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bwheitman 11-10-2003 03:40 PM

Turn Rotors?
I have to do my brakes this weekend since the little light on the dash tells me so (ha ha). I was wondering if the rotors are to be turned? I remember seeing on some prior posts that they are not to be turned. If I don't turn them do I have to replace them? This is the first brake pad replacement on a 96 SL320. Thanks !

tecqboy 11-11-2003 08:50 PM

The light comes on because the pads are worn down enough to let the embedded sensor wires ground to the rotors. Time to replace pads and get new sensors too. When you get it apart it will all become obvious. If the rotors are smooth and have no signs of a deep wear groove from the pads, or warping, keep 'em. It's a judgement call. New rotors aren't all that expensive, but replacing them requires torqueing, and hence special tools. So, I replace pads myself at a ratio of 2 to 1. That is, new rotors every 2nd set of pads. Search this forum for excellent instructions on doing the job. Then decide on hard pads / soft pads / no dust / dust. There has been so much said about brakes. BTW, most guys do not recommend turning the rotors for various reasons. As they are cheap, just replace them. ttt

cbdo 11-11-2003 10:02 PM

I'm told that rotors from somewhere in the 80's on are thin enough that they shouldn't be turned, as there's not enough metal left. Mine will be replaced when the pads are, since it's the first brake work I'll have had done and I'm not sure when the last was.

G-Benz 11-12-2003 12:14 PM

The engineers deliberately designed them to be just stout enough to be durable, but thin enough to dissipate heat quickly.

When turning the rotors, if enough material is removed to make the rotors thinner beyond spec, then the extreme heat they are subject to during normal use will cause them to warp excessively.

Result: New rotor replacements guess what? You were better off replacing them anyway. ;)

DavidSoine 11-12-2003 01:58 PM


The way to tell that new rotors are needed is to MEASURE THE THICKNESS with a micrometer and see if they are in or out of spec, or getting close to out-of-spec. The minumum thickness is usually stamped into the rotor itself.

Turning rotors can cause as many problems as it alleviates - always replace rather than turn the rotors if at all possible.



bwheitman 11-13-2003 12:08 PM

Hey everyone! Thanks for all your help! you are just great!

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