Author Topic: Compression and Rebound...  (Read 8039 times)

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teamgreen500

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Compression and Rebound...
« on: April 20, 2004, 04:15:55 PM »
This is a "Riding Tip", trust me on this!

I've recently been teaching my friend's kid how to ride. When he and I were discussing the suspension settings on his kid's bike I realized that he wasn't real familiar with what I was saying. I also realized that most of the folks I know don't fiddle with their "Compression' and "Rebound".

Compression: The shock or fork valving feature that controls how fast or slow the shock or fork compresses. Now think about that for a minute. How "fast" or "slow" really means how well the fork or shock absorbs a bump/hit. If it absorbs the hit to quickly it will bottom..."Klank"! If it absorbs the hit too slowly it won't "travel" upward enough and you'll, also, feel the hit; however, it's a bit better than the "Klank" of a real bad "Bottom-out"! :shock:

As for "Rebound"? Well, I'm gonna wait for Rick to check in on that one...he's got a little extra time as of late :cry:

Manny

Rick

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Compression and Rebound...
« Reply #1 on: April 21, 2004, 09:11:59 AM »
Thanks, Manny.  You know how hard it is to type those lengthly responses with one hand?? :wink:

Compression: A lot of folks think that the less the compression dampening the better.  Manny delt with this, so avoid the clunk.  Work to find the balance.

Shock Rebound:  Shock rebound is hard to set, as rebound that is too slow can cause "packing", making the rebound feel too fast.  With packing, your shock is rebounding so slow that it does not have time to rebound fully before you hit the next bump.  The result is that it "feels like" you shock is rebounding too fast.  Most folks will turn the rebound adjustment screw in a few more clicks, making the packing even worse.  If it feels as though you have too much rebound, or like the shock is kicking you in the rear, it is a good idea to turn the srew out as an initial test to see if your shock is packing (keep notes, with comments, as you might find the best ride early, but then not remember what it was by the end of the day).  If you are starting fresh, start with the adjustment screw in the middle and work out or in.  My shocks (stock and revalved by ACME) usually settle in at around 10 clicks out from full in, but I hate too much rebound because I ride so far over the bars.  Also, when turning the adjustment screw in all the way, be careful not to bottom the screw too hard against the seat, as you will distort the seat.  It takes some practice to dial in a shock, but just practice.  Use an experienced rider to help by watching you hit the whoops or jumps.  Your freind will be able to watch the bikes balance as you pound the whoops, with invaluable input.  

Fork Rebound:  Fork rebound is much less critical than shock rebound, but a well tuned fork can mean the difference between suspension that works pretty good, and suspension that works great.  In general, forks that rebound too slow will rob you of the initial dampening characteristics of your compression circuit because the forks never have a chance to return to full extension.  (As a note, I run my rebound faster for woods riding and slower for desert and high speed riding.  In the woods, you rarely bottom the forks, and want to be able to get around the turns at every tree.  Keeping the forks fully extended helps keep the weight balanced between the front and back.)  Start your adjustments by setting the rebound screw in the middle, and work the compression adjustment first.  Once compression is pretty close, turn the rebound screw in or out (does not matter at first) three turns.  Ask yourself if the result is better or worse.  If rebound is too fast, you will deflect rather easily, so turn it back to center and then three turns out.  Too slow, and you lose some suspension travel.  This is essentially trial and error.  As a general rule, my fork rebound will be plus or minus no more than three clicks from center.  Just remember, as you change fork compression, you will have to change rebound.

Finally, don't try and perform initial suspension testing by just going on a ride.  Instead, find a section of trail with turns, whoops, jumps, etc. and ride it until you are comfortable, then begin to change suspension settings.  Fine tuning can be done later, but initial tuning should be done a the same section over and over and over and over...

If you are having a tough time setting rebound, post up your questions and we'll try and make things work out.

Good luck.

Rick

kawdude

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Compression and Rebound...
« Reply #2 on: April 21, 2004, 10:16:31 AM »
How does rider weight effect these settings?

teamgreen500

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Compression and Rebound...
« Reply #3 on: April 21, 2004, 10:35:55 AM »
Believe it or not "Rider Weight" is, for the most part, a "Spring and Sag" thing. You're "Valving" settings are really about your preferences and riding style.

I'm very partial to a firm yet compliant set-up. Kinda Moto-X goes Desert Racing, if you will.

I CAN-NOT stand a bike that runs around with 1/2 of it's travel gone while in the parking lot AND I REALLY can't do with "Soft" rebound! It really chap's my A...

Here's a hint...

The "Lighter" you are, the more important the rebound (Especially in the rear...) is. It's a Catapult thing!

Manny

Rick

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Compression and Rebound...
« Reply #4 on: April 22, 2004, 04:46:59 AM »
As an additional note, as you improve your riding position to be more over the bars, you will have to readjust your rear shock, as the weight distibution will change.  

