Sounds like rotors!

 

Sounds like they need to remove the rotors and check runout. Rotors or pads, one or the other needs replacement. Your car should brake absolutely smooth and straight from any speed and regardless of how hard you are on the brakes. Anything less than that they need to fix.

 

May also be a frozen piston causing uneven wear. Remove the pads, and check their wear characteristics and check the dust boots.

 

I'm with the other guys on this. That's not normal wear at only 3k miles unless you ride those brakes like your old lady or live on top of Pikes Peak.

Take to another dealer and get a second opinion as the others have said. I have a C2S and baby my car. Used to drive a limo in college so some driving habits just spill over. I have 10k miles on my car and 85% pad left on all 4 corners. I know another fellow here on Rennlist with a C2 manual and he loves standing on his brakes and he still has lots of pad left as well with 8k miles on his car and he lives in the hills like me. Steering wheel shimmy is almost always warped rotors like the boys said. Any really hard stops and in some standing water?

 

Tracking your car causes the rotors to wear more quickly. I have 8k miles on my car and am on my second set of rotors and 4th set of pads after lots of track days, for example. But wear does not automatically equate to vibrating brakes.

Differential rates of cooling can cause the rotors to warp, which will cause brake vibration. For example, if you get the brakes really hot, say going down a steep twisty road, then sit at the bottom of the hill for a few minutes with the brakes on, the portion of the rotor under the pads will cool much more slowly than the portion of the rotor exposed to the air.

Certainly 3k normal street miles is not enough to wear out a set of rotors, even with some track days thrown in. Especially if you followed normal brake in procedures. But it is possible to warp rotors in one outing. That is why you cool the brakes off on the last lap of a track session, and some folks even take a few laps around the pit. And you never put on your parking brake after being on the track.

With all that said, I did get a set of rotors replaced under warranty on an E36 M3 that had been heavily tracked but had about 4k miles on it. The mechanic claimed that the brakes were "abused" (rotors were blue) and I fought back that it is not possible to abuse brakes, just use them hard. Since the M3 brochure bragged about the braking capability, I showed the brochure to the service writer who got the mechanic to begrudgingly replace them for free.

Give it a try at a dealership or two, maybe you will get lucky.

 

I'd just ask them to replace the pads and rotors under warranty.

 

Agree with Chuck - it is usually pad material deposited on the rotor. You might be able to improve it by a bedding-in procedure or sanding the discs. See StopTech FAQ on this:
http://www.stoptech.com/technical-su...nd-other-myths

Does it only happen when stopping from 70+? If you brake firmly, does it get worse or better? Have you dinged a wheel? If it doesn't happen at low speed, I would question whether it is an alignment, balance, or bushing issue, not necessarily the brakes. Any of these should be warranty item (except the injured wheel, I suppose).

 

Just got of the phone with the dealer, the brake pads are fine. What needs to be changed are the rotors and they recommend changing the pads. All is under warranty.

 

Definitely always change pads when changing rotors in my books. Did they say what the cause was?

Interesting issue from another German manufacturer that I've suffered through. The latest version of the MB GL SUVs have had terrible rotor warping issues. They believe it has something to do with a contamination but has been a continuing problem. Very different equipment I know.

 

I found it interesting that it only happend at 70mph. if rotors, it should be related to break pressure and not vehicle speed.
So hard breaking from 40mph should also cause the vibration. It will get amplified at higher speeds but should also be there at lower speeds.
If only occuring at higher speeds, could be tires or something else in the suspension/steering.


Keep us posted after you get it back.

 

Why? This seems like an awful waste of money. Unless the rotor is worn unevenly (which is easy to tell), there is no reason to change the rotors because of pads. That's adding a huge cost increase for no real advantage.

 

You may have misunderstood me - if you are changing rotors due to an issue, change the pads.

As an FYI with the MB issue - it was the pads that were contaminated and if they just switched the pads people were back within 5 - 10K miles for new rotors again.

If it's all under warranty, switch it all out.

 

7K miles and I need another set of rotors.. This is the second time it happens. I put around 4k miles since they last changed them which the dealer claims was a factory defect.
Dealer has no idea why it happened again..

 

they are not *bad* nor, unless you are either overlooking telling us about your driving history, or there is a manufacturing fault in both the pads/rotors, do they need replacing

Ok here is the scoop:

1) rotor replacement:

Rotors are only recommended to be replaced as per the factory
maintenance schedule if:

a) the rotors thickness is less than the minimum permitted

b) if there are cracks (caused by thermal expansion/contraction) around
the drill holes that either exceed 6mm (I think) or if they extend to the
edge of the rotor itself

2) pad replacement:

pads should only be replaced if they are sufficiently worn to activate the
wear sensor, or are likely to expose their backing plate to the braking
surface (if wear is uneven)

The problem I believe you are experiencing is a common one where pad material is deposited on the rotor surface, 'glazing' it, resulting in vibrations
while braking.

see this article: http://www.zeckhausen.com/avoiding_brake_judder.htm

+1

 

thats nuts ... its something else.