the actual initial spring rate that results from both springs compressing together before reaching the crossover point. 1/total spring rate = 1/ spring rate of first spring + 1/spring rate of second spring. 

Though multiple test rides and by changing the heavier spring and crossover point I ended up with an initial spring rate of 34 lb./in for first 2 ¾ inch fork travel and 60 lbs./in spring rate final 1 ¾ inch fork travel in my Roadster forks. This close to the 35/50 spring rate of the Progressive fork spring, but the 60 lb. final rate reduces bottoming and fork dive caused by my 240 lbs.. 

Compression and rebound damping will be the next topic. A spring by itself acts like a pogo stick, the harder you jump on it compressing the spring, the farther up in air it throws you because the spring rebounds (extends) with nearly equal force. A spring by itself has a relatively high amount of compression damping built in. It naturally resists being compressed. However, a spring has a relatively small amount of rebound dampening built in because it pushes back with nearly the same force that compressed it in the first place. If you had no damping, the spring would continue to oscillate back and forth forever, not a good thing.

Shocks and forks use oil to create compression and rebound damping needed to suppress spring oscillation. Compression damping reduces how far the spring compresses. Rebound damping reduces how far the spring rebounds (extends). Heavier springs need less compression damping, but more rebound dampening. 

Cheap shocks have no adjustments for damping. 

In order to get shocks that have external adjustments to fine tune compression and rebound damping, you start spending a lot more money. The Progressive 418's have one adjustment for the rebound damping. Ohlins, Works, Penske, WP make shocks that have external adjustments for compression and rebound damping. The best shocks have adjustments for high speed and low speed compression damping in addition to rebound dampening. The more expensive shocks also have a much greater range to adjust preload, and the damping can be changed internally to match different springs. 

High speed and low speed compression damping are fine tuning adjustments which helps the rear tire follow different bumps in the road. For example, if you are riding down a concrete highway and can feel those expansion joints pounding your back, you shock has too much high speed damping. It is too stiff over those bumps and you feel each one up your back. Conversely, slow roller type bumps slowly pitch the bike up and down, sort of like laying on an inner tube in the ocean waves. Being able to reduce low speed compression damping will smooth out the ride. 

Damping in the forks is controlled by holes in the damper rod that oil is pushed though as the forks move up and down. By drilling out the compression holes in the damper rod of my forks, I was able to decrease compression damping because more oil can flow through larger holes. By leaving the rebound holes alone, which are at the top of the damper rod, I was able to maintain a fairly high level of rebound damping in my forks. 
At the bottom are the large compression holes. Stock holes are about 1/16" dia. This is a totally different effect than increasing oil viscosity where both compression and rebound damping are increased at the same time. The small stock holes, especially when combined with HD SE heavy duty oil, cause forks to be way over damped. My forks can move up and down much faster than forks with the standard damping holes, and therefor track the bumps in the road much better keeping the tire in contact with the road.

Shocks have a rubber bumper in them to soften the blow when they bottom out. Good shocks can have such a good bumper, that you won't even feel the shock bottom out. In that case, you will have to use a plastic tie to see how much travel you are using. The rubber bumper in cheap shocks do nothing but prevent a hard metal to metal clunk.

2007.09.29
I aim for rear vertical oscillation frequency of chassis in cycles/min of 140 CPM (cell C52). I am getting...

a 100 lb rider needs 77.5#/in springs
a 150 lb rider needs 89.3#/in springs
a 200 lb rider needs 101#/in springs
a 250 lb rider needs 113#/in springs
a 300 lb rider needs 125#/in springs
a 350 lb load needs 147#/in springs (assumes that this is a 200# driver with a 150# passenger)

Notice that for every 50# of load the springs need to change about 12 lbs/in

At this point my stock roadster shocks with stock Low springs is still the best combination I have found to date.  
I am 200 and I get a rider sag of about 1 1/4 of 3 1/4" total on a 7/8 preload adjuster on full hard and 1/2" of extra preload shim. It takes a really bad bump at stupid speeds to bottom it. The ride is a little firm but plenty acceptable. My wife (140#) rides it with the 7/8 of preload off to give a nice low ride for her short legs.
AW

2007.10.15
Today I talked to Progressive and after some prodding I managed to get the spring rates from the tech. To my surprise the long version of the 13.5" shock has two versions of springs 75/120 and 90-130. The 75-120 is a step function spring rate that changes from the low rate to the high rate at what turns out to be right at a 200 lb rider. This leads to the conclusion that you should only purchase the 75/120 spring if you are in the 130# weight range. All people that weight in the 180# and above (like with passenger) should purchase the high HD springs. People in the 180 - 200# range that ride by themselves only, have to go with the 9" fixed rate spring 90# spring and build spacers to get to the correct rider sag or just tolerate the real bad ride on some surfaces.
The HD spring is a true progressively wound spring.
AW


====== Whittlebeast - On Shocks ======
(supplied by bgavin)

