Surface hardening due to excessive heat (read seizing caliper). The
rear calipers have park brake-actuated pistons. Seized park brake
cables will cause the rear calipers to stay applied. The inner pad
gets the brunt of the force.
JR
Dweller in the cellar

On Mon, 22 Jun 2009 01:12:11 +0000 (UTC), David Lesher
wrote:

A friend's Audi sedan made some funky noises while braking.

Pulling the solid, one-piece, rear rotor revealed why. The outer surface
was fine, but the inner one showed the usual ~~smooth surface, and
several patches where the surface was anything but. It was as if the
surface was a plating or veneer....and flaked off. Underneath, the steel
was rusty and visibly porous. This was in several spots from dime to
quarter sized.

While none of us are 8-5/40Hr auto mechanics, between us we have multiple
engineering degrees, and many decades fixing our own cars; we've never
seen anything like such.

I'd assumed rotors are cast then turned, for both size and
thickness. True? Are they hardened at some point? What could explain
pores in such?
--------------------------------------------------------------
Home Page: http://www.seanet.com/~jasonrnorth
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No skeletons in the closet; just decomposing corpses
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