Too much Rotor Runout or Too much time on my hands?

Cash Davidson · **Posted:** Sat May 28, 2005 4:57 pm

I just had four rotors turned at Westgate Imports for $30. Here's the deal - My official Mazda manual states maximum runout as 8 ten-thousandths. I set up my dial-indicator on just the hubs, without the rotors and the runout at the four hubs varied from 10 to 15 ten-thousandths. When I put the rotors on, the runouts went up to 20 to 25 ten-thousandths. I bedded my new Carbotechs and everything feels fine. It seems to me, 8 ten-thousandths is an exceedingly tight tolerance. The Mazda manual recommends turning the rotors while they are on the hub. Presumably this would address the hub runout as well as the rotor runout.

Has anyone else had similar experience or am I the only one who thinks it's fun to spend an afternoon measuring runout. What are your thoughts on rotor runout? Anybody know of a shop that turns rotors while on the car?

DickRasmussen · **Posted:** Sat May 28, 2005 6:17 pm

Cash,

You will probably get more responses on Tuesday after folks get back to work and spend work time on the internet . . . :lol:

Will you be running cooling ducts? If not, the quick answer is . . . the rotors (fronts at least) will be trashed anyway after the track event from the heat and will be beyond saving so it won't matter.

Between heat cracking, grooving, and pad material transfer you may not want to keep those rotors so I would be looking for the best replacement deals now . . . especially if you plan to go back to street pads.

More seriously, the specs for my 2001 Mustang are in the same ballpark and Ford says to do any machining on the car. I've never looked for on the car rotor turning.

Have you seen this article? http://www.stoptech.com/whitepapers/war ... s_myth.htm

Spending Saturday afternoon measuring runout beats lawn mowing, refrigerator door hinge cam replacement, and van headlight plastic adjuster replacement.

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Too much Rotor Runout or Too much time on my hands?

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