[Surly73]

I won't get into a whole thing here, but carefully note that F10 factory rotors are two piece - aluminum hats and grey iron swept surface. All of the inexpensive options that come up when you search parts sites are one piece, all grey iron replacements at half the cost or less.

I prompted discussion earlier in the year on a forum somewhere or other about using 1 or 2 piece rotors when doing a DIY job. There is some indication that BMW may have "updated" the replacement part for the F10 to be one piece, while new cars continue to roll off the line with two piece. There is some discussion that maybe this change took place because maybe there are some longevity and vibration problems with the 2 piece design.

However, the part system supercession:

1/ did not come with a bulletin drawing attention to the design change
2/ is merely the elimination of the word "light weight", but the shipping weight listed is less than a kg different.

I am not positive that there is a BMW-originated design change to the part (e.g. no bulletin) at all and, if there was, I'm not sure whether it's a design improvement (e.g. to reduce vibration) or cost-saving/margin-increasing when servicing "old" cars. To my knowledge, newer cars are still equipped with the two-piece design so if it was a design issue then the newer cars would have been changed too.

ANYWAYS - I say all this just to point out not necessarily to argue that 2 piece is better but that apples must be compared to apples when questioning pricing. If the quoted rotor is a genuine BMW rotor it will almost certainly be the 2 piece one and more costly. I specifically sought out two piece and ended up with Pagid 2 piece high carbon rotors from ECS (currently $299 US free shipping for the pair of fronts, I think I paid $270, both of which are higher than your quote).

Quality OEMs like Zimmerman offer BOTH 1 and 2 piece designs (I have the Zimmerman part#s somewhere, which were given to me in this same other thread from earlier this year) but many shops like FCP, Rock auto etc... only choose to offer the one piece.