Quote:
Originally Posted by BlackJetE90
The current M2 contradicts a lot of the arguments about correct brake booster. As we do know the current M2(with the standard M4 brakes) uses the M4 CCB brake booster. My suspicion is the 2NH accessory (red calipers) will not come with a brake booster for current M2 owners, as they already have the CCB part number. If true M4 CCB owners theoretically will be able to use the iron rotors. Brake boosters is usually more correlated to caliper and piston size, rather than rotor type. The CCB conversion kit has a upgraded brake booster because of the caliper upgrade, it needs more force for increased piston count/size. M2 basically has an overkill brake booster for the blue standard brakes. M3/M4 owners with standard blue brakes, will be the ones that need a CCB brake booster for either 2NH or CCB conversion.
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The brake booster unit difference is to compensate for the higher friction coefficient of the CC rotors according to BMW OEM documentation. Note that the F10 M5 uses the same front/rear calipers regardless of CCB/iron rotors (CCB rotors are 10mm bigger in diameter which a bigger pad size takes care of), however the brake booster is different. So the rotor composition is the difference, not the calipers or piston count.
Which means that BMW found something about brake boost/balance in the M2 particular chassis that required a
less potent booster than in the M3/M4 with the same exact iron rotors and 4/2-piston calipers brakes.