View Full Version : Brake rotor maintenance

07-24-02, 11:41 AM
Hey all,
I was wondering how I can check my rotors myself. Can I buy something to measure the run-out and the minimum thickness? I have a verneer caliper set that I can run around the rotor and watch for the thinnest portion of the rotor but can I get something more accurate/efficient? Can I measure my "out-of-roundness?" I have a 2001 Malibu with 21000 miles on it, and it feels like the rotors are going. Thanks for your help.

07-24-02, 03:44 PM
A vernier caliper will work fine for checking rotor thickness, but you'll need a dial indicator setup (magnetic base, flex and/or rod arms, etc.) to check lateral runout. It's still in warranty - why not just let the dealer do it?

07-24-02, 06:42 PM
Wow, only 21K and the rotors are shot? Are there grooves or stress cracks present on the rotor itself? Is the outer lip of the rotor face have a raised lip near the edge? I'd like to think that rotors would last longer than that, but driving conditions could play a part. What about the pads?


Tom Bryant
07-25-02, 12:04 AM
Rotors developing excessive runout has been a big problem for a long time. Aftermarket ones made from inferior materials go bad sooner. They can be trued up by having them turned but the shake will be back eventually. On older cars I just live with it. On something as new as yours, let the dealer replace them under warranty as John said.

One of the main reasons for runout developing is improper torquing of the lug nuts. The impact zip, zip, zip, will warp them faster that anything. If you get your tires rotated or the wheels are removed for any reason during service work, do yourself a favor and loosen and re-torque each lug nut with a torque wrench to specs listed in the owners manual once you get it home. It does make a difference in how long a rotor will last. Usually alloy wheels torque to 80-85 lbs. Steel are less but I'm not sure what.


07-25-02, 07:29 AM
Well, I thought the brake hardware was only warranted for 12k or so. I donít know about stress cracks I havenít looked for that. There is a small lip on the outside edge Ė I would guess 21k worth. The pads are in great shape. I am hoping itís the rotors that are bad and not anything more complicated. As far as impact wrenches, I hate them, I am the only one who has touched the car so far, and I sure didnít use an impact on it. I donít like it when I go to check brakes or change a flat and end up shearing a wheel bolt Ė Iíve broken three. Now when I get tires put on my cars I take the old ones in loose and put them back on myself at home. When I get alignments I stand at the window and make sure they donít use impact wrenches after I have told them not to. I have enough trouble getting them off after a wrench but my wife could never do it if she were changing a flat. Anyway, Iím taking the car in for some other warranty work this weekend and planning on leaving it a couple of days while sheís out of town, I guess Iíll ask if theyíre still covered.

JohnZ, where would I get one of those dial indicators? I have two other cars that certainly arenít under any warranties :) . I have done all my own work since I was just getting into college Ė mainly due to lack of funds. I hate mechanics getting in and out of my vehicles with dirty hands and then touching everything inside the car. I had a black Sonoma that I put in the shop this past January. It had some EGR problems that I could not figure out and was in a hurry to sell it (I agreed to sell the truck immediately after I got my vette Ė good trade I thought). This mechanic tried to talk my into selling him my truck CHEAP by telling me what all was wrong with it and how much time and money would be required to fix it. I told him to just put it back together and I would contend with the rest of the issues. I picked it up the next day. It smelled like smoke for a couple of days and I found a cigarette he had snuffed out on my rubber floor mat in the back of the cab and he left the butt under my seat!

Thanks for the help guys.

07-25-02, 12:07 PM
The Harbor Freight catalog is a great source for dial indicators and accessories; you don't need Mitutoyo-level accuracy for most automotive chassis work.