URLs
----
https://en.wikipedia.org/wiki/Shock_absorber \\
http://xlforum.net/forums/showthread.php?t=47542 \\
http://xlforum.net/forums/showthread.php?t=919213 (ricor rear shocks) \\
----


**Definitions**

| Preload | Amount of spring compression, measured in pounds per inch of compression |
| Sag | Amount of suspension travel consumed by mounted rider in full gear.  Set to 33% of full travel. |
| Travel | Total linear length of shock movement, eye-to-eye |
| Eye | Upper and Lower shock mounts |
| Full Extended | On center lift or cresting a hill at high speed |
| Full Compress |  |
| Coil Over | Motorcycle shocks when the spring coils are mounted around the shock absorber. |
| Coil Bind | Maximum spring compression where all coils touch. |
| Twin Tube | Inner(pressure)/Outer(reserve) tube where hydraulic fluid is forced between the two tubes. |


2007.02.27\\
So far I have found that the stock 1200 low springs are about 99 lbs/in The springs are 1.7" ID with 13.25 free coils and .279" wire dia. Installed on the bike they are about 6.85" with the shock eye to eye at 11.53" Just over 11.25" with most of me on the bike. Spring free length 9.33" Installed the spring length is 6.85". All this gives 2.48" preload 2.48" x 99#/in = 245 lbs pre-load at full extention per side. Fully compressed and touching the bump staletto, the shock center to center is 9.75" or 1.78" total available shock travel. The rebound damping on the stock shock appears to be way tighter than the 1200s shocks even on full hard. All this data is very bad from a handling standpoint. Normaly you only want enough rebound damping to control the spring from overshooting the static ride height on a rebound.

stock 1200s springs are 51 lbs/in and the free length is 10.25" The springs are 1.93" ID with 12.5 free coils and .270" wire dia. Installed on the bike they are about 7.75 and about 6.5 with most of my 200 lb butt on the bike. This leads to the stock shocks has about 383 lbs total on the rear or about 191 lbs on each shock. Extended the shocks are 13.25 eye to eye. Total shock travel is 2.37" or 13.25 - 2.37 = 10.87 fully compressed to the bump steletto. About 12" with me on the bike. The unladen height of the seat with these shocks is 28.5" or about .5" higher than the Harley claimed height.

After riding the bike ... My first impression is that the stock 1200 Low way too much preload for any smaller rider and I am suspect for all riders. The stock shocks have way too much rebound damping in an attemp to soften up the slam against the shock as the springs recover from a large dip. The solution appears to be regaining some of the travel by installing shocks with longer travel. Sence I started this endever I ran across a Progressive shock number 412-4210c that is 13" eye to eye, has 3.8" of total travel at the shock giving about 4.5" of available wheel travel. The spring rate is a 75/120 that should be about correct for a single 180-200 rider. I have no idea what the preload on this shock or what the valving is like to give much more input. In time I may pop for a pair just to try.

The new Caddies will be here in a few days and I will install the spare sportster sport springs on them. I want to get back to the original Low ride height with a 160# rider with more available shock extension travle and with springs in the 50#/in range. I also hope to try the stock 85# springs in the Caddies as the preload will be only about 1.33" or about 113 lbs preload. The ID of the springs is not real interchangable and may become an issue.

If you measure from the bottom of the drive belt adjusting thread to the front point of the rear tail light I get stock 1200 Low is about 11.25" With the new rear 1200s shocks I get 13.37" or just over 2" higher with no rider.

(added 2/28/07) I laid out the rear suspension in CAD and the motion ratio is about .847 so the total rear suspension travel on the stock Low shocks is 1.78/.847 = 2.1" vertical chassis travel. The 1200s setup is 2.37/.847= 2.8" vertical chassis travel. Normally a chassis is set up to have zero spring preload at full droop and just touch the bump stops on the largest you would ever expect to hit and and use 1/3 of the available at rest with the "normal load". The stock Harley is a far cry from this goal.

(added 3/1/07) I put plastic wire ties on the shock shafts front and rear. Then went for a ride. What I found is that with me at 200 lbs, the 1200s shocks are using the entire available travel. I never felt the rear end hit hard so I am most likely close now, I am suspect that having a spring in the 85# range and with a free length of about 9" requiring less preload would be even better. In the front the standard setup appears to be close. I also noticed that about 33% of the riders weight goes on the front tire and about 66% goes on the rear tire.

AW\\
* * * * * * * *


2007.03.17\\
Generally dive in a motorcycle is not a problem. Running out of suspension at either end of the shock travel is.

Shock travel should almost never be controled by the shock. Travel should always be controled by the spring.

Shock damping is just there to provide as little damping as required to keep the chassis movement from over shooting and bouncing. Shocks are not there to control total travel.

Shocks have two types of resistance in compression "low speed damping" and "high speed damping". 

