My fork rebound-valving is wrong, have too much rebound w/ the adjusters all the way out....packs up on bumps.
They also have too soft springs for my weight....bottoming out to the stops under braking.
Bike bottoms out and packs/locks up and (skips) on bumps.
Dont have time to ship them to suspension guy yet.
If I add 5cc of Ohlins fork oil, increasing my oil volume and thus decreasing the tendancy to bottom out....will my rebound be affected by it, meaning will it get even worse? The last thing I want is more rebound!!!! :ahhh:
I know compression will be affected, but what about rebound???
I dont think it would, but I want to make sure B4 I add the oil.
Thanks!!!!!
Well, if you know you have too soft springs, replace them.
What's your sag at?
Adding oil isn't going to reduce your rebound dampening unless you add so much that the fork doesn't function.
Dampening shouldn't overcome the spring. Sounds like the forks have issues, and you've known about it for a while. When are you planning on fixing the rest of the bike after you crash? Seriously, if you've got that much rebound, you're just looking to throw it all on the ground, Eric. Get it fixed so that you're not wasting your time and money on track.
SUPER Dave!!!! 8) I was hoping you woould have advice in this thread
Quote from: Super Dave on May 10, 2010, 05:44:38 AM
Well, if you know you have too soft springs, replace them.
I can't get the forks shipped til the following Monday after the MCRA trackday. The forks were already rebuilt and the right springs/valving were supposed to be in there. I always just figured they were...I knew nothing of suspension.
Quote from: Super Dave on May 10, 2010, 05:44:38 AM
What's your sag at?
GSXR1000 2005.
Rider sag at 30mm front. 4 lines of preload showing. Rebound all of the way out. Compression 6-out (19 or 20 click range)
The forks bottom so hard the zip-tie leaves indentions in the fork's dust-seal.
Don't know if it is bottoming on brakes or bumps, or both.
Bike feels great on the brakes, rear-end is a little light, moves around a little under super hard braking.
Bike packs up on the first bump (feels like it has run out of travel, and the rebound isn't letting it back out). Just hits, bottoms, and then skips across the bumps.
With the rebound adjusters all the way out, the forks visibly return too slowly, just manually pumping the forks.
I honestly never really thought anything was wrong.
I had the forks/valving done by one of the best, believed it to be dead nutz correct. Had it adjusted and tweaked by a knowledgable racer to were it felt really good everywhere except on the bumps. Geometry wise the bike is dynamite!
I figured the problems over the bumps was me tightening up and clenching the bars, inducing it. Always felt like if I was more relaxed over the bumps the bike would be fine.
I finally tried that at Putnam a couple weeks ago, stayed light/relaxed on the bars and carried my speed over the bumps. Instantly packed up and chattered. I stayed relaxed and kept doing it, and the same result. Went faster, same result.
I asked guys that were going the same pace as me if they were chattering in T2 and T9, and they said they couldn't feel any bumps.
Right then I knew something was wrong. My zip tie was also at the bottom.
I went to Jay Q and he showed me correct rebound action on his forks, and mine is way slower in comparison, and I don't have any adjustment left. It takes about .5-.7 second for my forks to re-extend.
Then I checked the rider sag and I was at 30mm. I believe I am supposed to be at 35. I am sure my tuner friend cranked them down due to seeing his ziptie getting crunched when I would pit. I didn't know anything about suspension, all I knew was he made the bike a lot better, even in the bumps. I figured my ass-clinching in the bumps was mental...I just foound out it's not :wah:
I figured if I could keep the sag at 30mm, add some oil to keep it from bottoming, it would help some. Also thought I could remove some of the Ohlins 15wt and replace it (and add 5cc) with 7 weight, it would dilute the oil to a lighter vicosity and reduce the excessive rebound.
Was also thinking of adding 1-2 pounds of air in my front Mich to aid in faster rebounding (of the tire at least).
I know this is all a bandaid, but no time to ship out forks till after GIR. I blame this on me for not learning about suspension sooner so I could have caught the problem...NOT the guy who tuned them.
Now crush my GIR dreams :biggrin:
Any advice you can offer Dave, is super appreciated!!! :cheers:
Speedy, This is Randy. You could try a 5 or 7 weight oil as a band aid. to help the rebound return a bit quicker (thinner oil flows easier through the valve ports),and the dive on the brakes will be a product of the compression valving not set high enough which the lighter oil may help a bit. Adding fork oil will help slightly with the dive by reducing the "air spring" space, and not affect the dampening as long as you don't add so much as to hydrolic lock the forks. but it is all just a bandaid, Like dave said you need to get the forks fixed asap! Oh and Long live Jojo bitts!!!!!
