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]

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...

 

[GMP]

He's such an open minded fellow isn't he?

 

[KTMLew]

He's such an open minded fellow isn't he?

I'm sure he would say something about "doing it the right way" instead of doing what works? He would have all of you using 7.0 springs...across the board, weight is NOT a factor...

 

[iancp5]

I'm sure he would say something about "doing it the right way" instead of doing what works? He would have all of you using 7.0 springs...across the board, weight is NOT a factor...

I think you're being a little harsh. On my KTM I told him my weight and terrain and he told me a setting that worked pretty well. It was suggested as a starting point not a must have.

 

[Brian VT]

I saw these preload bearings at Factory Connection. I don't know if they're available for Ohlins or Sachs. Do they seem like a good idea to you guys ? They claim that reducing the torsional binding of the spring is the benefit. Makes sense to me but kinda spendy ($110).

 

[GMP]

I'm sure it will make spinning the preload ring easier when new and clean/lubed, but after its packed with dirt I doubt it. The threads on the shock body/ring are also important. IMO, gimmick. Just clean the shock good, WD40, and it spins easy enough with the weight off the wheel. Once the preload is set to your liking you don't touch it anyway, just take an exact measurement and reset it there for the next time you have the shock out for service.

 

[KTMLew]

Factory Connection sure likes to make a good mark-up!

http://cgi.ebay.com/ebaymotors/ws/e...m=230159711091&ssPageName=STRK:MEWA:IT&ih=013

 

[skid jackson]

The FC bearing has the fancy billet cap that threads onto the shock body
I actually know a little bit about the developement of the FC one. They evidently had a shock on a shock dyno and decided to film it with a high speed camera. Results showed the spring binding and "catching" on the upper adjuster ring as the shock went through its stroke. The bearing got rid of the friction and evidently allows the spring to work better, resulting in a smoother stroke!!! ... may sound like a load of crap but ... seems plausible. Besides fc did the suspension on my drz and it kicked butt!! it is spendy but if I was on the z i might get one as an xmas gift for the bike

 

[GMP]

If thats the case, I would think it would be a function of the individual shock (brand) preload ring design, as far as the OD/length of the pilot section vs. the ID of the spring is concerned. I think this is a stretch, and would have been addressed a long time ago if it were a general problem. A steel spring covererd with dirt would make quick work of an aluminum preload ring during regular contact and it would be obvious at the next shock service, don't you think?

For $20 the bearing might be handy for setting up a new bike / clean shock especially for adjustments in the woods. I still think it will be useless after the elements take over though.

 

[KTMLew]

If thats the case, I would think it would be a function of the individual shock (brand) preload ring design, as far as the OD/length of the pilot section vs. the ID of the spring is concerned. I think this is a stretch, and would have been addressed a long time ago if it were a general problem. A steel spring covererd with dirt would make quick work of an aluminum preload ring during regular contact and it would be obvious at the next shock service, don't you think?

For $20 the bearing might be handy for setting up a new bike / clean shock especially for adjustments in the woods. I still think it will be useless after the elements take over though.

I think the one I linked is for street/road-race bikes actually. It would have to be better sealed or disassembled after every ride for our use though.

 

[Ryno]

FACTORY--every race they clean and lube this little part and I'm sure has some effect on binding but us mear mortals have a long way to go until we could say it had an effect for us. Factory guys Yes!