Rebound Adjustment

[3dogs]

I have never seen on this form a description of how to actually evaluate suspension rebound damping adjustments. I did not pull this procedure out-of--my-ass but it comes from "suspension-educated" experts--I'm only the messenger.

Rebound damping controls spring movement or energy. It limits how fast the spring is allowed to move the suspension upwards after compression. Rebound is easy to set up correctly if you know what to look for. The number of clicks out/in does not provide any meaningful description of how much rebound is in the “ball park.” The number of clicks varies between bikes (even the same year and model) because type of suspension oil and age of the oil (looses viscosity over time) all have an effect on rebound damping.

Here is how to evaluate and adjust rebound damping.

1. Stand next to the bike and hold it upright. Apply the front brake. Push down on the front suspension and let the bike “rebound” upwards (keep the bike upright but don’t restrict the upward movement of the suspension).

2. As the front suspension reaches the top of its travel it may bounce up and down (or not). This movement is what you should observe when trying to determine how to adjust rebound.

3. Too Little Rebound; The front suspension will rebound quickly. When the forks reach the top of their travel they will go back down, then back up. The bouncing or oscillation may take from 2 to 4 cycles (up and down) before the suspension movement stops. The “pogo stick” action of the suspension indicates too much rebound. Too much rebound will cause the ride to feel bouncy, like a pogo stick. Each bump encountered will cause the suspension to move and without enough rebound to control the spring energy the front will have excessive movement—upsetting the chassis and causing a lack of control of the bike—especially in corners.

4. Too Much Rebound; The front suspension will rebound slowly. The forks will reach the top of their stroke and stop. There will be no up and down oscillations of the suspension. The ride will feel controlled—However the spring will not be able to extend quickly enough to deal with a series of bumps. The result is what is known as “packing” where the suspension will loose travel on each bump until it bottoms out.

5. The Correct Amount of Rebound; Set the rebound adjustment so the suspension rebounds/extends as quickly as possible without bouncing when it reaches the top of its travel. A slight secondary bounce is OK. This amount of rebound is the correct “ball-park.” If your adjustment is in the ball park, further adjustment is subjective and each rider will have his/her own idea as to what’s ideal.

Note: The rebound adjustment procedure of the rear suspension is the same as the front.

Just because your FJR has a rebound adjustment does not mean that you can get the rebound adjustment correct. Oil viscosity/age, rebound valving all effect the adjustment. In fact, many stock rebound adjusters cannot provide enough rebound damping--a common problem. That’s why Race-Tech and other aftermarket suspension providers are in business.

Even when new, my stock FJR (05) was unable to dial in enough rebound with the adjuster screwed all the way in (no clicks out). I had to replace the Yamaha components with Race-Tech parts and their recommend oil to get rebound to adjust correctly. You can find lots of suspension info in Lee Park’s and Paul Thede’s book “Race Tech's Motorcycle Suspension Bible"

 

[Afast03nNJ]

You do realize that when you put a ~200lb person plus luggage on the bike, everything changes.

 

[ionbeam]

FWIW, the clicks mean nothing and do not relate in any way to the function of the shock. The clicks are simply a detent that lets you determine position between zero and full adjustment range. Do setup your suspension based on dynamic operation. The number of clicks only tells you that for a given load the shock is happy at 12. Add a passenger and the shock may be happy at 17. The clicks just tell you where the adjustment is, not what the adjustment is.

 

[fjrrider]

Good stuff!!

So many times I see someone recommend to another rider suspension settings based on what their own settings are. I guess the reason they do this is that a lot of riders are nervous or intimidated about experimenting with their own suspensions for some reason.

Spending a bit of time riding, adjusting then riding some more would be beneficial to anyone willing to improve the performance of their own bike!

 

[3dogs]

You do realize that when you put a ~200lb person plus luggage on the bike, everything changes.

You are correct. A 200 lb rider will change some things--like what spring rate and preload to use.

However, rebound damping has little to do with the weight of the rider. Rebound is only effected by the spring releasing energy after it has compressed.

 

[RinconVTR]

You do realize that when you put a ~200lb person plus luggage on the bike, everything changes.

You are correct. A 200 lb rider will change some things--like what spring rate and preload to use.

However, rebound damping has little to do with the weight of the rider. Rebound is only effected by the spring releasing energy after it has compressed.

You're right about the weight of a rider not affecting rebound (much). But when you change spring rate (new spring) and even pre-load (adjustment or spacer), rebound settings will change too. It all works in conjunction.

 

[skifrik]

thanks for the info. it's good to get some insight into this.

 

[dsmack]

Good stuff!!

So many times I see someone recommend to another rider suspension settings based on what their own settings are. I guess the reason they do this is that a lot of riders are nervous or intimidated about experimenting with their own suspensions for some reason.

