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This past weekend I used my new dial indicatior to measure run-out on my front rotors. This was my frist time doing this. I set up the magnetic base on top of the brake calipher and then adjusted the needle of the dial indicator to touch the side of the rotor. I then set the face of the gauge to a reading I could easily see and then turned the rotor one full revolution (I took about five readings per rotor). The TIR I measured at each rotor was .002. Did I do this correctly? BTW, the surface on each looks like an old 45 LP. Should I recondition the rotor surface with the rotor resurfacing product sold by 3M? Lastly, the drivers side rotor had the following markings: GM 26; 3989527; G250.
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Re: Measuring Rotor Run-Out
John
It sounds like you checked run-out correctly and 0.002 is fine. I did not understand your reference to a 45 record. But if there are groves you can feel with your finger nail, I suggest you give them a clean up cut. It's the rear rotors that can give you run-out problems if they are not cut true with the spindle. Any good shop should be able to cut the fronts without issue.
Bill -
Re: Measuring Rotor Run-Out
Bill,
What I meant by that comment is that the pattern on the rotor surface shows the same type of directional marks as the circular needle pattern on the face of a 45 LP. Its my understanding that the rotor surface pattern should exhibit non-directional marks. So, with that said, should I refinish the rotor surface with that rotor refinishing kit available from 3M?Comment
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Re: Measuring Rotor Run-Out
I would leave it alone. The marks you see are normal wear and tear, you will gain nothing by removing them.Comment
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Re: Measuring Rotor Run-Out
Mike and John-----
I would recommend using the 3M rotor surfacing kit to apply a non-directional finish to the rotors and, at the same time, de-glaze them. This is especially important if you are installing new pads, but I'd do it either way.
I don't recommend having the rotors machined unless they have SERIOUS problems. Slight or, even, moderate gooving does NOT constitute a serious problem.In Appreciation of John HinckleyComment
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Re: Measuring Rotor Run-Out
Joe,
Could you discuss in more detail what the 3M rotor kit is and how it is used?
I haven't heard of this before. Thanks JohnComment
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Re: Measuring Rotor Run-Out
John-----
It's a specialty automotive kit manufactured by 3M which includes special abrasive discs, a special backing plate, and a mandrel for use on an electric drill. You simply use the assembled disc with a drill to "sand" the surface of the rotors. The special abrasive compound removes very little of the rotor material, but does remove the glaze and imparts a non-directional finish. It's extremely easy to use and does a perfect job every time. Not too expensive, either.In Appreciation of John HinckleyComment
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Re: Measuring Rotor Run-Out
Thanks Joe.
Great to meet you at Carlisle, enjoyed talking with you and the good Dr.
Ment to ask you what rear gear you are going to run with your Big Block?
Thanks for all your ongoing input to this board.
Best Regards, John LinerComment
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Re: Measuring Rotor Run-Out
John-----
3.36:1In Appreciation of John HinckleyComment
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