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Old 08-30-2011, 09:58 PM
Supercourse Supercourse is offline
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Location: British Columbia, Canada
Join Date: Feb 2008
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Mein Auto: 2004 X3 2.5i
Originally Posted by Evlengr View Post
They are reporting that after three months of wear with new brakes that the rotors are actually the same or more in thickness. C'mon what kind of BS is that.
I'll play Devil's advocate here .......

Rotors do build up a microscopic layer of pad material, because of the nature of disc brakes and the heat involved.

They are both sacrificial components, but not independent of each other.

This is why bedding in of new pads can be important - to get that initial transference as evenly distributed as possible.

And it's why using old pads with new rotors is not normally advised, because the old pads are not likely to be worn perfectly evenly.

Using new pads with old rotors is more acceptable, but also not optimal, regardless of min. rotor thickness considerations.

New pads and new rotors provide the best starting point for establishing long-term braking performance.

So, after a few months with new pads on old rotors, could the rotor thickness really have increased?

Nah, not really - but other that inaccuracies in measuring, they could be measuring now at a spot that has a high point of pad material transfer (as already mentioned by madurodave).

So that could account for the 0.01 mm. but the point is that there is still a way to go until min. thickness is reached.

More than measuring inaccuracy I would say, so in hindsight it might have been best to wait until closer to the 8K miles remaining under no-charge scheduled maintenance.

If an independent measurement finds min. spec. reached, would this really lead to the dealer readily coming up with new rotors?

Or more time-consuming back and forth discussion?

Scuff up the rotors with emery cloth for a fresh start, do the belated bedding in process, and try the dealer again in a few months?
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