High speed damping controls when the tire hits things like a speed bump. Low speed damping is things like a big dip in the highway. Extension damping only controls bounce or overshoot as the tires recovers fron a bump. 

Think of extension damping as the thing that only controls the spring. Compression damping controles the ride. Most of the time if you take the spring off the shock and pull in and out with your hands the resistance of the shock should be about the same going in and out. If you end up with way more of one that the other you must be trying to cover one problem with some other problem. Harley on the Low bikes is trying to cover up for too little extension travel with too much extension damping. Ride fast in fast bumps and the chassis will jack down or lower as you go thru the bumps.

If when trying to follow the above rules you end up with too tight of springs for comfort then you do not have enough suspension travel. Add shock travel and start over.

There is no such thing as upgrading springs. What you can change is spring rates and preload. The trick is knowing what direction to go. It is impossible for the shock guys to help you if their first question is not "what problem are we trying to solve. If you dont know what the problem is, you can't answer his first question. I was horified the first time I rode my 2007 1200 Low and have since spent about $600 getting parts and pieces off e-bay to have parts to test with. I now have setups for both me and my wife, one up and two up. And the bike only has 150 miles in it. I am close now and could do this on e-bay now for about $200 with combinations of Harley parts. I have not found the front suspension that much of a problem. The rear was a mess from the factory.

For a great schooling in suspension design, watch the motorcross pros on TV and then reread the above rules several times during the program. Every lap will make this more clear. I helped the Bigfoot monster truck team design and sort out their 10000 lb race truck and I have done chassis design for 700# 2 Gee winged autocross cars. This is all the same.

Google "Motion ratio" "shock tuning" "motorcycle shock tuning" for plenty more info.

Harleys try to break every one of these rules. Follow the rules and all is good.

Hope this helps

AW\\
* * * * * * * *


2007.03.19\\
Here are the shock dimensions that I got with the 1200 Low springs on the 1200 R shocks

shock length fully extended 13.25"\\
...you are in this range any time you crest a hill at high speed the trick is to keep the tire on the road at all cost\\

shock length with bike straight up no rider weight 12.1"\\
...you are in this range every time the road goes down, it happens just as often as the road goes up\\

shock length with a 200# rider 11.4"\\
...you are in this range right after a raised or rising bump, This is all spring rate trying to save hardware.\\

shock length fully compressed 10"\\
...mechanical limit of the shock travel\\

shock length with the bike on the kickstand 12.5"\\
...this is a bling thing. not significant for handling

As you can see the bike with driver is very close to a Low but I have the full 3.25" (about 3.8" at the chassis) of suspension travel available for softening out the bumps. The bike behaves far better crossing both small rapid bumps and large long humps. The thing Harley had screwed up was the lack of suspension droop with the factory Low shocks. A function of way too little shock travel and way too much spring preload. Looking at the Progressive shock charts I would think may of thair available combinations have similar issues.

Hope this helps people sort out thair suspensions to get the ride and look they are looking for. You do not have to have a bad ride to get a good look. I can now jumb back a forth from my Honda ST1300 to the Harley and they now feel very similar in the spring, damping and ride. Bumps are just not a problem. When I got the bike I literaly could not see the road from my head bouncing to the road bumps. The feel of the shock bottoming out on the Low and Custom bikes is realy the shock topping out on bumps. I can't beleve that this ever got past the Harley test riders.

AW\\
* * * * * * * *


2007.03.20\\
Here is a simple series of steps to get to your goal.

Pick a shock that has the most possible available stroke that when in the most compressed position will provide enough clearance for wires, fenders and other expensive things that the tire or belt may contact OR set this up so that you are 1 1/2" below the ride height that you are looking for. Measure this totaly compressed length at the lower of these two points in the suspension travel. We will be aiming to only get the shock to this point at the bigest bump you ever intend to hit. Hopefully you can find a shock with around 3" of availible stroke.

Next you need to find a spring that with the shock at full droop can be installed on the shock by hand. This guarentees that at full droop the spring has no more energy that needs to be controled. With a sportster and with a rider in the 140 lb range the spring will end up at about 75# per inch. At 250# I would expect the spring rate to end up in the 140#/inch range. The spring rate needs to now support the bike and you so that there is still about 1 1/2" available shock travel to deal with bumps. Air shocks may be an option but I have never had a set to play with. They still need to meet these rules.

AW\\
* * * * * * * *


2007.04.20\\
I rode about an hour or so with my wife on the back of the bike about 340# for both of us combined. I only noticed hitting the bump stops once. That was with the Low springs on R shocks. They were set on full preload plus about 1/2 inch. I built 1/2 inch rubber preload spacers the sit up in the top chrome caps.

AW\\
* * * * * * * *


2007.09.18\\
Basically, preload is used to fine tune ride height (also called rider sag) to better match the weight of the rider to the movement of the spring. For example, if you are going to carry a passenger, tightening up the preload can keep the suspension from sagging too low and prevent bottoming out on the bigger bumps in the road. It is used to set the ride height (rider sag) of the supension at 1/3 to 1/4 of the total suspension travel. It can be used to determine if the spring is too heavy or too light for the rider's weight.