Quote from: duckracer996 on May 10, 2010, 11:41:02 AM
Speedy, This is Randy. You could try a 5 or 7 weight oil as a band aid. to help the rebound return a bit quicker (thinner oil flows easier through the valve ports),and the dive on the brakes will be a product of the compression valving not set high enough which the lighter oil may help a bit. Adding fork oil will help slightly with the dive by reducing the "air spring" space, and not affect the dampening as long as you don't add so much as to hydrolic lock the forks. but it is all just a bandaid, Like dave said you need to get the forks fixed asap!
Hi Randy, That is exactly what I thought and was hoping to get confirmed.
Do you think 5cc would be safe? sufficient??
Forks are going back Monday after GIR :)
JoJo Bits Rocks!!! ....stickin' it to da Man! :biggrin:
(https://www.ccsforum.com/proxy.php?request=http%3A%2F%2Fimg.photobucket.com%2Falbums%2Fv405%2FSpeedballer%2Fjojooink.jpg&hash=ef6f20b3b86ffea9055421296925486dfb50d2df)
Some food for thought....
Bottomed out suspension will definately cause the bike to skip over bumps, the damping at that point is not able to do its job very well (if at all). If the springs are too weak for your situation then damping changes may only help minimally.
Comparing 'free' and 'rider' SAG numbers basically identifies if you have the correct springs for your application, then if you do have the correct springs it allows you to make some tweeks to your set-up by adjusting pre-load. If the springs are wrong for your weight then you can more or less throw preferred SAG numbers for your application out the window and go to 'damage control' with what you have. Adding more preload to your springs (if their too soft) will mess up your SAG numbers, but it will also help to slow down your springs compression rate. In my opinion you need to get more spring into your situation to help stop the bottoming out situation in the 1st place, with the springs you have currently the easiest way to get that is more pre-load. Of course that's a compromise and may cause other handling issues because your suspension will have more initial spring pressure, but it may be better than what your dealing with currently.
I also wonder if you need a little more compression damping to help stop the suspension from bottoming in this situation, if that helps the suspension from bottoming out it should be better than what you have now.
Good luck! :thumb:
only had a minute and there already is a good deal of info posted already. May already be indicated, but as Dave indicated a bit more fork oil won't affect damping. Since fork oil LEVEL only affects the lower portion of travel, that is how you keep forks from bottoming provided your sag #'s are correct. In other words, if you have the right springs but are bottoming, adding a bit more fork oil will keep from bottoming. Goes without saying though, too much oil will hydro lock the forks and they won't work right.
I normally run 190mm from the top, but at VIR due to the long front st-8 braking area, i run another 10mm of oil. No other track i do has a braking area that is so long from such a high speed.
How does the rear feel?
Quote from: Gixxerblade on May 10, 2010, 07:09:09 PM
How does the rear feel?
Speedy's not that kind of guy!
Quote from: Burt Munro on May 10, 2010, 07:50:13 PMSpeedy's not that kind of guy!
I don't even want to know how you acquired that information! :ass:
Quote from: Burt Munro on May 10, 2010, 07:50:13 PM
Speedy's not that kind of guy!
LOL!!!!!!!!!
Rear is same as front, perfectly balanced front and rear. Rear has infinite amount of adjustment so no issues getting it correct, or balanced to a changed front-end.
Thanks everyone for all of the information, advices and help!!!!!!!
I am going to leave my front rider sag at 30. With the springs so weak, it still offers a plush ride. If I went to (correct) 35 it would bottom even worse.
I'll add 5cc per leg of 5wt fork oil, to keep the front end from bottoming and hopefully to dilute the fork oil so my rebound decreases a bit.
Thanks again everyone! :-)
Quote from: MELK-MAN on May 10, 2010, 01:11:51 PM
Since fork oil LEVEL only affects the lower portion of travel, that is how you keep forks from bottoming provided your sag #'s are correct. In other words, if you have the right springs but are bottoming, adding a bit more fork oil will keep from bottoming. Goes without saying though, too much oil will hydro lock the forks and they won't work right.
You know, I am wondering.....
