Rebound Adjustment
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ionbeam
2 FUN
I believe that fjrrider thinks you are actually advocating putting spring on one side and damping on the other, or simply intentionally mismatching the two forks.
It was plain to me that you said that a small mismatch between the two fork legs wasn't a problem and then went on to use the SFF as a dramatic example of how extreme the fork leg differences can be and still have a properly working suspension. The only caveat I would offer here is that the SFF is a system designed to work unbalanced, unlike a fork system that is unbalanced by error or failure.
When the forks contain damping cartridges, springs, air dome, oil volume and oil viscosity the forks can never be identically matched. Anyone that has popped a fork seal will only notice the different oil volume by sight of the dripping oil and not fork performance unless both seals failed together. I've never heard of someone stopping their bike and looking for a leaking seal because handling issues.
The forks are mechanically connected by the axle on one end and the triple tree on top creating two damping systems working in parallel. In most mechanical and electrical systems such as parallel springs or parallel resistors the energy difference is divided, thus minimizing any variation from side to side. Many FJR home mechanics have done fork service then run the adjuster from minimum to maximum and discovered that the number of available clicks varies from side to side. Some have reported nearly a 2x difference yet the handling has been just fine.
It was plain to me that you said that a small mismatch between the two fork legs wasn't a problem and then went on to use the SFF as a dramatic example of how extreme the fork leg differences can be and still have a properly working suspension. The only caveat I would offer here is that the SFF is a system designed to work unbalanced, unlike a fork system that is unbalanced by error or failure.
When the forks contain damping cartridges, springs, air dome, oil volume and oil viscosity the forks can never be identically matched. Anyone that has popped a fork seal will only notice the different oil volume by sight of the dripping oil and not fork performance unless both seals failed together. I've never heard of someone stopping their bike and looking for a leaking seal because handling issues.
The forks are mechanically connected by the axle on one end and the triple tree on top creating two damping systems working in parallel. In most mechanical and electrical systems such as parallel springs or parallel resistors the energy difference is divided, thus minimizing any variation from side to side. Many FJR home mechanics have done fork service then run the adjuster from minimum to maximum and discovered that the number of available clicks varies from side to side. Some have reported nearly a 2x difference yet the handling has been just fine.
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wheatonFJR
...
Thanks Alan for the explanation...
I think Scott/fjrrider is not saying setting the clicker settings will make the two tubes act exactly the same...but that you minimize torques created by one tube having different setting than the other.
Yes, the tubes work in parallel, like Alan said, but they act...atleast in one plane...offset from each other, as Fred admits.
I think Scott's subsequent posts were reacting to the apparent cavalier statement by Fred...
I think Scott/fjrrider is not saying setting the clicker settings will make the two tubes act exactly the same...but that you minimize torques created by one tube having different setting than the other.
Yes, the tubes work in parallel, like Alan said, but they act...atleast in one plane...offset from each other, as Fred admits.
I think Scott's subsequent posts were reacting to the apparent cavalier statement by Fred...
That would be a question, not a statement.
And yeah, I was questioning the conventional wisdom, not the poster.
Heretic? Maybe. But not cavalier.
And yeah, I was questioning the conventional wisdom, not the poster.
Heretic? Maybe. But not cavalier.
fjrrider
aka "sprocket"
wheatonFJR
...
As long as we are questioning grammar and that English language stuff...as well as conventional wisdom...which is conventional usually for a reason...
I think that the question posed was a statement. A statement of disbelief...AND I used apparent as a descriptor of cavalier.
You can check your dictionary to determine how that modifies the word following it.
But in realm of this thread on REBOUND ADJUSTMENT...I think Scott's advice helpful...yours...I don't know.
ionbeam
2 FUN
And this is how you tell that a thread has stopped providing useful FJR information for the collective and has become about other things. Stick a fork in it.As long as we are questioning grammar and that English language stuff...as well as conventional wisdom...which is conventional usually for a reason...
I think that the question posed was a statement. A statement of disbelief...AND I used apparent as a descriptor of cavalier.
You can check your dictionary to determine how that modifies the word following it.
h34r: 
TahoeBound
Well-known member
I'll try to bring it back around :lol:
I've gotten some good tips on rebound adjustment and suspension setup overall for my new Race Tech fork springs & their high-dollar fork oil, but the right "feel" has completely eluded me. I am quite unhappy. To the point that today I went to order stock springs because I at least knew I liked them - but much to my dismay I found they are on back order!
I have Preload Sag set at 45mm. I have compression at a middling value of about 12 out. I feel like my rebound is out of whack & it could be the spacers - per Louie at RT I was to cut the stock spacers equal distance of the difference in the new RT's length versus the used stock length - that was about 2 inches. However, the clickers now have a range of about 32 (where stock was around 20).