Boy that rear shock is just loads of fun....

Rick

Offline hughes

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Compression and Rebound...
« Reply #5 on: December 21, 2004, 05:52:40 AM »
Quote from: Rick
Thanks, Manny.  You know how hard it is to type those lengthly responses with one hand?? :wink:

Compression: A lot of folks think that the less the compression dampening the better.  Manny delt with this, so avoid the clunk.  Work to find the balance.

Shock Rebound:  Shock rebound is hard to set, as rebound that is too slow can cause "packing", making the rebound feel too fast.  With packing, your shock is rebounding so slow that it does not have time to rebound fully before you hit the next bump.  The result is that it "feels like" you shock is rebounding too fast.  Most folks will turn the rebound adjustment screw in a few more clicks, making the packing even worse.  If it feels as though you have too much rebound, or like the shock is kicking you in the rear, it is a good idea to turn the srew out as an initial test to see if your shock is packing (keep notes, with comments, as you might find the best ride early, but then not remember what it was by the end of the day).  If you are starting fresh, start with the adjustment screw in the middle and work out or in.  My shocks (stock and revalved by ACME) usually settle in at around 10 clicks out from full in, but I hate too much rebound because I ride so far over the bars.  Also, when turning the adjustment screw in all the way, be careful not to bottom the screw too hard against the seat, as you will distort the seat.  It takes some practice to dial in a shock, but just practice.  Use an experienced rider to help by watching you hit the whoops or jumps.  Your freind will be able to watch the bikes balance as you pound the whoops, with invaluable input.  

Fork Rebound:  Fork rebound is much less critical than shock rebound, but a well tuned fork can mean the difference between suspension that works pretty good, and suspension that works great.  In general, forks that rebound too slow will rob you of the initial dampening characteristics of your compression circuit because the forks never have a chance to return to full extension.  (As a note, I run my rebound faster for woods riding and slower for desert and high speed riding.  In the woods, you rarely bottom the forks, and want to be able to get around the turns at every tree.  Keeping the forks fully extended helps keep the weight balanced between the front and back.)  Start your adjustments by setting the rebound screw in the middle, and work the compression adjustment first.  Once compression is pretty close, turn the rebound screw in or out (does not matter at first) three turns.  Ask yourself if the result is better or worse.  If rebound is too fast, you will deflect rather easily, so turn it back to center and then three turns out.  Too slow, and you lose some suspension travel.  This is essentially trial and error.  As a general rule, my fork rebound will be plus or minus no more than three clicks from center.  Just remember, as you change fork compression, you will have to change rebound.

Finally, don't try and perform initial suspension testing by just going on a ride.  Instead, find a section of trail with turns, whoops, jumps, etc. and ride it until you are comfortable, then begin to change suspension settings.  Fine tuning can be done later, but initial tuning should be done a the same section over and over and over and over...

If you are having a tough time setting rebound, post up your questions and we'll try and make things work out.

Good luck.

Rick
Rick, Good explames of compression and rebound. My 87 kx500 has damping rod style forks with compression adjustments only. Is my rebound controled by oil wt. only or does the cylinder valve in the lower fork leg change compression and rebound all in one valve :?: I'll understand if you are not experniced with these older forks. It's hard to find any theory on the operation of these forks.Thanks
Open Class 2-Stroke Kawasaki KX500
Yamaha 2005 YZ250
Richard Hughes
Dirt Hammers - Online Off-Road Journal
hughes@dirthammers.com
http://www.dirthammers.com

Rick

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Compression and Rebound...
« Reply #6 on: December 23, 2004, 02:28:54 AM »
Unfortunately, the only bikes I have tuned that are missing the rebound controls are the early 80cc bikes my oldest rode when we first started.  In this case, Matt wasn't going fast enough to worry about rebound control, so I only focused on compression.  Sorry I could not be more help.

Rick

Offline hughes

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Compression and Rebound...
« Reply #7 on: December 23, 2004, 07:32:20 AM »
Thanks for the reply,

If you run across any info or theroy on these 87 model damping rod forks please pass it along. Thanks.
Open Class 2-Stroke Kawasaki KX500
Yamaha 2005 YZ250
Richard Hughes
Dirt Hammers - Online Off-Road Journal
hughes@dirthammers.com
http://www.dirthammers.com

Rowdy-Yates

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Compression and Rebound...
« Reply #8 on: January 08, 2005, 06:51:58 AM »
Rick come over and help me set up my suspension! HEHEHE

Rick

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Compression and Rebound...
« Reply #9 on: January 24, 2005, 02:55:51 AM »
Heck, if I had my way, I would just travel around working on 500's, but doubt I could make enough to pay the bills....