Spending a bit of time riding, adjusting then riding some more would be beneficial to anyone willing to improve the performance of their own bike!

You have just described me to a "T"!

Have to just get over my reticence, and get out in the garage and try to improve it a bit. I guess the best place to start is just count the number of clicks for the present setting... that way I can always return to the present settings if needed.

Thanks for getting mental synapses firing again!

Don

 

[NovaFlyer]

Thank you for posting this as I'm in the process of resetting my suspension after a fork overhaul. I've had this 'po-go stick' action going on up front and was taking stabs in the dark trying different things. I'll try the rebound tomorrow.

On another front. Should we adjust the compression at the same time and in the same direction? The roads around my neck of the woods have all sorts of bumps and heaves in them so presently have the compression on the soft side to try and get a smooth ride. Pre-load is backed off as well.

Any input is welcome.

Thanx again.

NFlyer

 

[fjrrider]

Good stuff!!

So many times I see someone recommend to another rider suspension settings based on what their own settings are. I guess the reason they do this is that a lot of riders are nervous or intimidated about experimenting with their own suspensions for some reason.

Spending a bit of time riding, adjusting then riding some more would be beneficial to anyone willing to improve the performance of their own bike!

You have just described me to a "T"!

Have to just get over my reticence, and get out in the garage and try to improve it a bit. I guess the best place to start is just count the number of clicks for the present setting... that way I can always return to the present settings if needed.

Thanks for getting mental synapses firing again!

Don

I can tell you how I do it, I carry a couple of tools with me, I think its a 14MM wrench, screwdriver and a 17MM for the fork preload. I have aftermarket suspension by GP Suspensions. A Penske shock with low and Hi speed comp adjustments and rebound.

I will go out and find a short section of road somewhere, I use a good twisty section. Ride it, make adjustments, do it again and again. When I think I got it down good, I go back and check stock settings just to see.

I find that what works good for me on twisty roads is not very plush on the slab or over rough road. The point is to check it out for yourself, your not gonna hurt anything, just know where to come back to. Stock settings are in your FJR manual in case you forget.

 

[fjrrider]

Thank you for posting this as I'm in the process of resetting my suspension after a fork overhaul. I've had this 'po-go stick' action going on up front and was taking stabs in the dark trying different things. I'll try the rebound tomorrow.

On another front. Should we adjust the compression at the same time and in the same direction? The roads around my neck of the woods have all sorts of bumps and heaves in them so presently have the compression on the soft side to try and get a smooth ride. Pre-load is backed off as well.

Any input is welcome.

Thanx again.

NFlyer

Your Po-Go stick action most likly needs increased preload on the forks to reduce or eliminate, once you get that done the compression and rebound adjustments will help fine tune the ride!

For me at 6'3" 230, I had to have the forks resprung to correct that pogo action, I couldnt do it with the stock springs.

And you for sure want both forks set exatly the same!

 

[not2shabby]

Thank you for posting this as I'm in the process of resetting my suspension after a fork overhaul. I've had this 'po-go stick' action going on up front and was taking stabs in the dark trying different things. I'll try the rebound tomorrow.

On another front. Should we adjust the compression at the same time and in the same direction? The roads around my neck of the woods have all sorts of bumps and heaves in them so presently have the compression on the soft side to try and get a smooth ride. Pre-load is backed off as well.

Any input is welcome.

Thanx again.

NFlyer

I recently did the RT overhaul and when I went for the test ride with their settings(20 clicks out on comp, 15 for reb I think), I had the pogo stick going on too. I've gone 5 clicks in on reb and it's really nice now. Make sure you have both legs set the same. If you think about it, a stiffer spring should need less comp since it takes more force to start it moving and more reb since it should exert more force when it extends. Of course if you change the valving, you'll need to experiment. Good luck!

 

[NovaFlyer]

Thanx guys. I've wound up the rebound front/back and have noticed an improvement. Now the fine tuning starts when I get some time.

 

[2Bull]

Hi all,

Is there any consensus on what is the best rebuild for front forks? Traxxion and Race-tech I have seen a lot of but is one better than the other? I ride fairly aggressively but nothing too intense and want both a plushness and some substance when cornering. Can this happen?

 

[TahoeBound]

...3. Too Little Rebound; The front suspension will rebound quickly. When the forks reach the top of their travel they will go back down, then back up. The bouncing or oscillation may take from 2 to 4 cycles (up and down) before the suspension movement stops. The “pogo stick” action of the suspension indicates too much rebound. Too much rebound will cause the ride to feel bouncy, like a pogo stick. Each bump encountered will cause the suspension to move and without enough rebound to control the spring energy the front will have excessive movement—upsetting the chassis and causing a lack of control of the bike—especially in corners.