Preload in forks is set by the spacer length. The preload for shocks is set by rotating the preload adjuster.

All shocks and forks have a fixed amount of total travel. The travel is measured as the distance from full extension (topped out) to full compression (bottomed out). When you sit on the bike, you generally want the forks or shocks to compress about 1/3 to 1/4 of the full travel. You need this sag to allow for the suspension to travel both up and down from that point.

The maximum travel of the shock body (or forks) may or may not be the same maximum travel the spring is capable of, and travel may also by limited by chasis design, ie tires rubbing. But we will ignore that point for now.

What happens when a heavy rider sits on a shock with a spring that is too light? The spring cannot support his weight and compresses too much. Instead of rider sag at 1/3 travel, he may compress the spring to 3/4 of the available travel. Lets say he weighs 300 lbs, but he has a 100 lb/in spring with 4 inches of total travel. When he sits on the shock with no preload, he compresses the shocks 3 inches and has only 1 inch of travel left over to absorb road bumps. Every bump in the road 1 inch and over in height makes the shock bottom out, very uncomfortable. Once the spring is fully compressed, it then rebounds (fully extends) with close to equal force. This is what throws a rider off the seat. Nightster riders are finding out how bad 1 inch of travel is.

So he gets out the preload adjusting spanner wrench and starts cranking in more preload. By doing this, he is putting the spring under pressure. We can't measure the pressure, but we can measure the distance the spring is compressed. With no load on the spring it was originally 4 inches long. By adding preload, he has now compressed the spring to 3 1/2 inches. That 1/2 inch is the same as 50 lbs of force on the spring. When he sits on the bike, it now compresses only 2 1/2 inches (rider sag)instead of the original 3. Still too much rider sag, he needs to get to only 1 inch rider sag, so he cranks in even more preload.

If he cranks in 1" of preload (100 lbs of force on the spring), he gets 2" rider sag. Still too much sag.

If he cranks in 2" of preload (200 lbs of force), he gets the 1" of rider sag he is looking for.

But look what happened to the spring. While sitting on the bike, it has only 2" of travel left. (He wants to get the full 3" of travel beyond the 1" rider sag.) But that is only half of his problem. Since the spring is now preloaded with 200 lbs of force, it now takes 201 lbs of force to even get the spring to move and it will now take 300 lbs of force to get the spring to move the first full inch. Unfortunately, it will only take another 100 lbs of force to get the shock to bottom out. This is one lousy ride, as soon as he get the suspnsion moving, it is already bottoming out.

What he needs is a 300 lb spring with 4" travel. With zero preload, he will get his 1" rider sag, and still have 3" travel left over to absorb road bumps.

Time out for Whittlebeast to edit and check my math and reasoning. If you guys are able to get through about another page of reading, you will be able to argue with any sales clerk about your suspension. Don't bother argueing with the engineers, they never let you win.

Now we will talk about progressive springs. A progressive spring is described with two spring rates, such as 75/120 lbs/inch. For our initial discussion, we will state the 75 lbs/in rate is the initial rate which controls the motion of the shock for the first 1 inch of travel. The 120 lb/in is the final rate which controls the motion of the shock for the last one inch of travel. The middle one inch of travel has a spring rate that progressively increases from 75 to 120 lbs/in.

The main advantage is that progressive springs provide a softer ride over 1" bumps in the road, but quickly stiffens up to reduce bottoming over 3" bumps in the road. You get the best of both worlds, well not quite. The question becomes just exactly where is that transition point where the progressive spring crosses over from the soft / low initial rate to the hard / high final rate.

We will assume the 75/120 spring rate on a 13 " shock is for the 180 lb rider. But if we put our 300 lb rider on these shocks, he will blow through the compression stroke even faster because of the lighter initial rate. If you watch the spring coils compress as the over weight rider sits on them, you will see the coils in the soft part of the spring bind up (also called stack) against each other. He never even feels the soft initial rate. If we put a 120 lb rider, she will feel an even stiffer ride because both the initial and final rate are too stiff for her.

Adding too much preload to a progressive spring can do the same thing the heavy rider does. It is possible for the preload to coil bind (stack) the initial part of the spring before the rider even sits on the bike. This is why it is critical to get the proper initial rate of a progressive spring, and then use only the minimum preload needed to achieve the correct rider sag.