The fork springs were supposed to have been fitted to my weight. If you pump my forks they feel stiff! On the track they feel fine, don't seem to dive excessively. The ziptie and bumps are the only thing letting me know they are bottoming.
But they feel stiff pushing on them. It's like all of the issues are at the very bottom of the travel.
Is is possible when my forks were done, they put an incorrect amoount of oil in them (too little) and now they are bottoming because of the big air gap/volume? ....Not because of too little spring rate.
Again, the springs feel stiff pushing on them. Other than on bumps the handling/geometry seems perfect.
Does anyone know the correct oil level for an 05/06 GSXR1000.
Maybe the forks just have too little and too thick oil?
loose weight, that should fix it
Quote from: Speedballer347 on May 10, 2010, 10:23:35 AM
GSXR1000 2005.
Rider sag at 30mm front. 4 lines of preload showing. Rebound all of the way out. Compression 6-out (19 or 20 click range)
The forks bottom so hard the zip-tie leaves indentions in the fork's dust-seal.
Don't know if it is bottoming on brakes or bumps, or both.
Bike feels great on the brakes, rear-end is a little light, moves around a little under super hard braking.
Bike packs up on the first bump (feels like it has run out of travel, and the rebound isn't letting it back out). Just hits, bottoms, and then skips across the bumps.
With the rebound adjusters all the way out, the forks visibly return too slowly, just manually pumping the forks.
I honestly never really thought anything was wrong.
I had the forks/valving done by one of the best, believed it to be dead nutz correct. Had it adjusted and tweaked by a knowledgable racer to were it felt really good everywhere except on the bumps. Geometry wise the bike is dynamite!
I figured the problems over the bumps was me tightening up and clenching the bars, inducing it. Always felt like if I was more relaxed over the bumps the bike would be fine.
I finally tried that at Putnam a couple weeks ago, stayed light/relaxed on the bars and carried my speed over the bumps. Instantly packed up and chattered. I stayed relaxed and kept doing it, and the same result. Went faster, same result.
I asked guys that were going the same pace as me if they were chattering in T2 and T9, and they said they couldn't feel any bumps.
Right then I knew something was wrong. My zip tie was also at the bottom.
I went to Jay Q and he showed me correct rebound action on his forks, and mine is way slower in comparison, and I don't have any adjustment left. It takes about .5-.7 second for my forks to re-extend.
Then I checked the rider sag and I was at 30mm. I believe I am supposed to be at 35. I am sure my tuner friend cranked them down due to seeing his ziptie getting crunched when I would pit. I didn't know anything about suspension, all I knew was he made the bike a lot better, even in the bumps. I figured my ass-clinching in the bumps was mental...I just foound out it's not :wah:
I figured if I could keep the sag at 30mm, add some oil to keep it from bottoming, it would help some. Also thought I could remove some of the Ohlins 15wt and replace it (and add 5cc) with 7 weight, it would dilute the oil to a lighter vicosity and reduce the excessive rebound.
Was also thinking of adding 1-2 pounds of air in my front Mich to aid in faster rebounding (of the tire at least).
I know this is all a bandaid, but no time to ship out forks till after GIR. I blame this on me for not learning about suspension sooner so I could have caught the problem...NOT the guy who tuned them.
If you're at 30mm of rider sag, you on the bike compared to fully topped out, and you've got available preload, it almost sounds like the springs are too stiff.
Stock springs, according to Race Tech, are .95's. I'm betting that's not bad for someone in the 180 range. You're making it sound like you weigh more?
Might be worth rechecking sag, certainly.
Race Tech is also saying that the forks have a long top out spring, thus they say that 35mm of sag is required minimum.
Could be possible that the spring is right to heavy, maybe there's an incorrect spacer in it for racing, or there was a modification done to the top out spring. Didn't the individual that did the work provide you with a baseline idea of where to start up?
Either way, with talk of the rebound being as slow as you describe, that would cause problems independently. Too slow of rebound is a good way to toss yourself on the ground. Could be a mechanical or an assembly issue.
Oil height? Don't know off the top of my head at all. A service manual will give you a number that would probably be lower than what one would set up for on a racing motorcycle. Might be worth finding that.
With too much oil, you could have a bottoming problem too when you run out of air compression.
Something is not right with the forks based on the info provided - rebound all the way out would (if memory serves) make the forks as fast as possible and a half second to return to original position from comrpession sounds slow - how much stiction did you find in the forks when you measured sag?