Freeway ride here in Prunieville is terrible - very busy. Not so much harsh until I get toward max rebound, but very busy. The smoother the road & slower the speeds, the better the suspension. Around town is OK. I also have headshake only at ~50mph & I have a new front tire on order.
I've tried pretty much the entire rebound range from min to max in 2 click increments & nothing feels decent.
Any thoughts? Or anyone have a line on new stock springs?
ionbeam
2 FUN
I didn't see a mention of the compression damping... Bottom of the forks, 12 clicks nominal.
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TahoeBound
Well-known member
A couple more items: RT recommends 2.5-5 wt fork oil (seems light w/factory at 10wt I think). Also, the measured oil height is 110mm from top which is what I measured prior to removing old springs/oil. Everything triple-checked & forks pulled off the bike twice - details appear to be correct.
Now wondering if the spacers cut based on a worn spring is correct. Don't springs "grow" when worn? If that was the case, the spacers would be too short.
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HaulinAshe
Well-known member
Before this spins off into oblivion...
I can fix your RT fork setup for you, or at least I can drastically improve the ride comfort, but I will have to open your cartridges and make some valving changes to do so.
Did you perform the RT install yourself, or did RT do it?
Feel free to email me and take this specific discussion offline.
haulinashe at gmail dot com
Jeff
HaulinAshe
Well-known member
As for SFF or whatever Kawi calls it... They are not breaking new ground with that setup. KTM has been using forks with Rebound on one side and Compression on the other in their small bikes (65 cc) for several years.
It's a system that works well as long as the forks are very rigid, wheel bearings are in excellent condition, steering stem bearings are large and tight, yada yada yada. The big incentive for that separated damping control is the small bikes where space is a premium. In larger forks/bikes, it can be a weight saver that matters in racing conditions where each gram is a precious savings. But personally, I don't see the justification for the service requirements in most street applications.
IMHO there's too much risk of improper service (or lack of increased service intervals) leading to problems. The advantages are simply not worth the increased risks and increased service requirements IMO.
It's a system that works well as long as the forks are very rigid, wheel bearings are in excellent condition, steering stem bearings are large and tight, yada yada yada. The big incentive for that separated damping control is the small bikes where space is a premium. In larger forks/bikes, it can be a weight saver that matters in racing conditions where each gram is a precious savings. But personally, I don't see the justification for the service requirements in most street applications.
IMHO there's too much risk of improper service (or lack of increased service intervals) leading to problems. The advantages are simply not worth the increased risks and increased service requirements IMO.
HaulinAshe
Well-known member
And one more thing... (Ya'll knew it was coming, didn't you! )
I have objection with the very title of this thread and the implication that "counting clicks" is NOT how to properly adjust Rebound.
If you have ever looked inside a typical cartridge fork setup (like the FJR) you will find a long steel rod (or tube) that moves against a spring-loaded Rebound control needle. It's sole purpose in life is to hold the control needle at a fixed distance from the needle seat or venturi opening. The way you accurately gauge that setting, taking into consideration all the various and possible mechanical tolerances and differences, is to GENTLY and FULLY seat the needle (Clockwise), then COUNT THE CLICKS CounterClockwise to obtain a fixed and measurable opening/distance.
Doing so matches the opening on both sides as accurately as mechanical settings can provide. If you want to be any more accurate, the forks must be placed on a dyno and be measured/matched.
It's just like setting a mixture screw on a carburetor. You always count the turns from fully-closed/CW. There's nothing different about Rebound clickers, except it has "clicks" to help measure increments of rotation.
)I have objection with the very title of this thread and the implication that "counting clicks" is NOT how to properly adjust Rebound.
If you have ever looked inside a typical cartridge fork setup (like the FJR) you will find a long steel rod (or tube) that moves against a spring-loaded Rebound control needle. It's sole purpose in life is to hold the control needle at a fixed distance from the needle seat or venturi opening. The way you accurately gauge that setting, taking into consideration all the various and possible mechanical tolerances and differences, is to GENTLY and FULLY seat the needle (Clockwise), then COUNT THE CLICKS CounterClockwise to obtain a fixed and measurable opening/distance.
Doing so matches the opening on both sides as accurately as mechanical settings can provide. If you want to be any more accurate, the forks must be placed on a dyno and be measured/matched.
It's just like setting a mixture screw on a carburetor. You always count the turns from fully-closed/CW. There's nothing different about Rebound clickers, except it has "clicks" to help measure increments of rotation.
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3dogs
Well-known member
The reason I can up with the title "Real Info on How-to-Adjust (no counting clicks)" is because too much is made of counting clicks and the actual results of observed rebound adjustments (see first post for directions on how to do this) are almost never mentioned. The clicks are only a reference. Because our FJR’s use different oil weights and brands AND have differing amounts of mileage on them (oil viscosity changes with use), offering each other advice on how many clicks out is the correct (or even in the ball park) rebound adjustment is simply pointless.And one more thing... (Ya'll knew it was coming, didn't you!
