|BMW Z4 35 is front rotor (note: aluminum hat)|
I found through looking at OEM parts online that the Z4 35is has the same 348mm diameter equipped front rotors as the 335 only they have a full aluminum hat vs. the steel 335 ones. The main advantages of these over the stock rotors are:
1) Weight savings of 2lbs per corner
2) Rust free
3) Semi - floating disc has better heat dissipation properties
Ultimately given the additional $100(per pair) over stock OEM rotors I jumped all over them and have to say I am completely satisfied. The quality is typical OEM BMW and they look great under the rims even after 5,000 km. I can't say that I specifically noticed the reduction in un-sprung mass but when combined with the removal of the runflat tires the car feels more nimble and is another step towards my 100lb weight reduction goal (without removing any critical systems or affecting comfort and function).
|Z4 35is rotors installed|
For the marginal increase in cost this is a must have for anyone looking to lighten up their un-sprung mass, improving brake function through cooling and improving the aesthetics