I'd look for bite marks on the fork tubes... Jo Jo is one mean son of a bitch!
Quote from: tstruyk on May 12, 2010, 01:26:21 PM
I'd look for bite marks on the fork tubes... Jo Jo is one mean son of a bitch!
True story!!! :biggrin:
I didn't see any posts about these two points of interest.
1) Make sure the correct adjuster is being used for Compression damping and then rebound damping.
2) It is possible to overtighten the adjuster locking it into a full slow mode. I've had an R1 that I had bought found stuck that way. I've also seen a freshly built set of forks adjusted incorrectly that displayed in the same manner.
Mark
Not sure what weight fork and shock oil is suggested for stock suspension or whatever components you have in there, but Racetech suggests using their US1 oil for your bike (3.5 to 5 weight oil). If that's accurate for your suspension set-up as well, then 15 weight oil will definitely cause a rebound problem!
Too heavy of oil should also be effecting your compression damping, even if your springs are too weak for you the excessive damping may be preventing the forks from bottoming out immediately during your hardest initial braking. But even with really slow damping the suspension will still eventually find bottom if the springs are too weak, which may be the case when your turning.
Want to thank everyone here for all of the help with my fork issues.
I took the bike to WFO-Motorpsports and had Jerry go over it. Everything everyone here was saying was confirmed. My fork springs are a hair too stiff, the fork oil is too thick for my rebound valving, and the oil level was way too low. WFO is going to service them and get them correct.
Thank you all again for all of the help!!! 8)
And what about JoJo???
Quote from: tstruyk on May 13, 2010, 04:56:32 PM
And what about JoJo???
Speedy's trying to keep him on a metal free diet.
Um its a little known fact JoJo eats lead and shits bullets... true story
Quote from: Speedballer347 on May 13, 2010, 03:33:13 PMMy fork springs are a hair too stiff, the fork oil is too thick for my rebound valving, and the oil level was way too low.
The oil issues explain the damping problems, but too heavy of springs should have helped to prevent the suspension from bottoming - going to lighter springs seems wrong for avoiding the suspension from bottoming. The main thing I can think of that explains the suspension bottoming with stronger springs would be if your oil was so low that the compression valving was possibly cavitating and no longer able to do it's job (or air was trapped in the cartridge from never having been bled properly in the 1st place). Low oil may also not allow the anti-bottom out feature of your forks to work either.
Hopefully the current changes are going to fix the problem. :thumb:
I'm betting that too low of an oil level increesed the "air spring" so much that the springs were doing all the work, and like GSXR Racer said it allowed air to get into the compression valving throughing that way off.
Oh and JoJo is Evil!!!!!!!!!!!!!!...He eats rabbid racoons for breakfast!!!!!!
Quote from: duckracer996 on May 14, 2010, 11:43:39 AM
Oh and JoJo is Evil!!!!!!!!!!!!!!...He eats rabbid racoons for breakfast!!!!!!
JoJo is in deep depression since wednesday night when he f-i-n-a-l-l-y caught a 20lb raccoon and got the poop beat out of him :wah:
He is sad.
We all have to be super nice to him at the Gateway tracksetup and get his spirits up :cheers:
Quote from: Speedballer347 on May 10, 2010, 10:23:35 AM
SUPER Dave!!!! 8) I was hoping you woould have advice in this thread
I can't get the forks shipped til the following Monday after the MCRA trackday. The forks were already rebuilt and the right springs/valving were supposed to be in there. I always just figured they were...I knew nothing of suspension.
GSXR1000 2005.
Rider sag at 30mm front. 4 lines of preload showing. Rebound all of the way out. Compression 6-out (19 or 20 click range)
The forks bottom so hard the zip-tie leaves indentions in the fork's dust-seal.
Don't know if it is bottoming on brakes or bumps, or both.
Bike feels great on the brakes, rear-end is a little light, moves around a little under super hard braking.
Bike packs up on the first bump (feels like it has run out of travel, and the rebound isn't letting it back out). Just hits, bottoms, and then skips across the bumps.
With the rebound adjusters all the way out, the forks visibly return too slowly, just manually pumping the forks.
I honestly never really thought anything was wrong.
I had the forks/valving done by one of the best, believed it to be dead nutz correct. Had it adjusted and tweaked by a knowledgable racer to were it felt really good everywhere except on the bumps. Geometry wise the bike is dynamite!
