Öhlins give me the shakes!
Posted August 05, 2010 - 10:59 AM
I've got a very strange and terribly annoying problem with my 2003 WR450F. First of all, the bike is equipped with a complete Öhlins setup (46mm forks, rear shock and steering damper).
The front end is fantastic when riding on gravel tracks, green lanes and even on massive sand dunes, but there is one major issue I've got when riding on flat and clean tarmac. When riding somewhere between 55-70km/h the front will act as if it was going over 3-4 small bumps, pause for about 1 second, and repeat. What I'm trying to say is my handelbars will shake up and down (not side to side like regular headshake!) for a bit, stop, then again.
If I ride slower the problem disappears, and even pulling it up to 140km/h doesn't make it reoccur, so it's just in that one speed frame. The problem still persists with the steering damper not mounted.
I used to have terrible headshake (sideways) when going over 100km/h, but I got rid of that by lowering the forks in the triple clamps.
Is this issue a compression/rebound setup related one or more of a sag one?!?
Any help is greatly appreciated!
Here a pic of my setup:
Posted August 05, 2010 - 11:15 AM
Posted August 05, 2010 - 11:23 AM
yeah probly not that then. I thought mine was suspension related too but I wrote it off as a tire due to the hell I put it through. Not sure what to make of yours. I assume you've tried differnt cliker settings.
Posted August 05, 2010 - 11:54 AM
Will have to look into the steering stem adjustment. Should I just check to bottom triple clamp is fixed correctly to the steering head, or should I entirely remove it and inspect the entire thing?!?
Thanks for your effort guys!
Posted August 05, 2010 - 01:59 PM
No, I'd first do the 'lock the front brake and rock the bike bike and forth' to check for play. I'd also go over all the bolts to ensure they are snug.
I'd also check the engine, swing arom/links and sub frame bolts too.
Posted August 05, 2010 - 02:45 PM
Posted August 25, 2010 - 11:38 AM
I found the time to install my original '03 forks but sadly the problem is still there
At first I thought by lifting the wheels off the ground I would be able to tell whether my Öhlins had any movement of the bottom tubes when I tried to shake them by hand, but I couldn't feel anything at all.
What I have noticed from riding on smooth tarmac (on either set of forks) is that you can clearly see the entire fork legs below the bottom clamp shake a bit frontwards and backwards during the aforementioned speeds and also when decelerating from about 100km/h to 50km/h.
I'm starting to believe this may be a bearing issue inside the steering head. What do you guys think?!?
I'll have some time this WE to take everything apart and ses...
Posted August 25, 2010 - 02:30 PM
Posted August 29, 2010 - 05:50 AM
I let my dad analyse the problem a bit and after he went for a ride on my bike he said that it is most likely the front end being to stiff to work on the tiny bumps found on tarmac.
I therefore backed out the compression and rebound to the smallest possible and rode it again. Still the stiffness was there.
It seems as though there is simply to much friction of the bottom tubes when they slide in and out of the top tube. How can this be reduced?
I must add that I have a custom preload collar of about 10mm in each fork and an oil level of 105mm.
Should I change anything?!?
Posted August 29, 2010 - 07:19 AM
I thought about the last point and remembered that whilst installing the seals during the last service there was barely any grease on the inside of the dust seal, if not none at all. So I slid the dust seals down, added some grease inside and pushed them back to place. I can now notice that there is a slight improvement towards some friction loss, but not enough...
Feels harsh over small bumps, but using full
Too much spring pre-load or too much compression
• Increase the oil level or change
to softer springs.
• Decrease the compression damping.
• Decrease the spring pre-load.
• Clean the oil seals and scrapers. Use Öhlins
grease 146-01 for regreasing
I also don't think I' really need softer springs like advised in the first point as the ones installed (4.5) should be alright for my weight of 70kg all geared up, or not?
The problem shouldn't be because of my preload since I only increased it after I started having my problem.
Man, this whole thing is a huge mystery to me! I can't understand that I've got this exact same issue on my original UNTUNED forks!!!
Posted August 29, 2010 - 11:09 AM
If I need to replace them, I don't know whether the ones designed for the original forks will fit (the oil and dust seal do fit!). All I can say is i need 3 bushings per fork: 1x with the slit in it to fit on the very top (caoting outside) and 2x with the teflon coating on the inside.
Can anybody give me the sizes of the original 46mm bushings?!?
Posted September 24, 2010 - 07:55 AM
I can safely say that a great deal of my problems are now sorted, but not 100%.
Like you suggested, the wheels may need some balancing to completely get rid of the problem...