Warped front rotors

[larryejoh]

My original front left rotor warped a while back. I replaced it with a new one from O'Reilly's. When put the first one on it felt alright for a few hundred miles and acted like it was warped again. I put my dial indicator on it and it was .005 out. I went back to O'Reillys and got another. This time I put my hub on with no rotor and my hub is true I put the new rotor on and its still .005 out. O'Reillys said it needed to be turned on the hub. I took it back and they turned it. Now its worse and showed .010 out with my dial indicator. Whats wrong cheap Chinese rotors?

 

[bad 68]

More than likely you have a problem with your brake caliper not sliding in the mounting flange. If it doesn't slide easily your caliper only puts pressure on the inboard brake pad.
This will make if feel like you have a rotor problem.

Brake parts rust. You need to use a wire wheel on a drill/grinder, or just a good wire brush to pollish the mating surfaces of the caliper and mounting flange. Then a thin coat of anti size on the surfaces and you should be good to go.

 

[Apogee]

Most new rotors, even cheap Chinese ones, should have less than .002" runnout out of the box, especially if they advertise that they're ready to install. Most rotors will have substantially less runnout than that in my experience. Given your numbers, it sounds like you may have dirty mating surfaces between the hub and rotor but that's just a guess. If that's the case, your runnout numbers can change if/when you have a tire bolted in place since the rotor is held in with the wheel studs.

Turning the rotors on the hubs should have produced a near-zero runnout assembly. The fact that it didn't points to either shoddy workmanship or some other issue. A hub/rotor assembly should not go into a brake lathe with less runnout than when it comes out...something is wrong. Are your bearing races tight?

 

[larryejoh]

Bearing races are tight, I cleaned the mating surface, the caliber slides freely but was off when I checked it. I'm going to see if Carquest can turn it.

 

[73azbronco]

On BMWs, pulsing or vibrating brakes are 99 percent the result of poor bedding or contamination on the brake pad. Did you try driving it and getting on the brakes a few times from higher speeds to bed the brake pads? Bedding also loosens up the caliper rails. I club raced and even there with heavy braking, vibrating brakes was bedding or pad issues, not warped rotors.

The comment above about the caliper binding is key here, if you could imagine your rotor way out of spec, but the caliper could grab the rotor and easily slide back and fourth, you would have minimal vibration. However, add that small rotor variation into a brake that has caliper rails that bind, and you have vibration.

 

[larryejoh]

My caliber is free. I have a .010 wobble measured with my dial indicator. It was .005 before I turned it.

 

[SHOBRONCO]

rotor

You may consider turning the rotors with an on car brake lathe, like a Pro-Cut.