Now lets say Mr. Know Nothing About Suspension McKool wants that cool looking lowered look that a 11" shock provides. In just a few hundred miles he will realize that stock HD shock is really miserable. It is not uncommon for Harley supension components to have the wrong spring rates and really bad damping curves. Harley tends to take the same shock body, shorten the shaft of the shock and then stick on whatever spring they have an excessive inventory of. A typical example is the 1" shock travel found on Nightsters. So he goes to the Progessive Suspension company website and finds the 11" 412-405B/C shock has 1.9" of travel, almost double the stock travel. But the spring is 90/130 lbs/in. A shorter shock must have a stiffer spring to compensate for the shorter travel. Problem here is that his initial rate has gone up from 75 to 90 lbs/in. That makes the ride even stiffer. This is the compromise riders with short travel suspensions must make.

When you buy a standard shock, changing preload is the only adjustment you can make. However, Works Performance sells what is called Dual Rate springs for forks and shocks. There are actually two separate springs, one stacked on top of the other. One spring has a soft rate, the other a hard rate. The initial spring rate is the combination of both springs compressing together. There is a metal tube inside the high rate spring which limits its travel. When the high rate spring is bottomed out against the metal tube, also called crossover spacer, the spring rate changes from the low initial rate where both spring were compressing, to the final rate which is now the softer spring compressing by itself. The big advantage with Works Dual Rate sping kit, is that you can change springs to give you the initial and final rate you want, as well as control the crossover point by changing the length of the crossover spacer. There is a formula to calculate the actual initial spring rate that results from both springs compressing together before reaching the crossover point. 1/total spring rate = 1/ spring rate of first spring + 1/spring rate of second spring.

Though multiple test rides and by changing the heavier spring and crossover point I ended up with a initial spring rate of 34 lb/in for first 2 ¾ inch fork travel and 60 lbs/in spring rate final 1 ¾ inch fork travel in my Roadster forks. This close to the 35/50 spring rate of the Progressive fork spring, but the 60 lb final rate reduces bottoming and fork dive caused by my 240 lbs.

Compression and rebound damping wil be the next topic. A spring by itself acts like a pogo stick, the harder you jump on it compressing the spring, the farther up in air it throws you because the spring rebounds (extends) with nearly equal force. A spring by itself has a relatively high amount of compression damping built in. It naturally resists being compressed. However, a spring has a relatively small amount of rebound dampening built in because it pushes back with nearly the same force that compressed it in the first place. If you had no damping, the spring would continue to oscilate back and forth forever, not a good thing.

Shocks and forks use oil to create compression and rebound damping needed to supress spring oscilation. Compression damping reduces how far the spring compresses. Rebound damping reduces how far the spring rebounds (extends). Heavier springs need less compression damping, but more rebound dampening.

Cheap shocks have no adjustments for damping.

In order to get shocks that have external adjustments to fine tune compression and rebound damping, you start spending a lot more money. The Progressive 418's have one adjustment for the rebound damping. Ohlins, Works, Penske, WP make shocks that have external adjustments for compression and rebound damping. The best shocks have adjustments for high speed and low speed compression damping in addition to rebound dampening. The more expensive shocks also have a much greater range to adjust preload, and the damping can be changed internally to match different springs.

High speed and low speed compression damping are fine tuning adjustments which helps the rear tire follow different bumps in the road. For example, if you are riding down a concrete highway and can feel those expansion joints pounding your back, you shock has too much high speed damping. It is too stiff over those bumps and you feel each one up your back. Conversely, slow roller type bumps slowly pitch the bike up and down, sort of like laying on an inner tube in the ocean waves. Being able to reduce low speed compression damping will smooth out the ride.

Damping in the forks is controlled by holes in the damper rod that oil is pushed though as the forks move up and down. By drilling out the compression holes in the damper rod of my forks, I was able to decrease compression damping because more oil can flow through larger holes. By leaving the rebound holes alone, which are at the top of the damper rod, I was able to maintain a fairly high level of rebound damping in my forks. Here is a picture of the damper rod sold by Progressive Suspension:

Quote:
http://www.jpcycles.com/productgroup...ore=All&page=1
At the bottom are the large compression holes. Stock holes are about 1/16" dia. This is a totally different effect than increasing oil viscosity where both compression and rebound damping are increased at the same time. The small stock holes, especially when combined with HD SE heavy duty oil, cause forks to be way over damped. My forks can move up and down much faster than forks with the standard damping holes, and therefor track the bumps in the road much better keeping the tire in contact with the road.

Shocks have a rubber bumper in them to soften the blow when they bottom out. Good shocks can have such a good bumper, that you won't even feel the shock bottom out. In that case, you will have to use a plastic tie to see how much travel you are using. The rubber bumper in cheap shocks do nothing but prevent a hard metal to metal clunk.

Many thanks to Whittlebeast for helping me write all this.

