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      06-04-2012, 04:17 PM   #6
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Drives: 2004 BMW M3
Join Date: May 2012
Location: Midwest

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Originally Posted by r53s65e90 View Post
What you are asking is possible. With the use of larger pistons you WILL increase brake torque. However, you will also increase pedal travel if you keep the same master cylinder as you will need to displace more fluid. Hence, there is a tradeoff here.
This is absolutely correct.

Do you happen to know the width of the brake pads, front and rear?

I believe I came up with 65mm - based on that, I am getting a slightly higher bias of 1.77:1 for an OEM configuration based on those width estimates, though I am only basing those on the measured braking surface of the E9x rotors.

I built a massive spreadsheet containing a worksheet of front caliper/rotor combinations, and one of rear caliper/rotor combinations, then a cross between the two in another worksheet that gives any given bias for any given combination of F/R caliper/rotor combination.

This spreadsheet is for the E46 M3 and its variant packages, but should work just fine for anything you'd want to plug in if you have more numbers. It really is interesting to see how certain brake kit combinations could produce an astonishingly dangerous rear bias.