feeling vibration in my '98 M3 during braking.

Can / should I have the rotors machined to remove run out? Or just
replace?

BTW only 55000 miles on the car, and less than 20000 miles on the
current rotors & pads.


derek_mcquar... (AT) hotmail (DOT) com wrote:

derek_mcquarrie (AT) hotmail (DOT) com wrote:
google is your friend

well the thing is if you have cross drilled or slotted rotors, i would
say that you need to replace as i have never come across a shop who
cuts those and i would also see the the slots and or cross drill holes
presenting a problem to the lathe. If you have standard rotors, check
the service manual, or perhaps even the manual to see what minimum
rotor thickness is. If there is severe warp replacement may be the
only option. If you have standard rotors and after cutting, they still
fall within guidelines for your safe driving id say go for it because
replacement rotors should not be the cheap sort, not on that car.
Happy motoring.

Yes, they are drilled - it is an M3. So no machining then. Ah well.
Cha-ching!

varan wrote:

Yes, they are drilled - it is an M3. So no machining then. Ah well.
Cha-ching!

varan wrote:

<derek_mcquarrie (AT) hotmail (DOT) com> wrote

How did you bend them? Hard stop from speed and then hold on brake?

R. Mark Clayton wrote:
I wouldn't be convinced that they've warped anyway.
Did '98 M3s come from the factory with cross drilled brakes???

If the rotors are not warped, what else could cause vibration only
during braking?

I don't think I drive or brake excessively hard compared to other
people - but then most cars I've driven end up with warped rotors so
maybe I do. Isn't rotor warpage inevitable?

What would cause a rotor to warp prematurely - as I said these have
<20k miles? I know the root cause is ultimately heat, but if the rotor
warps, the heating (or cooling) must be non-uniform if it causes metal
to warp. What can cause that?



adder1969 wrote:

mcquarrie wrote:
Not much.

Maybe you do. Where do you drive? How often do you brake from high
speeds? How often do you have to sit in traffic with the brakes held
after doing so? How many steep downgrades do you have to brake on?
All subjective and also influenced by your personal braking habits.
No; it's not inevitable, but if you tend to warp them on other cars,
the BMW will be little different.

You can warp rotors in a half day on track. Or on a mountain road. Or
maybe even a bad day on the interstate. It's more of an 'incident'
thing than a cumulative mileage thing.
--
C.R. Krieger
(Been there; warped that)