I have objection with the very title of this thread and the implication that "counting clicks" is NOT how to properly adjust Rebound.
If you have ever looked inside a typical cartridge fork setup (like the FJR) you will find a long steel rod (or tube) that moves against a spring-loaded Rebound control needle. It's sole purpose in life is to hold the control needle at a fixed distance from the needle seat or venturi opening. The way you accurately gauge that setting, taking into consideration all the various and possible mechanical tolerances and differences, is to GENTLY and FULLY seat the needle (Clockwise), then COUNT THE CLICKS CounterClockwise to obtain a fixed and measurable opening/distance.
Also it is pretty anal to worry about both sides being equal as the fork tubes are mounted in upper and lower triple clamps and have an axle at the bottom—which all keep them moving at the same time. Some motorcycles have compression damping in one fork tube and rebound in the other—how is that in any way “equal” regarding the left/right fork tube damping adjustments.
If anyone has installed a Race-Tec spring and hears a clicking sound when the forks are compressed it’s because the spring (or washers) are not centered within the fork tube. Just disassemble and realign the parts and the click goes away. Anyone that weighs over 185 and thinks that the stock springs (Gen 1. Don’t know about Gen II) work great does not know how to measure static sag. The stock springs are WAY too soft and screwing the preload adjuster all the way in doesn’t make up for the soft springs.
There, now I feel better...........
Gotta agree with everything just said. :thumbsup:
HaulinAshe
Well-known member
I'm good with everything except the oil viscosity statement. If your fork oil has aged to the point you need to adjust clickers to keep the suspension in the desired performance envelope, CHANGE THE FORK OIL!
3dogs
Well-known member
It's a common practice to "chase" damping adjustments due to oil breakdown (tinning out due to ware) using click adjustments. Racers do this even though they do change their fork oil frequently. AS an example; if 6 clicks out was the ideal damping adjustment for the first race on newley changed oil--after 3 races 4 or 5 clicks may be needed to produce the same damping results. At some point the oil is changed and they start over at 6 clicks.I'm good with everything except the oil viscosity statement. If your fork oil has aged to the point you need to adjust clickers to keep the suspension in the desired performance envelope, CHANGE THE FORK OIL!
charismaticmegafauna
Well-known member
If the above is true, it might be a good idea to send your fork oil off to a lab and have the viscosity checked?
Oil oxidizes, too, during use -- gets thicker (think cooking pudding on top of the stove...). So..., depending on the oil -- there could be either thinning due to shear or oxiditaion due to use.
One way to side-step this is to choose an oil with the highest VI (Viscosity Index) -- the ability to resist change in viscosity.
Oil oxidizes, too, during use -- gets thicker (think cooking pudding on top of the stove...). So..., depending on the oil -- there could be either thinning due to shear or oxiditaion due to use.
One way to side-step this is to choose an oil with the highest VI (Viscosity Index) -- the ability to resist change in viscosity.
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NC Rick
Member
Interesting comment on the fork oil. The highest VI oils tend to be shock oils. In a shock we do not have the same issues with oxidation as in the fork, nor nearly as much water and dirt intrusion. I wonder how the additives that give us the high VI numbers effect the other oil properties.
With regard to setting up suspension by bouncing the bike, please keep in mind that our suspension systems are not quite that basic. Bouncing the bike and finding the critical damping point (just were there is no "overshoot") gives us a good idea where to start for our bleed. It will not account for how the suspension operates at different velocities. The complex shim stacks we have in our bikes make our suspension frequency and velocity reactive (self adjusting if you like...) and the bounce test is only a starting place, not a perfect setup. The compression damping has a big effect on how the suspension works. The rebound damping absorbs (better explained as converting energy to heat) the energy that a bump puts into the spring. The compression damping is there firstly to prevent the spring from over traveling from a given bump but also in a way, to help the spring by converting bump energy to heat before it gets stored in the spring. Naturally these factors are greatly interdependent and working with compression and rebound together allows us as suspension tuners or designers to provide much latitude over ride quality, feel, traction and handling.
With regard to setting up suspension by bouncing the bike, please keep in mind that our suspension systems are not quite that basic. Bouncing the bike and finding the critical damping point (just were there is no "overshoot") gives us a good idea where to start for our bleed. It will not account for how the suspension operates at different velocities. The complex shim stacks we have in our bikes make our suspension frequency and velocity reactive (self adjusting if you like...) and the bounce test is only a starting place, not a perfect setup. The compression damping has a big effect on how the suspension works. The rebound damping absorbs (better explained as converting energy to heat) the energy that a bump puts into the spring. The compression damping is there firstly to prevent the spring from over traveling from a given bump but also in a way, to help the spring by converting bump energy to heat before it gets stored in the spring. Naturally these factors are greatly interdependent and working with compression and rebound together allows us as suspension tuners or designers to provide much latitude over ride quality, feel, traction and handling.
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