I figured the problems over the bumps was me tightening up and clenching the bars, inducing it. Always felt like if I was more relaxed over the bumps the bike would be fine.
I finally tried that at Putnam a couple weeks ago, stayed light/relaxed on the bars and carried my speed over the bumps. Instantly packed up and chattered. I stayed relaxed and kept doing it, and the same result. Went faster, same result.
I asked guys that were going the same pace as me if they were chattering in T2 and T9, and they said they couldn't feel any bumps.
Right then I knew something was wrong. My zip tie was also at the bottom.
I went to Jay Q and he showed me correct rebound action on his forks, and mine is way slower in comparison, and I don't have any adjustment left. It takes about .5-.7 second for my forks to re-extend.
Then I checked the rider sag and I was at 30mm. I believe I am supposed to be at 35. I am sure my tuner friend cranked them down due to seeing his ziptie getting crunched when I would pit. I didn't know anything about suspension, all I knew was he made the bike a lot better, even in the bumps. I figured my ass-clinching in the bumps was mental...I just foound out it's not :wah:
I figured if I could keep the sag at 30mm, add some oil to keep it from bottoming, it would help some. Also thought I could remove some of the Ohlins 15wt and replace it (and add 5cc) with 7 weight, it would dilute the oil to a lighter vicosity and reduce the excessive rebound.
Was also thinking of adding 1-2 pounds of air in my front Mich to aid in faster rebounding (of the tire at least).
I know this is all a bandaid, but no time to ship out forks till after GIR. I blame this on me for not learning about suspension sooner so I could have caught the problem...NOT the guy who tuned them.
Now crush my GIR dreams :biggrin:
.
Any advice you can offer Dave, is super appreciated!!! :cheers:
You have a combination of things going on. You fork spring rate is too soft allowing the bottoming.
The too stiif of rebound with minimum damping at the screw is because of a damaged fork rod. I had a problem with my rebound rods where the preload cap actually broke the rebound pieces in the rebound tube causing the exact same problem you describe. You'll need good rebound tubes to replace the broken ones (usually means purchasing good used forks). And replacing the rebound tubes in the forks you now have.
You might be right.
With the rebound screws all the way out the bike has too much dampening. With the screws all the way in, hardly anything changes, doesn't increase rebound dampening much worse than it is with them all the way out. Something surely could be broken. We will check for broken parts. Thanks! :cheers:
The majority of damping is controlled by the shim stack on the damping valve, the external adjuster on your suspension ultimately controls what is more or less nothing more than a bypass around the shim stack. What your actually controlling with the damping screw is nothing more than fine tuning the rate at which a small percentage of the suspension oil travels from one side of the damping valve to the other.
The small bypass port (hole) around the shim stack is designed to work with a certain oil viscocity, as the oil gets thicker that bypass port will become less and less effective in changing the damping characteristics of your suspension. When you turn the damping screw all the way in (till it lightly bottoms out and blocks off the hole completely) the bypass hole is not being used at all and the shim stack on the valve is controlling all the oil flow (there may be a very small bleed hole in the actual damping valve as well, but it's not externally adjustable). As you turn the screw out it uncovers the bypass port and starts to allow some of the oil to travel around the damping shim stack. The greatest change in damping (by the damping adjuster screw) is in the very first turn of that screw because it's starting to unblock the bypass port, the further away from the bypass port the screw gets the less effect each turn of that screw has on damping. If the damping screw is turned all the way in till it bottoms, and then overtightened, it can potentially damage the end of the damping screw and/or the bypass port that it controls. If the tip of the screw was damaged it would most likely effect the first turn of the adjuster the most (not allowing good fine adjustment) and shouldn't really effect the later turns. If the bypass port itself was damaged (somehow crushed down smaller) then it could potentially effect the entire range of damping on the adjuster, but that's unlikely to happen.
I still believe it was the oil thickness that caused the damping problem.
Jerry at WFO fixed my forks 8)
He measured the oil level and it was 5mm shy of max. He said the rebound valving was a bit much. Also said they were assembled to where 5 clicks of rebound range was missing.
He completely dissasembled and cleaned them. Put in fresh oil and added 5mm of fluid to the level. He also assembled them that now I have 5 more clicks of adjustment.
Now with the rebound adjusters all the way out, the forks manually feel perfect. Rebounds noticably faster. He says he will watch my zip-tie at the track and will add more oil if necassary.
I am happy! 8)
:cheers: