Rear shock preload - Glenn has it figured out

[Eric K]

I read what Glenn (GMP) observed about rear spring preload and suspension behavior.

I reduced my preload from about 12 mm to 10mm, which changed the loaded sag from about 125mm to 130mm. As a note, I mainly ride woods, I weigh 270 geared up and run a 5.6 spring. I felt a big difference in the smoothness of the rear suspension over the sharp edged step ups. The rear used to kick noticeably on the square edged, step up bumps with the 12mm preload that couldn’t be fixed with clicker adjustments. Now it is way smoother, with no noticeable kick over the sharp step ups. It still turns sharp. I could not feel a difference in the steering. I am thinking that preload and free sag are far more important than loaded sag in proper set up.

[GMP]

Eric,

Don't thank me, pobit suggested this first. Credit where credit is due. I just verified it with additional testing on my '07. We even applied this method to my brothers Husky WR 250 with good results.

Glad it worked out. The preload is more important, because it affects the initial travel, and rebound before the suspension tops out. Whats amazing, and that people find tough to beleive at first, is that the bike still steers great at over 110 mm sag. You should now be able to use the comp clicker to fine tune the ride and end up in the middle of the range, not near the full out position. I can run at race speed (B class) in the rocky stuff with confidence. A firm, controlled, but non-abusive ride. LTR valved Sachs, 5.2 spring @ 9mm preload.

I'll bet the forks feel better too.

[PEB]

I am a bit embarrased to admit I finally got around to setting the static sag on my bike. Before I monkeyed with it it was set to nearly 60mm(no preload at all. I set it to 30mm and gave it a test ride. Huge difference, the rear end semms much more active now, the bike used to feel like it had a flat all the time. I may increase the compression dampining a little next time out. The front end felt very twitchy which should be solved by dropping the tubes in the clamps. I am also planning on taking my sag scale(string and some tape) riding with me to have a friend measure the sag with me on the bike. You guys talk about 10-12mm preload, is that on the shock body or is that measured static sag.

Paul B

Thanks for the info, this board rocks!

[GMP]

I'm refering to actual shock spring preload, not sag. With the bike on the stand spin the ring back out until there is no preload, take a measurement, and turn it back in 8mm for starters.

[PEB]

Does that spec vary year to year? I am pretty sure my 02 has a shorter shock than most.

Paul B

[GMP]

Its not actually a spec, just something that was derived experimentally. The '02+ shocks are the same I beleive.

[PEB]

How much static sag does this produce? More or less than the 30mm I see recomended?


Paul B

[GMP]

Paul,

It depends on your weight and spring, but generally more. Forget about the sag numbers for now. Read the posts on this subject and try it. Spend a couple hours on the same section of trail for consistancy. The race sag may end up over 115mm but thats OK as long as the bike steers. This will unload the fork and make it eaiser to tune as well. On my bike, everything seemed to come together in balance better.

[Eric K]

The key is to adjust your suspension based on how it performs and how the motorcycle handles. Don't get hung up on the numerical sag specs.

[KTMLew]

Originally Posted by Eric K

The key is to adjust your suspension based on how it performs and how the motorcycle handles. Don't get hung up on the numerical sag specs.

I hope Vinduro doesn't see this as he will flip out...