'87 R65 front wheel

[fritz1]

This bike gets into a tank slapper at 70-80 kph........not above or below, when I take one hand off the bar!
I've checked, adjusted, and greased steering head bearing, wheel bearings. Changed fork oil to 10W. Replaced front tire (Metzeler ME33).
Found that rim has .040" runout. (2.50 x 18, 4 spoke 'Y')
Any suggestions would be gratefull.

[R80RTJohnny]

Hello,

You may want to check the fork alignment. BMW had a service bulletin in the late 80's or early 90's regarding this problem.

I too had a similar problem with my R80RT but I've since changed to Michelin tires stock size and now sport a Progressive Suspension rear shock and have not had the problem in many years.

Will have to check it out. If I'm not mistaken this tankslapper would be more prone if you are in a curve?

Keep us posted.

Good luck

[pmdave]

Did you disassemble the steering head bearings? The races can become "notched", which causes some strange dynamics. The front wheel wants to recenter itself back into the available notches. The fix is to replace the bearings, including both races and rollers (or balls on some models) When assembled, put the bike on the centerstand and adjust the bearings just tight enough that the front end will turn itself to either side easily but not quickly. If it bangs to the stop, snug up the bearings a bit more. Tapered rollers require some preload to work correctly.

Second, check out what's happening at the rear end. Are your wheel bearings snug? Swing arm bearings? Just a little play in the rear end bearings can cause an oscillation at the front.

Third, take a very close look at your front tire. Scalloping of the tread is not uncommon on BMWs, and can contribute to wobbles. If there are obvious scallops, replace the tire. Also, consider the profile of the rear tire. If it is worn flat across the center, there will be "shoulders" that contact the pavement off center, and that can contribute to strange handling. When you're replacing tires, stick with the sizes in the manual, don't get creative.

pmdave :type