brake rotor runout 0.005 inch

[Mr._Graybeard]

Hi folks -- I had a LF sticky caliper awhile back (the smell gave it away) and since then I've had a slight vibration at 75 mph plus a kind of pulsating noise that sounds a little like a tire out of round. I replaced both front calipers. Tires checked out OK but I noticed the LF wheel was getting slightly warmer than the right -- not hot, just warm -- after my lengthy commute home. I dug out my dial indicator and found I had 0.005 runout on that rotor.

Think that's bad enough to produce my high-speed symptoms? I don't notice any pulsation when braking. I'm tempted to have rotors turned -- they're Balos with 20K miles, mostly highway.

TIA --

[Tiger]

I'd have them turned since your rotors are so new.

[Mr._Graybeard]

Yeah, that seems logical. I've always been told BMW rotors should be replaced vs turned, but these are still plenty thick and the runout isn't that much. Worth a try, at least.

[Bill R.]

I don't think thats enough variation. I would take the rotor off and clean the hub and rotor, then i would measure the rotor at different points for thickness variations, not just for runout. If you have a random orbit sander i would lightly rough up the surface on both sides to get any brake pad buildup off the rotors and then try them again.

[Mr._Graybeard]

I don't think thats enough variation. I would take the rotor off and clean the hub and rotor, then i would measure the rotor at different points for thickness variations, not just for runout. If you have a random orbit sander i would lightly rough up the surface on both sides to get any brake pad buildup off the rotors and then try them again.

Thanks for the response, Bill, but I'm afraid I checked back in a little late. I had the disks turned, and while I was in there I cleaned up the hubs and lubed the caliper guide pins.

The result is, definitely have less vibration, although I'm still hearing some noise. It's probably the tires (Conti DWS with 30k miles). I very well may have been able to clean up the disks with sander as you suggest. My pads are Hawk HPS -- they do tend to be a bit noisy under the best of conditions, and if they were catching some pad deposits on the rotors I could see where they might produce a little vibration.

It was never a very significant shake -- my wife didn't notice it at all. But I put on a lot of miles, so have plenty of time to ponder automotive behavior as I go down the road..

I'll keep your advice in mind should the issue crop up again.