XLXR\\
* * * * * * * *


2007.09.20\\
The definition of motion ratio is (vertical wheel movement)/(change in shock length)

1) jack up the bike\\
2) remove the shocks\\
3) let the tire drop to the ground and measure what the shock lenth would be if it was there. say 13.5"\\
4) raise the tire exactly some amount of distance say 4"\\
5) now measure the new shock length say 10"\\

the motion ratio = 4" / (13.5" - 10") = 4" / 3.5" = 1.14

AW\\
* * * * * * * *


2007.09.29\\
I have made a few huge changes to my motorcycle suspension calculator. The first thing I did was add the chassis rideheight when you are cornering at .75 gees. What I found is the added load supported by the springs was enough to callapse the springs in a corner. .75 gees is about the max cornering limit of a of a typical street car. .75 gees is when the bike lean angle is 38 degrees from vertical. Note that 1 gee is 45 degrees lean angle (about what a sport bike can do)

The other big change is you can enter your weight and then follow the directions in the purple box and it will find the spring rate required for your bike.

Please note that this all assumes that you have at least 3" of shock travel and can get to a rider sag of right at 1". This is the least shock travel that I feel is enough to get a quality ride and still keep the chassis off the stops in corners and on the fairly large bumps. The Sportster Roadster (the best suspension that Harley offers on a Sporty) has about 1" less rear suspension travel than what the high tech sport cruisers use. The Nightster only has 1.25" of rear suspension travel stock and rides like it.

Feel free to play with it and ask any questions you want. You can change any numbers that are yellow. White cells are calced on the fly. Orange cells are critical output.

I aim for rear vertical osolation frequency of chassis in cycles/min of 140 CPM (cell C52). I am getting...

a 100 lb rider needs 77.5#/in springs\\
a 150 lb rider needs 89.3#/in springs\\
a 200 lb rider needs 101#/in springs\\
a 250 lb rider needs 113#/in springs\\
a 300 lb rider needs 125#/in springs\\
a 350 lb load needs 147#/in springs (assumes that this is a 200# driver with a 150# passenger)\\

Notice that for every 50# of load the springs need to change about 12 lbs/in

AW\\
* * * * * * * *


2010.11.02\\
Adding spacers does not change the stiffness as that is a function of the weight supported by the spring and the stiffness of the spring. If neither of those things change then there is no change in stiffness.

Changing the spacer or moving the preload adjuster only changes the ride height and how hard you hit the stops when you do hit them running out of travel at the top or bottom of the shock.

AW\\
* * * * * * * *

====== Sportsterdoc - On Electrical ======
(supplied by Sportsterdoc)

Over the past 4 years, I find myself posting much of the same info regarding electrical issues or basic troubleshooting.   To save time, I have saved a few documents, from which to cut and paste.   
As the documents increased, I thought it easier to put most in just one document…which I am sharing, below.

| State of Charge (AGM battery) ||
| 12.8+ | 100% |
| 12.6 | 75% |
| 12.3 | 50% |
| 12.0 | 25% |
| 11.8 | Zero |

**Voltage Readings**\\
1. KEY OFF battery voltage, at the battery:  Normal is 12.8.\\
If just taken off a charger, voltage may be 13 point something. The battery needs to sit for a while (or turn on the key for ~3 seconds, then turn off) before a reading is useful.
In the case of a bad cell, the other cells overcharge and give an almost normal reading, until load is applied.\\
• If lower, then battery is discharged and needs charging or\\ 
• Battery has a bad cell\\

2. KEY ON battery voltage (headlight on): Normal is not under about 12.5 initially, but will decline the longer  the headlight is on, without the motor running. Under no load, 12.5 volts indicates severe discharge, but under headlight load, it is just voltage drop.\\
• If lower, then battery is discharged and needs charging or \\
• Battery has a bad cell or\\
• Battery cable(s) have high resistance\\

3. KEY ON battery voltage while cranking: Normal is not under 10.5 volts\\
• If lower, then battery is discharged and needs charging or\\
• Battery has a bad cell or\\
• Battery cable(s) have high resistance or\\
• Starter is drawing too much current\\
• Solenoid contacts have high resistance\\


4. If the bike is running, battery voltage at about 2,500 RPMs should be 13.8 to 14.8\\
• If not, then check stator resistance and regulator ground\\
• If the stator is not shorted to ground and resistance is within spec, the regulator or regulator ground is suspect\\

5. When there is a problem with “no power” check the 30 amp circuit breaker or maxi fuse between the battery and the keyed switch and all the 15 amp fuses after the key switch (or circuit breakers on many Ironheads). If circuit breakers / fuses are OK, then measure voltage coming into the key switch and continue downstream until the voltage stops.\\


**Coil Testing**\\
Dual fire coil testing, typical for Ironheads and Rigid EVO, (except for Sportster Sport 1998-2003) and the last three years of the carburetor / first three years of the Rubsters (2005-2006)
Coil has two primary screw terminals (+ & -) with twin coil towers. Beginning in 1999, the coil (31655-99) primary is connectorized (this coil is utilized through 2006).
 
Primary resistance is measured from + to - terminals, at 2.5 to 3.1 ohms (31655-99). 
Secondary (high voltage) winding resistance is tested from coil tower to coil tower, specifications vary, typically in the range of 10,000 ohms to 12,500 ohms. Check the FSM for primary and secondary coil resistance for your year.

