resurfacing cross-drilled rotors?

[X5Guy70]

Does anyone know if the oem brembo replacement front rotors, which are now slightly warped, can be turned or resurfaced? BavAuto reccomends against it but I wonder?

Thank You,

X5Guy70

[mrbmwx5]

Yes it can be , just depends how thick or thin the rotors are.... I had my turned and it works great again.

[admranger]

How do you know that they are warped? Have you measured runout? If not, it is more than likely pad deposits or, perhaps, thrust arm bushings going out.

Tell us the symptoms please...

[X5Guy70]

Whenever I brake the front end pulsates and you feel it in the steering wheel and pedal....more at highway speeds but less pronounced stopping at a traffic light. Should one change the pads as well after resurfacing rotors? They are both relatively new.

[FSETH]

Warped rotors are not a common occurrence. In nearly all cases of brake judder/pulsation, the cause is pad deposits on the rotor. You can take them off and have them turned as long as they are in spec or you can put a more aggressive pad on and drive it hard for a while. TireRack says some drilled/slotted rotors may not be able to be turned. Not exactly sure which ones they are referring to.

If it were me, I would probably buy new pads and bed them in properly. If you do put the old pads on, be sure to bed them in again following Dave Z's recommendations. Just curious, how did you bed your current pads/rotors?

Here is what Dave Z says about brake judder/pulsation...

The obvious question now is "is there a "cure" for discs with uneven friction material deposits?" The answer is a conditional yes. If the vibration has just started, the chances are that the temperature has never reached the point where cementite begins to form. In this case, simply fitting a set of good "semi-metallic" pads and using them hard (after bedding) may well remove the deposits and restore the system to normal operation but with upgraded pads. If only a small amount of material has been transferred i.e. if the vibration is just starting, vigorous scrubbing with garnet paper may remove the deposit. As many deposits are not visible, scrub the entire friction surfaces thoroughly. Do not use regular sand paper or emery cloth as the aluminum oxide abrasive material will permeate the cast iron surface and make the condition worse. Do not bead blast or sand blast the discs for the same reason.

The only fix for extensive uneven deposits involves dismounting the discs and having them Blanchard ground - not expensive, but inconvenient at best. A newly ground disc will require the same sort of bedding in process as a new disc. The trouble with this procedure is that if the grinding does not remove all of the cementite inclusions, as the disc wears the hard cementite will stand proud of the relatively soft disc and the thermal spiral starts over again. Unfortunately, the cementite is invisible to the naked eye.

As others have said, check the thrust arm bushings as well to be sure that the issue is actually the brakes.

The following StopTech link was from Zeckhausen's website. There you will find many links to FAQ's regarding bedding procedures and judder.

StopTech : Balanced Brake Upgrades

Also, one last thing. Brembo cross drilled rotors are not OEM. They are aftermarket. For the most part, replacement drilled/slotted rotors are pretty much wheel jewelry and do not give any performance advantage.

[admranger]

When's the last time your thrust arm bushings were replaced (hint, hint)?