yeah I've done big brake upgrades on light cars before mainly fords but its normally big heavy wheels that normally effects handling anyway was just a thought as callipers do weigh alot. I'm sure the pre facelift is still lightest Z4 and facelift was abit heavier which is why it needed 30+bhp more hence bigger brakes and is only 0.2s quicker. I've really never found the smaller brakes a problem stopping on road or track but aesthetically it does look worse. My old 330ci brakes seem huge now looking at the z4 ones I'm sure they was 325mm or 300mm I cant remember never really bother looking into size on my z4 as I knew they looked smaller