RE: Serious Steering Wheel Vibrations- whoever can solve this gets $20

["Richard Arnold" <richardarnold@xxxxxxxxxxx>]

> -----Original Message-----
> 
> Here's the deal.  1988 BMW 735 with ABS.
> -  Brakes worked great, no vibration at any speed off or on braking.
All
> pads were getting worn and needed replacement.
> -  Replaced front and rear pads and bled through all new fluid (cheap
> skate
> method of a brake job)
> -  The car then immediately exhibited significant wheel jerking at
around
> 40 to 45 MPH on light to moderate braking. Only at this speed.  Can
occur
> braking from high speed coming down through the 45mph mark, etc.
> -  Replaced front and rear rotors and front calipers to try to
resolve.
> Problem did not go away.
> -  Re-bled system with manual bleeder.  Problem still there!
> -  I have had the tires balanced twice and have tried two sets of rims
> vibrations with both sets.
> -  Then took apart all four calipers and cleans and lubed
mounting/slide
> pins, etc.  Problem still there.
> -  BMW shop checked for worn bushings and components- none!
> -  Alignment was done very recently, but before initial brake job.

Could it be something in the ABS sensor, thinking the wheel is locked
under even moderate braking?  I don't know how BMW does it but my
Mercedes uses a sensor located at the front wheel bearing.  A Toyota I
had used a notched rotor hub and a proximity sensor that detected
rotation, or absence thereof.  If something is amiss with the system,
the car could be applying ABS when it should not.  That would cause
vibration. Harmonic noise could be why it is only at certain speeds;
similar to why out-of-balance wheels only vibrate at certain speed
ranges.

Good luck,
Richard Arnold
'73 Spider
'87 SDL 
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