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Kevin Duke
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   Posted 6/16/2005 10:30 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
There are a lot of myths and misconceptions about setting up a suspension. Whether a fork or a shock, a suspension operates dynamically on three basic levels.
 
1. Spring: It has a certain tension built in, and can be made more resistant to using its stroke by compressing the spring in what is called adding preload. Preload can only compensate for so much. Riders who weigh more than 200 lbs and less than 120 lbs will probably be best served by getting a harder or softer spring(s).
 
2. Compression Damping: It limits how fast the suspension compresses. Adding compression damping results in making the oil circuits inside the suspension components smaller, allowing less oil to pass through and making the suspension stiffer.
 
3. Rebound damping: It slows the rate at which the suspension "rebounds" after hitting a bump, using oil circuits similar to the compression damping.
 
Most modern sportbikes have these three adjustments built in, but bikes built with lesser performance might not have any. Mid-line stuff might have just rebound damping and/or preload adjustments.
 
It's a common sight to see riders adjusting their compression or rebound damping "clickers" without setting their suspension's "sag." Sag is the amount the bike compresses from fully extended, with the rider on board. A hard and fast rule is that you should set your sag for your weight before you even think about messing with the damping adjustments.
 
IMO, the best way to adjust sag is by Race-Tech's method (http://www.race-tech.com/), which I've copied and pasted below.
 

 

  1. First extend the forks or shock completely and measure from the wiper to the bottom of the triple clamp on forks or from the axle to a vertical reference point on the chassis. This is L1.
  2. Take the bike off the stand, put the rider on board in riding position. Get an assistant to balance the bike or have the rider hold onto something, comress the suspension about 25 mm (1") and let it extend very slowly (slowly is the critical term). Where it stops, measure the distance between the wiper and the bottom of the triple clamp or the axle and the reference point on the chassis again. Do not bounce. This is L2. (If there were no friction in the seals the bike would come up a little further.)
  3. Next lift up on the suspension and let it drop very slowly. Where it stops measure again. Do not bounce. This is L3. The reason L2 and L3 are different is due to stiction or drag in the seals and bushings. (If there were no friction in the seals or the linkage the bike would drop a little further.)
  4. Half way between L1 and L2 is where it would come to rest with no friction. Therefore L2 and L3 must be averaged and subtracted from L1 to calculate true Static Sag.
    Static Sag = L1 - (L3 + L2)/2
  5. To adjust Static Sag make longer or shorter preload spacers or use the preload adjusters, if available.
    It is important to note that there are no magic Sag numbers. However here are some guidelines to use as starting points.

Bike Type Front % Front mm Rear % Rear mm Rear Free Sag mm
Off-Road Bikes 22-25% 65-75mm 30-33% 95-100mm 15-25mm
Off-Road 80cc Mini's 22-25% 55-65mm 30-33% 75-80mm 10-20mm
Street Bikes 28-33% 30-35mm 28-33% 30-35mm 0-5mm
Road Race Bikes 23-27% 25-30mm 23-27% 25-30mm 0-5mm

I hope that helps. Now, all of you go set up your suspension!

 


-KD, MCUSA Editor

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Kevin Duke
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   Posted 6/16/2005 12:13 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
When I get a new test bike, after setting the sag I usually start backing off the damping clickers for max comfort (I'm getting old...). Then, once things start getting too "loose" I'll start adding compression and/or rebound as required. What I end up with won't be so hot on the track or when really attacking a deserted back road, but it's optimal for the 95% of my other normal riding duties.


-KD, MCUSA Editor

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RedDog
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   Posted 6/16/2005 7:40 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Excellent! Need more of this.


RedDog
Travel Light & Leave Your Fears Behind You!
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Kevin Duke
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   Posted 6/16/2005 8:05 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
I need more time in a day!


-KD, MCUSA Editor

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Hiputong Stekward
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   Posted 6/16/2005 8:07 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
  The bike you say is the motorcycle? 
   what's the mean:    after setting the sag ?
hiputong  Stekward


Motorcycle is the most favourite for young!  email : hiputong@hotmail.com    MSN: hiputong@hotmail.com
 
 

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CaddmannQ
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   Posted 6/20/2005 10:38 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
It means adjusting the springs to compensate for the weight of the rider.


Cadd
2004 Nomad 1500
VROC #11619 Rolling Blunder #128

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bunchof6
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   Posted 6/22/2005 12:02 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
Hey, I found a guide that may help visualize what Kevin said, a bit. Being a visual thinker, it helps me.

Click




Elemental Science Project

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RedDog
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   Posted 6/22/2005 8:10 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Good one. Let's attack some of the more complicated issues regarding motorcycling - it's so important for your ride.


RedDog
Travel Light & Leave Your Fears Behind You!
Normal People Scare me!

