Hello, I have started to play w/suspension now. I'm a big believer that my real bang for mod is in this arena so I am slowly studying up and really want to understand this science. So this weekend I was adjusting front preload on my 2003 stock suspended RC51. Current sag was almost 40mm. I wanted to bring it to 25mm. I noticed there are a total of 15 revolutions from soft to hard. I was at 10 revs, took the sag w/me on it, spun it 11, 12 ,13 etc, and the most decrease in sag I got from 10 to 15 (full clockwise to stop) was 1mm?? It seemed like I made a major front fork preload adjustment and nothing happened. Am I doing something wrong? Or are the springs crap.
stock suspension adjusters are designed so that you can't really mess up the bike. the adjustments form one extreme to the other are usually not far out of line of normal adjustments. that's actually really the major advantage of aftermarket suspension parts. the ability to have a much wider adjustment range. it's impressive how far you can f up an aftermarket suspended bike!
You can probably set the adjuster back to the middle, pop off the caps and add a larger spacer (either longer metal or PVC tube or washers) to do a rough increase of the pre-load to get you close to 25mm... then put the cap back on and do a fine adjustment with the adjuster screws. Race tech springs and emulators are going to also help out your front end a bunch. Chad
Thanks. I heard about the spacer thing. Does anybody else have this problem, where stock forks or even rr shock adjustments don't do much to preload? What about ohlins rebuild kits for Rc51? I also found a prob w/the rear shock. Even at lowest setting preload, there is 0 freesag. Tech books say shoot for 5-10mm under it's own weight.
Please include your weight in this scenario? If you are over 150 lbs, the springs are probably to weak anyways.
"I also found a prob w/the rear shock. Even at lowest setting preload, there is 0 freesag" I am not familiar with RC51s, but if you are getting 0 free sag at the softest spring setting stuff I would check: make sure the suspension is not binding. the comp damper screw is not turned all the way in if you are trying to set it in really cold temps it may do this
I will check the items you suggested w/the rear shock. It seems weird, bec all my bikes, (848, cbr600rr, rc51) have 0 free sag. I'll set the bike on the ground, give it a few pumps on the tail, and when I lift on the tail it is already full high position. Weird. And on the cbr, it was full soft on the rear shock! Maybe springs are too hard from factory? Btw I am 180 lbs.
Make sure that you are pressing down hard and then letting up easy to measure free sag... there is stiction that may be causing the shock to stick at the top. Also remember how small 5mm is!! I am sure there are more, but here are a couple of articles I found with a quick search: http://www.ehow.com/how_4602262_setup-suspension-sportbike-motorcycle.html http://www.ntnoa.org/suspension_preload.htm Chad
Not to suggest you are doing it wrong, but ensure you are turning the adjuster for preload and not the adjuster for comp/reb damping. Just a thought as I would have guesed more than 1mm of reduction from your noted adjustment. 1mm is not easily measured accurately when it comes to sag, that sounds like no change to me.
I'm kind of surprised that no one has said anything yet, but 25mm of front sag (loaded with gear on) is NOT a lot. Normally, most suspension guys shoot for 30 to 38mm of sag on the front and around 25-28mm of loaded sag on the rear. On the front forks you are shooting for approx. 1/3 of the fork travel when loaded with gear. Assume a front fork travel of 4.3 to 4.5 inches of travel. Divide that by 3 and you get.... 1.43 to 1.5 inches of travel, which equates to.... 36.3mm to 38mm.
Thanks for all of the input. We worked on the sag this weekend, and could not get any less than 37 in the front. The front preload could turn a full 16 revolutions from hard to soft. After the 10th turn, 10-16 had no effect to reduce front preload. ?? Weak spring is my only thought. On the rear, we adjusted preload to setting #3 soft from 1-10 hard. I think we got about 35mm and at least 5mm static. It's weird, the bike feels like a cadillac now. I'm worried about this because it has so much squat but we'll see this Sunday at TGPR. Huh. Maybe it's time for Ohlins?
I still think that most peeps are in the 25 - 30mm on rear sag when loaded and with gear on. Personally, I stay closer to the 25mm setting. Front, as I stated before needs to be in the 35 -38mm range and personally, I'm at 36mm on the front. I've got a new Ohlins TTX coming tomorrow for my 600RR and when it gets installed tomorrow evening, I will be at 25 - 26mm loaded sag with it also. The good news for this weekend is........Tally is a fairly smooth track and shouldn't "test" your suspension nearly as much as if the next trackday was at ........say.........Nashville!!!