E92 Rotor Max/Min Specs

[purcellj]

Short story: BMW dealer says "your '12 E92 pads are fine at 38k, but your rotors are near the minimum spec. But it passes PA state inspection." They did not provide any details on the rotors depth/specs. Yes I did ask. This just doesn't sound right to me.

Back story: I bought the car in '13 at 7k. No brakes/rotors were changed between 7k and 38k (aka while I owned it). I have performed fluid changes at prescribed intervals. I have no indication that the prior owner did anything crazy (track days or otherwise) with the car.

So @ 38k I BELIEVE it's on OEM ORIGINAL pads and rotors. ** Yes this does contradict the BMW dealers statements. **

I will be switching from summer to winter tires shortly. I want to measure the rotors and truly understand if the rotors are toast. I have no problem replacing them, but replacing rotors before pads during normal road driving seems strange. (aka no track days, or crazy start/stops)

What is the brand-new stock rotor thickness?
And what is the minimum thickness?

!! Sorry I will not be calling the dealer out. So please don't ask. In the past they have been pretty good to me.

I have a local exotic mech that will do the brake and/or rotor work, but I really don't want to waste their time if it's not worth it.

I did search a couple of OEM parts dealers but they don't list dimensions.

TIA
John

[Kisenwether]

OEM BMW rotors have the min thickness engraved into the hat of the rotor.

I think these values are right,

Front:
30 mm new
28.4 mm minimum

Rear:
24.0 mm new
22.4 mm minimum

[aswy6]

I have 83k miles on mine and its still on Factory rotors and pads. however they are almost done. I would definitely measure

[pbonsalb]

My original rotors were done at about 90k miles. Might have been even more than done. Mostly highway. City driving should use up rotors in fewer miles.

[wyatth]

With street driving I regularly read lifespans of 70k+.

I had a PPI on my car performed at EAS at 47K and they said the brakes were great. During the recent rod bearing work (at 49K), my mechanic said the rotors are near their end with a big lip on the backside. I'm in the same boat as you. Will get a third opinion then figure out what to do. Chapped, putting a lot into maintenance right now and wasn't planning on brakes.

[purcellj]

Thanks guys! All great info! Depending on weather I might pull the fronts to measure this weekend.

Again Thank You!

[aswy6]

Originally Posted by purcellj

Thanks guys! All great info! Depending on weather I might pull the fronts to measure this weekend.

Again Thank You!

You dont even need to take off the fronts, just stick the tool through the wheel. Rear you need to take off because the shield is on the way

[purcellj]

Kiswether: Your dimensions were correct for my car per the hat engraving.

aswy6: This is kind of correct (at least for me). The rotor has a lip, so adding pair of nickels between the caliper teeth is tricky, but I'm sure it can be done.

So with the front min being 28.4mm, I'm getting readings of 28.6x towards the outside and 29.0 in the middle of the rotor.

Being conservative, it looks like I'm fine for another 5k (38k/1.4*1.6).
Again thanks all!

[PACarGuy]

Yup, you should be good for a while.

Rotors and pads are really not hard to do on this car if you want to save some $ when it's time to swap them. OEM rotors from FCP are ~$240/each and you get lifetime replacement included.