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Enduro Suspension Tuning & maintenance of Enduro forks, shocks, etc |
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#1
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Rear shock preload - Glenn has it figured out
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.
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Eric K '06 GasGas EC300 '01 GasGas XC300 |
#2
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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. |
#3
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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! |
#4
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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.
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#5
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Does that spec vary year to year? I am pretty sure my 02 has a shorter shock than most.
Paul B |
#6
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Its not actually a spec, just something that was derived experimentally. The '02+ shocks are the same I beleive.
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#7
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Quote:
Can you post the step-by-step procedure on how to do this. Thanks. |
#8
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Pretty easy stuff. The preload is the amount you compress the spring with the adjusting nut/ring. Support the weight of the bike on a stand and back the nut off until it just touches the spring to have zero preload. From that point the more you compress the spring the more preload you have, measured in mm's.
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jeff '00 XC250 (mine) LTS front and rear suspension, power valve cover, carb jet kit and rear chain glide, RB Designs head mod, BRP tall triple clamp, backyard foot-peg lowering conversion. '04 EC250 (the kids) (he can do his own mods haha!) |
#9
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I have my sag set at 100mm.
I'm just wondering about the 125-130mm sag. Wouldn't that "rake" the front end out too much? |
#10
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i have the same question - i just set my preload at 10mm, and i get 120mm of sag.. i normally would run around 105-110mm. will 11mm or 12mm of preload get me to 110 and still not sacrifice rebound etc? it's too cold to go out and run it, but i would think 120 would sacrifice turning ability... i've got a 5.4 spring, ltr lowering link, and 195lbs with full gear. also my static sag is 55mm... seems strange to me (i would assume it would be closer to 35mm... ) - does the lowering link affect static sag that much (i would assume it changes the leverage)?
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