[diamondnik]

Ok, long time ago I installed an e36 M3 master cylinder because I hated the squishy feel of the stock brake pedal, and I knew that I would upgrade my brakes at some point. Except that instead of M3 fronts (60mm piston) I installed e46 330 front brakes (57mm piston). I've been driving around like this for some time now and have mixed feelings about how well this arrangement works. I have larger rear calipers on the way (38mm piston) because I noticed that the rear just wasn't working well at all; pads and rotor would never really warm up and it was just causing galling on rotors (new rotors, brake lines and rebuilt calipers). Also, I don't think its normal to get over 100 000km out of same set of rotors and brakes...

So here is what I found regarding this. The M3 master cylinder is stepped; it's ID is 25.40 Front and 20.64 Rear, while on the TI it is 23.81 F/R. I looked at the 330 master and it is also stepped (23.81/22.20). So I looked into this reason, and figured that it must have something to do with ATC or DSC (on e46+). For this reason rear lines have different pressure, presumably to soften/dull line pressure when traction control kicks in. And since my Ti doesn't have traction control, I don't need a stepped master cylinder? And was the reason I got so much life out of my rotors and pads because rear was 20.64 ID?

So to recap:

e36 M3 60/40 caliper pistons and 25.40/20.64 MC
e36 Ti 54/34 caliper pistons and 23.81/20.64 MC
e46 330 57/44 caliper pistons and 23/81/22.20 MC

I can see how the M3 needs a larger diameter MC for front pistons, given their size, but if the 330 is fine with 23.81 front ID, then maybe I need to switch back to my original Ti master cylinder. Another thing concerning 'feel' generated by MC sizing. Originally I wanted the larger MC to stiffen the pedal and give better feel, like what you'd get in a competition car without power assist. But I think that the large MC just gives, what we'd call in motorcycle circles 'wooden lever' feel, in other words, you need lots of force to push fluid and get same result that you'd get from smaller MC and less needed force (it also dulls feel of line pressure). The Ti MC would give a softer pedal and still same braking power. The thing is, I can't even remember what the original Ti brake pedal felt like. On my one motorcycle I found that original MC made braking a chore and I'd need 4 fingers to modulate brakes, while two fingers with smaller diameter MC. I wonder how things would feel with the original MC.... Any thoughts on this issue?