Do you mean "too little rebound" makes it pogo? Too little rebound will cause the ride to feel bouncy?

 

[not2shabby]

...3. Too Little Rebound; The front suspension will rebound quickly. When the forks reach the top of their travel they will go back down, then back up. The bouncing or oscillation may take from 2 to 4 cycles (up and down) before the suspension movement stops. The “pogo stick” action of the suspension indicates too much rebound. Too much rebound will cause the ride to feel bouncy, like a pogo stick. Each bump encountered will cause the suspension to move and without enough rebound to control the spring energy the front will have excessive movement—upsetting the chassis and causing a lack of control of the bike—especially in corners.

Do you mean "too little rebound" makes it pogo? Too little rebound will cause the ride to feel bouncy?

Yes.

 

[Fred W]

And you for sure want both forks set exatly the same!

Really? I've seen this advice repeated and emphasized so often. But is it really so important?

Some newer off road forks like Showa's Seperate Function Fork (SFF) used on some new Kawasaki models, are intentionally designed with spring and dampening actions separated and only in one fork leg each. The concept is that since the two fork legs are solidly joined through the triple trees, any spring or dampening occurring on one side will equally effect the entire fork assembly.

Here's an excerpt from the 2011 KX250F press release:

SEPARATE FUNCTION FORK (SFF) Kawasaki's new Separate Function Fork (SFF) is a revolutionary design, one that allows KX250F riders to easily tune front suspension action for demanding track conditions. Unlike a conventional fork design, where each fork leg handles both springing and damping duties, the KX250F's SFF fork separates spring and damping functions for better overall performance and a higher degree of adjustability. The right fork leg accommodates a large main spring/rod assembly, with preload now easily adjustable via a blue-anodized adjuster in the right cap. The left leg handles all damping duty, and features full rebound and compression damping adjustability.

Sure, if the forks' legs were allowed to move independently of each other having them set-up entirely equal would be ultra important. But that doesn't seem to be the case in modern suspension systems.

Also, consider this: Just turning the adjustment clicker the same number of detents on both sides does not insure you are getting identical dampening. It will be close, but manufacturing tolerances are not perfect, so there will be some variation leg to leg and from bike to bike. Also, since the oil reservoir (fork leg) is separate there can be differences there as well.

 

[fjrrider]

And you for sure want both forks set exatly the same!

Really? I've seen this advice repeated and emphasized so often. But is it really so important?

Some newer off road forks like Showa's Seperate Function Fork (SFF) used on some new Kawasaki models, are intentionally designed with spring and dampening actions separated and only in one fork leg each. The concept is that since the two fork legs are solidly joined through the triple trees, any spring or dampening occurring on one side will equally effect the entire fork assembly.

Here's an excerpt from the 2011 KX250F press release:

SEPARATE FUNCTION FORK (SFF) Kawasaki's new Separate Function Fork (SFF) is a revolutionary design, one that allows KX250F riders to easily tune front suspension action for demanding track conditions. Unlike a conventional fork design, where each fork leg handles both springing and damping duties, the KX250F's SFF fork separates spring and damping functions for better overall performance and a higher degree of adjustability. The right fork leg accommodates a large main spring/rod assembly, with preload now easily adjustable via a blue-anodized adjuster in the right cap. The left leg handles all damping duty, and features full rebound and compression damping adjustability.

Sure, if the forks' legs were allowed to move independently of each other having them set-up entirely equal would be ultra important. But that doesn't seem to be the case in modern suspension systems.

Also, consider this: Just turning the adjustment clicker the same number of detents on both sides does not insure you are getting identical dampening. It will be close, but manufacturing tolerances are not perfect, so there will be some variation leg to leg and from bike to bike. Also, since the oil reservoir (fork leg) is separate there can be differences there as well.

The FJR does not have SFF in case you were wondering.

Do you have a better method of getting both forks set as close to the same as possible, without using clicker counts?

Have you tried setting your fork adjustments different from one another? How did that go?

 

[Fred W]

I know that the FJR isn't SFF. I only bring that up because that is the extreme example of where the two sides are NOT set identically.

And no, I have not intentionally set mine differently. My point was, try as you might to set them identically, they won't be. My conclusion is, I don't think it really matters much (if at all) if the two sides happen to be identical. If you just get the total amount of spring, preload and dampening that you need then it's all good.

If one fork leg happens to have a tad more spring preload or dampening in one direction or the other, you'd never be able to tell because the two fork legs are hard bolted together and work completely in unison.

Edit - Let me just add that, unless the fork triple trees were designed for it, I would not intentionally put all of the spring preload in one leg or all of the dampening in one side as it would probably put undue twisting forces on those trees.