This is mostly a post for folks to stumble upon when searching through the archives someday...

I've had a vibration coming through the steering wheel whenever I apply the brakes at 55mph and higher. Right, right, front brake rotors, but that's not the case. I replaced my front rotors and pads, got new tires, and an alignment, yet the vibration persisted. I took the car to the dealer since it's still under the CPO warranty, expecting a faulty control arm bushing or something similar. To my surprise, the culprit was actually the rear rotors having excessive run-out.

I've never had warped rear rotors cause similar symptoms that would be experienced with warped fronts. I'm assuming that because the R56 is so stiff, in addition to being a small chassis in general, the transfer of energy from one side of the car to the other is pretty unimpeded.

TLDR; don't rule out the rear rotors when troubleshooting a vibrating steering wheel when braking.

 

I'm amazed you were able to warp the rear rotors. Drive for some time with the e-brake on? I'm convinced the rear brakes on these cars are just there for looks

 

Nope. We bought the car as a CPO two years ago and it always had that vibration. I just assumed it was the front brakes, and since brakes weren't covered under the warranty, I just opted to deal with it until the front brakes needed replacement. That time finally came two weeks ago, but after replacing them, the problem still existed (though to a slightly lesser degree). I usually replace all four corners at the same time, but for whatever reason, the rears still have a lot of pad life and rotor material remaining. New rear rotors are on the way.

 

I'm guessing the previous owners drove with the parking brake engaged at some point. The preexisting condition could have easily slipped past a CPO inspection that lacked the appropriate rigor.