Third time try at getting this on the list. Apologies for any duplication....
I think there's a simpler reason that the others presented here. Torque. To
stop a faster car in the same distance, you have to apply more torque to the
wheels. Torque is given by:
T = r x F
where r is the distance from the axis of rotation and F is the force (both
vectors), and x is the cross product (which reduces to simple multiplication
here). So to get a higher T with the same pedal effort you can either
increase F by using pads with a higher coefficient of friction, or increase r
by increasing the size of the pads and rotor. There are physical or functional
limits to the coefficient of friction, so increasing r is the only option for
high performance brakes.
Of course, larger pads and rotors will have greater heat capacity thus
operating cooler than otherwise, but I think this is a secondary requirement.
Rod Anderson
----- Original Message ----
From: Dr L. Kevin McNelis kmcnelis@nmsu.edu
OK, let me start by saying I AIN"T NO ENGINEER, and there are lots of
things about my LBC that I don't understand.
Why do those who build their cars for racing applications go for larger
brake rotors? I undertand the vented and cross-drilled, allows for
faster cooling of the rotor, prevents brake fade under hard use. But
why larger (i.e. greater diameter) rotors? Same reason? Larger mass
to absorb more heat, to prevent fade? It seems to me that if you have
a big enough rotor to lock up the wheels/tires, you have enough brakes!
Do the larger rotors help under repeated braking situations?
Thanks, and yes, I'm ignorant. That's why I asked.
Kevin
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