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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Mechanical Maintenance: Break-in / Oil & Fluids / Servicing / Warranty > Brake service, no rotor replacement / turning?



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      07-15-2012, 05:59 PM   #1
Brent
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Brake service, no rotor replacement / turning?

I just had my rear brake pads done under my extended service plan. Had the car in for an oil change and they said it was ready for pads even though the computer indicated that they had 5000 miles left. Well, they did the pads under the service plan, but measured the rotors at 18.7 with a minimum tolerance said to be 18.4. They therefore did not replace the rotors, and apparently did not turn them either. Does this sound reasonable? The car has no braking issues - no noise, pulling, or vibration - so I am not overly concerned, just surprised. On my American cars I always turn or replace the rotors so I have a clean surface. I also don't really know how a 0.3 mm thickness before I hit bottom of tolerance translates to miles. It took 52 K miles to wear to 18.7 mm, but I don't know the starting thickness.

Since it was the rears anyway it probably doesn't matter much. My fronts will be due soon. How hard should I fight for rotor replacement in a similar situation with the more critical front binders?
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      07-15-2012, 08:16 PM   #2
Meeni
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Rotors front and rear are different, and left/right are directional (cooling fins orientation) so no turning on our cars.

On my car the rotors were shot at 77k miles. They were slightly under spec, and showed a very visible lip. They start as 22mm, so your's may be under spec before you are through the new installed pads, and when you change the rotors, you'll have to change pads again.

Rule of thumb is to change rotors every 2 sets of pads. pads should last ~40k miles.
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      07-15-2012, 08:24 PM   #3
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Quote:
Originally Posted by Meeni View Post
Rotors front and rear are different, and left/right are directional (cooling fins orientation) so no turning on our cars.

On my car the rotors were shot at 77k miles. They were slightly under spec, and showed a very visible lip. They start as 22mm, so your's may be under spec before you are through the new installed pads, and when you change the rotors, you'll have to change pads again.

Rule of thumb is to change rotors every 2 sets of pads. pads should last ~40k miles.
Thank you! I just learned far more from you than I did from the stealership's "service adviser".

My pads are at 52 K, but I drive primarily highway miles, so going a bit long is no surprise I guess.

Here is a dumb question: how will I know when my rotors go under spec? The sensor only measures the pads, I think. Do I just insist that they measure them in 20 K or something?
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      07-16-2012, 05:28 AM   #4
mlifxs
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[quote=Meeni;
Rule of thumb is to change rotors every 2 sets of pads. [/QUOTE]

Dealer told me this as well. Of course this wasn't the story when they were trying to sell me the extended maintenance plan.
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      07-16-2012, 01:42 PM   #5
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Quote:
Originally Posted by Meeni View Post
Rotors front and rear are different, and left/right are directional (cooling fins orientation) so no turning on our cars.
.
This makes absolutely no sense. The stock rotors are not "directional" and have no oriented internal cooling fins. The p/n's for the left and right rotors are the same. Any rotor that is flat-faced (no slots or holes) can be resurfaced.
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      07-16-2012, 02:24 PM   #6
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The cooling fins on my aftermarket rotors are directional and the p/n are different for left/right. I assumed it was the same for oem rotors.

Now, I just came to realize that not being a native speaker, I misunderstood the meaning of "turned" as "rotated from left to right", while you really meant worked on a mill. They indeed certainly can be resurfaced (in general, not for the op whose tolerance are already on the low side).
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