View Single Post
Old August 28th 08, 05:17 PM posted to
Jeff Strickland
external usenet poster
Posts: 1,481
Default E39 Vibration on Braking - help please !

"holdgaj" > wrote in message
>I have vibration of the sterring wheel on braking on an E39. There's
> no vibrattion through the brake pedal. Just had a diagnosis from a
> garage - "brake discs (rotors) need replacing".

That's my diagnosis too.

Warped rotors can be felt through the pedal, but they are not always felt
there. They are felt in the steering wheel.

I can't address the difficulty of replacing the bushings, but I've heard
here many times that it is a DIY-kind of job. If you have the ability to
install new rotors, you can do the bushings.

Warped rotors are a result of heat, which is a byproduct of worn brake pads.
The pad material, when thick, does not generate much heat at the surface.
When the pads wear, the heat that normally sinks out of the pad backing
plates does not sink as well, the pad material acts as a heat sink/insulator
when the pads are new, and this characteristic is lost as the pads wear out.

If the pads are close to end life, AND you have to mash the brakes to stop
short from a relatively high speed, then the heat generated can warp the
rotors. If the pads are new under the same conditions, the rotors will
survive the ordeal and work well for the next stop. When the pads are worn,
the next stop can be shakey.

The suspension parts (bushings) will generally load up under braking, and
remain under the constant load until you stop. This means that the worn
bushings can cause noises when going over speed bumps or on rough roads,
where the suspension parts move around, or they can cause the car to pull to
one side as the geometry changes under braking. Suspension parts (bushings)
do not generally cause shaking under braking. You may need bushings, this is
common, but I'm not sure that shaking is the first sign. Indeed, worn
bushings can make the effects of warped rotors even worse, but if the rotors
are in good shape, you ought not notice worn bushings during braking.

You should be able to replace both rotors and all four pads -- always
replace brake parts in Axle Sets, never peice-meal brake service -- for
about $100-ish in parts.

On reading the Brake
> FAQ I see that worn suspension bushes can cause vibration of the
> stereing wheel. The vibration is worse at higher speeds. I would have
> thought that warped rotors would be felt through the pedal as well as
> the steerrng wheel. I'm on a tight budget, and don't want to replace
> the brake discs unecessarily. Can someone confirm that warped rotors
> would be felt through the brake pedal ? Or not ? I'd also be
> interested in the difficulty (i.e. cost) of replacing the suspension
> bushes *& which ones need to be replaced.
> Its a E39 528i 50K miles.
> Any help appreciated