Single fire coil testing, typical for for Sportster Sport (1998-2003)
Coil (31646-99) has three connectorized primary terminals (- + - ), referenced A (front) B (12 VDC) C (rear) and twin coil towers. This coil is two coils in one, with primary terminal B common.

Primary resistance is from + to -, both B to A and B to C at 0.4 to 0.6 ohms. For the 1200S (dual plug heads), measure secondary resistance between both front coil towers and then between both rear coil towers (each should measure 11.7K to 12.7K ohms).

Single fire coil testing for EFI Rubsters, 2007 and up (with input from Cosmo Kramer):
Coil (31656-07) has 4 primary terminals, referenced, left to right, as A (+), B (+), C (rear) & D (front).

A or B to D should measure 0.3 to 0.7 ohm and A or B to C should measure 0.3 to 0.7 ohm.
Secondary resistance: 1,500 to 2,400 ohms, tower to tower

Note: If resistance is lower than specified, that winding has partially shorted, bypassing part of the coil. If resistance is higher, then corrosion or failing internal connections may be adding to the resistance.

**Sportster CKP Testing**\\
Sportster crank position sensors are 2 wire units, which may be described as variable reluctance sensors or magnetic pulse generators, etc. They do not have as clean a signal as hall effect, but generally more durable (simple coil). As with the hall effect, they are typically rated -40 C to 150 C (300F).

For 2004-2006 Sportsters, the voltmeter red lead is connected to ICM position 8 and the black lead to ICM position 9.

For 2007-2013 Sportsters, the voltmeter read lead is connected to ECM position 30 and the black lead to ECM position 12.

Note:  This is a sine wave and requires the AC scale\\
While cranking: ~ 0.3 VAC \\
At idle: ~ 1 VAC\\
Static: N/A\\

When your bike is not starting, this basic test will validate a functional CKP or indicate a failed CKP. A failed unit will not provide a signal. However, this is not sufficient to test for a failing unit with inconsistent output.

**Spark plug secondary cable testing**\\
Most electronic ignition module manufacturers recommend 3,000 ohms per foot, although some “high performance” cables are less.

**Bank Angle Sensor (BAS) Bypass, prior to ICM, ECM models**\\
The BAS (under the “ignition” triangle cover) has three wires and receives power from the gray wire (from the ignition fuse) which also powers the “engine stop/run switch”. If removing the sensor, that 12 VDC wire will need to be capped. Connecting the light green/gray wire (from the module) to ground, via the black wire, will provide run mode.

**Ignition Module Bypass**\\
The ignition module closes the coil primary circuit to ground.   Based upon a timed signal from the cam sensor, the module opens the primary circuit, causing the secondary (high voltage) winding to discharge through the plugs to ground.

To verify that wiring and other components (coil, plug wires, plugs) are OK, when a failed/failing ignition module (pre 04) is suspected, try this:  Pull the coil wire (at the coil) to the module (not the 12VDC to the coil primary).   If connectorized, pull the connector, then jumper 12 VDC to the + side of the coil.   

Note:  The coil has no actual polarity. + & - are irrelevant, but + denotes incoming voltage and – denotes side to be grounded through the module. In other words, do not ground the incoming voltage without the load/resistance of the coil

Ground the ignition module side of the coil (-), then remove ground, expecting one spark (plug out of head, in secondary wire, plug prong grounded). If done correctly and no spark, then the problem is NOT the module.

**Stator and regulator testing**\\
Measure stator resistance to ground (∞) and stator resistance (0.1 to 0.5 ohm, depending upon system), pin to pin.\\
22 amp system ~ 0.2 to 0.4 ohms\\
32 amp system ~ 0.1 to 0.2 ohms\\

If you have a diode setting on your multimeter, you can use this test sequence adapted from JPCycles.

Generally, I just figure that if wiring (double check regulator ground)and stator check OK, blame the regulator.

Regulator Test: Each of the following tests isolates the regulator only, so if any of these tests fail, the regulator is at fault.

Identifying Wires:\\
Battery Charge Lead– Wire going from regulator to battery positive.\\
AC output leads– Wires coming from the Stator to regulator.\\
Ground– Wire from Regulator to ground or regulator may be grounded via the physical bolting to chassis.\\

Regulator Ground Test: Insure the regulator body is grounded or grounding wire is fastened tight to a good ground (you should verify this by checking continuity from regulator body to chassis ground).

Fwd/Reverse Bias Test/Diode Test: This check is testing the Diode function to ensure it is regulating the AC current for the stator into DC Current.

