[SD ///M4]

Ok, realoem.com was right. All of the online retailers are wrong when they say that BMW p/n 34111123072 does not fit a Z4 M Roadster, and here's the proof.

p/n 34111123072 is the hold-down bolt for the front rotors and p/n 34211161806 is the hold-down bolt for the rear rotors. Both are M8x12 but they are distinctly different. The front rotor bolt is smaller in size and requires a 5mm Allen socket while the rear rotor hold-down bolt is larger and requires a 6mm Allen socket. In addition, the rear hold-down bolt will not fit inside the hole seat in the front rotor and does not fit flush with the surface of the rotor due to the additional "shoulder" on the bolt and the larger face.

Fortunately, all of the hold-down bolts came off easily with an impact driver after an application of Liquid Wrench. The front hold-down bolts were in pretty good shape, cleaned up pretty well, and can be re-used, while the rear hold-down bolts were quite rusted.

And yes, there are two hold-down bolts in each rotor.