Disc sizing ???

[mitch_04]

Well, I'm no expert but I try to listen to them!

First off, you want to figure out why larger rotors are "better". The larger rotors has 2 main benefits. The first, and probably most important, is increased mass. A larger rotor has more mass so it will take more &/or harder braking before it will heat up. This is assuming identical rotors except for diameter.

Second, leverage. A longer lever creates more torque, as anyone with a cheater on a breaker bar knows. The further away from center the pads are, the more leverage it will have to stop the spinning rotor.

The downsides to larger rotors is weight and packaging. The extra mass that keeps it from heating up also makes it harder to start when it's stopped and harder to stop once it's spinning. Just like heavier wheels, or any heavier spinning piece in the drivetrain, it robs acceleration. I can't remember the exact amount, but any extra weight that spins has double or triple or whatever the effect due to the rotation. Packaging is pretty self explanatory, gotta have room for the brakes!


So as far as your question goes...well... same size brakes or bigger in front will both work. Having a properly designed hydraulic system to apply the correct pressure at the wheels is more important, think of rotor size more as "endurance" than actually helping you slow more quickly...although they are related.

Ron Sutton has mentioned in one of his threads that he uses a relatively small rotor (11" or 12") in some of his race cars and it does just fine. You just need to figure out what exactly you are trying to accomplish with your build, and figure out what will meet your requirements best!