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Kevin Duke
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   Posted 6/23/2005 10:13 AM (GMT -7)    Quote This PostAlert An Admin About This Post.

A couple more notes about damping adjustments.

On a fork, rebound damping is almost always at the top of its legs, while compression is somewhere near the fork leg's bottom. On most shocks, the compression adjuster is on the remote reservoir; rebound is usually a screw near the shock's bottom.

Your suspension tuning will be more successful if you log where they're set. From your starting postion, screw in the adjusters and count how many clicks/turns it takes to bottom out. That's how many clicks/turns out they were set from maximum. Then, as you make adjustments, keep logging where the clickers are set. Also, make sure the fork's compression and rebound adjusters are syncronized to the same clicker positions in each leg.

Getting rebound damping in the right ballpark can be done without riding the bike. For example, the rear shock's rebound can be tested by holding the bike by its tailsection or rear seat and giving it a quick shove downward. What you don't want to see is the rear end quickly bounce back up to its topped-out position (too little rebound damping) or rise too slowly (too much damping).

If it rises too slowly, the suspension won't recover its full travel in time to hit the next bump, resulting in what's called a "packing" condition. To check front rebound damping, bounce the front end downward with the bike's handlebars and adjust the clickers in the manner described above for the rear shock.

This procedure will get the rebound damping dialed in close to optimal, although the true test is how it works on the road, and your set-up might require further tweaking.

Keep in mind that the adjustable damping circuits for both compression and rebound are variable only in the lower-velocity range. Excessive high-speed (sharp-edged bumps) compression damping (causing harsh suspension reactions) can only be subtly reduced by the damping adjusters.

*Final Note* Don't bother making damping adjustments until you've set your spring preload according to the aforementioned sag procedure!


-KD, MCUSA Editor

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RedDog
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   Posted 6/27/2005 10:23 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
We're going now - I like it.

A track racer took my bike for a spin in the Ozark Mountains this weekend - just for the Halibut cause I do not lend my bike out to everyone. Besides smiling the helmet off when he arrived, after I anxiously had expecting him back a little earlier than 58 minutes, he stated: This is too stiff but awesome, way too stiff in the rear, but I understand you ride 2Up.

He weighs 190 and we don't. I am happy with that.

More please ...


RedDog
Travel Light & Leave Your Fears Behind You!
Normal People Scare me!

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Kevin Duke
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   Posted 6/28/2005 9:31 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
Expect more, Red, including a report on a suspension seminar I attended with noted motorcycle engineer Tony Foale. Now if all these cool new bikes would quit arriving in our garage, I might actually have time to write about it!


-KD, MCUSA Editor

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RedDog
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   Posted 6/28/2005 10:09 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
That's is not a problem! It's a challenge! And one solution is to send some of them this way. Hear me now?


RedDog
Travel Light & Leave Your Fears Behind You!
Normal People Scare me!

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Kevin Duke
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   Posted 6/28/2005 3:33 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Or, if it is a problem, it's one I choose! When I figure out how to stuff a bike into one of those FedEx envelopes, I'll send one your way!


-KD, MCUSA Editor

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1Hawk
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   Posted 9/5/2005 12:29 PM (GMT -7)    Quote This PostAlert An Admin About This Post.

Most of the bikes I have read about are set up for riders that weigh 180 pounds.  I weigh 180 with my gear on and this includes the helmet.  I adjusted the Harley up in the rear as I often ride 2up so it's a bit stiff when I am solo.  The FZ6 is at the factory settings and I love it......

 

Hawk


 

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Smax
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   Posted 9/13/2005 1:40 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
Kevin, thanks for the tech article (missed it before), keep 'em coming!

1Hawk: huh?


quiet GSX-R 1100, midrange monster...

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bgdsteve15
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   Posted 9/23/2005 9:10 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Excellent thread, most people will put up with a very ill-handling bike because they don't know anything about how they should ride.
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louemc
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   Posted 9/23/2005 9:53 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
At the risk of saying something that is either obvious or totally inappropriate, to get the most accurate (not false measurements from stiction) for the sag measurment, I get the unloaded point, with the wheels off the ground. Any thoughts on that? Kevin?  RoK ON ?
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Kevin Duke
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   Posted 9/23/2005 10:06 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Lou, I agree with you about getting the wheels off the ground, and I'd hoped that would be obvious by Step 1 in Race Tech's procedure. Thanks for your reliable input.


-KD, MCUSA Editor

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louemc
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   Posted 9/23/2005 10:22 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Okey Dokey, Thingy is, I've seen several picture articles that say full extension, and they have the bike on the ground, and pull up on the rear fender or handle bars, and call that full extension, and as often as not, the bike sets back down or not, or a random amount, depending on stiction, and I just wanted to have it pointed out super clear in case someone wasn't sure.
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