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      06-05-2012, 02:50 AM   #8
r53s65e90's Avatar

Drives: r53 s65e90
Join Date: Mar 2009
Location: San Jose, CA

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Originally Posted by p0lar View Post

Do you happen to know the width of the brake pads, front and rear?
Check these out:

They are links from:

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.
Your calculations are more accurate. I just used rotor diameter instead of the more accurate rotor diameter minus 60mm which takes into account where the piston applies force. If you do this you get 60*60*300/(46*46*290)=1.76. I was just interested in ballpark numbers to start with. Once I have the real piston sizes I can go fancy.

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.
This sounds nice. Can you share?

Last edited by r53s65e90; 06-05-2012 at 02:56 AM.