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Old 05-09-2010, 08:18 PM   #1
JasonF OP
Gnarly Adventurer
 
Joined: Dec 2007
Location: NoVA
Oddometer: 157
Question vibration..and everything out of round

So I just completed a 650 mile trip on my 07 GSA. After many hours in the saddle I realized that the overall vibration was making the ride quite uncomfortable for me. Specifically, the right hand grip seemed to have about 1/8" of vibration in a down&forward, up&back direction. My right wrist was not happy about the relentless motion. The left grip, curiously, was pretty smooth.

Background:

Bike has 14k miles. My front tire is a Tourance with about 10k miles on it. It still has a decent amount of tread on it, but it does appear to have some cupping. When I spin the front tire+wheel with the bike on centerstand and weight on the back, it is evident that the front wheel has some wobble to it. I didn't dial indicate it but I'd guess 2-3mm side-to-side. The tire itself also appears to be a bit out of round, and I don't know its current state of balance. Replacing this with a new, balanced tire, might be a good place to start.

Then after reading the FAQ on Woody's site, I examined my back tire/wheel. I just had a brand new Tourance tire put on it before my trip and it was balanced, so I know that much is good. Woodys mentioned that some people complain their rear wheels are out of round even after truing, and it's because the BMW final drives actually wobble on an orbit. So I put the bike on the centerstand and ran it up in first gear to about 15mph. Sure enough, the rear tire/wheel was wobbling around pretty bad and I could see the rear brake rotor moving up and down about 1/8" with respect to the caliper. I could also see the brake caliper moving side to side a bit on its slide pins as a result of sideways wobble in the rotor. Spinning the rear tire with the engine off, the tire spins freely for about 2/3 of a rotation but the brake rotor clearly rubs the brake pad harder for the last third or so. I recently had this rear rotor replaced due to pulsing rear brakes, and it felt similar to this prior to replacement. I rarely use the rear brake, and I am very careful not to accidentally drag it while riding.

So based on all of this, everything seems to be out of round. Front tire, front wheel, and the rear wheel and hub.

The bike is still under warranty so I think I'm just going to take it in, explain that it has uncomfortable vibration on the highway, and ask them to check the runout on the aforementioned items against the maximum allowable specs. If its out of spec, I have to think it would be covered under warranty. Anyone have any experience with this? I'm most troubled by the fact that the entire final drive hub appears to wobble. How is this possible? I'm also curious if all the new bikes on the floor would do the same thing. If any of you reading this get a chance, i'd also like to know if yours does the same when in 1st gear on the centerstand. Is it smooth or does the rear end move around a good bit?

I was hoping it was going to be as simple as a new and balanced front tire, but my investigating makes me think theres a lot of stuff that needs fixing.

Thanks

Jason
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