Switch multi meter to Diode Scale.\\
Place your Multi meter positive lead on each AC output wire.\\
Place your multi meter negative lead on the battery Charge wire.\\
The meter should read voltage typically around .5 volts.\\
Next, switch your multi meter leads putting the negative lead on the AC output wires and the Positive lead on the Battery Charge Wire.\\
The reading should be Infinite.\\
With your meter on the same setting, place your multi meter positive lead on the regulator ground wire or to the regulator directly, and then place your meter negative lead on the AC output leads.
The meter should read voltage typically around .5 volts.\\
Next, switch your multi meter leads putting the negative lead on the regulator ground and the Positive lead on the AC output wires.\\
The reading should be Infinite.\\

**BASIC TROUBLE-SHOOTING SEQUENCE**\\
When the key and stop/run switches are on, but starter does not operate/no electrics, check voltages and insure that there is voltage past the keyed switch to all the fuses. 

If the battery is good, the keyed switch has no voltage drop, the fuses are good, then battery cables are a common problem. Check (inspect/tug) BOTH ends of BOTH battery cables, especially the frame/motor end of the negative cable.

When a bike won’t start and yet the motor will turn over (starter will crank), my typical approach is –

1. Does it kick over “normal”? The first 10 of my 13 bikes had kick starts and it was easy to feel the compression. Without that feature, pull the plugs and put a finger over the plug hole while cranking. If you’ve had the bike a while, the amount of pressure should feel normal. If you have a compression tester, all the better. If rings are not excessively worn, no hole burned in piston and valves operated normal, then move on to the next step.

2. Were plugs wet, when pulled, after trying to start? If not, check for fuel flow (does accelerator pump squirt?...if not (and pump diaphragm is intact), then check if -\\
a. petcock screen not clogged?\\
b. fuel tank cap venting?\\
b. petcock flowing (vacuum connected on the vacuum operated)?\\
c. fuel in bowl (open drain screw [N/A on 1200S] is quick way to check)?\\
d. if a-c are OK, then remove carb bowl and check float valve not restricted with debris\\
e. float level correct?\\
f. If unsure, does starter fluid get it going? If so, then it is a fuel/fuel mixture issue. If you have fuel, then move on to the next step.\\

3. With plugs out, plugs in high voltage boots, plug prongs grounded (typically to cylinder/head cooling fins), kick the motor or operate the starter. Check for strong bright blue spark. If none, or weak, then check -\\
a. voltage to coil primary (should be same as battery voltage)\\
b. measure coil resistance\\
c. check high voltage plug wires (both ends)\\
d. check spark plug condition\\
e. check coil primary connection to points/ignition module/ICM (04-06)/ECM (07-13).\\
f. If EVERYTHING checks good, but still no spark, then it may be the points/condenser or nose cone ignition module/cam sensor (thru 03)/or the crank position sensor (CKP) 07-up.\\

**Electrical maintenance**\\
Check BOTH ends of BOTH battery cables: Inspect, tug

For 2007-2009, especially:\\
Remove chassis/harness ground (top of trans, clean external and internal threads, apply copper based (conductive) anti-seize and reinstall. Or at least measure resistance from top of chassis ground wire lug to battery negative post. Should be 0.1 ohm or less.\\
Pull maxi fuse, remove all fuses, clean front and back of fuse block. Reinsert fuses, reinsert maxi fuse.\\
Replace system relay if more than ~ 2 years old, less if parked or ridden in rain.\\


====== Screw Loose Dan - Rubbermount Jiffy Stands ======

Jiffy stand (aka kickstand) measurements for rubber mount Sportsters.

Since most folks wanting to compare jiffy stands are concerned with lean angle when resting, I measure them from the pivot point to the point they touch the ground, I deem this the "Useful Length".  The rough measurements can be made either on or off the bike.  Either will get you in the neighborhood.  The toe kick part of the jiffy stand can add significantly to the overall length.

For example here is a jiffy stand on/off the bike being measured (not sure what this stand is):
{{https://screwloosedan.com/cm/albums/userpics/10001/combine_images.jpg}}

In either case, you can see that the stand is ~10.5".

Here are some measurements I've taken:

^ PN ^ Useful Length (in) ^
| 50124-09BHP |  ~9.6  |
| 50238-07BHP |  ~6.3  |
| 49722-07BHP |  ~10  |
| 50185-04 |  ~8.5  |

Pictures of these measurements can be seen in [[http://xlforum.net/forums/showpost.php?p=5664721&postcount=7|this post]].

====== Trickle Charger ======

\\ 
Destination: Ref-Electrical

|  Trickle charger pigtail location on 98 model ((photo by Hippysmack))  |  Trickle charger below & to the rear of the battery box on 94 on model ((photo by IXL2Relax of the XLFORUM http://xlforum.net/forums/showthread.php?p=5672190#post5672190))  |
|{{:techtalk:ref:elec:trickle_charger_pigtail_by_hippysmack.jpg?direct&400|}}|{{:techtalk:ref:elec:trickle_charger_pigtail_by_ixl2relax.jpg?direct&400|}}|

====== Who - Subject ======

====== Who - Subject ======

\\
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