Disc brakes temperatures

MrWizard wrote:

JRscooby wrote:
I can't say what temps to expect but unlike drum shoes, the disc pads rub all the time not just when brakes are applied.

I did a Google check on that very topic because a friend of mine thinks like you do, and I think differently, I think there is suppose to be an air gap
Pads that touch mean friction and drag, they will wear more, wear it faster, and get hotter,

What I found was the statement and drawings, that when brake pressure is removed the bellows style piston cover retracts the piston and disc/rotor "run out" forces the pads away from the surface allowing for an air gap between pad and rotor, no value was given for the size of the gap

They do not touch when wheels are turning aka driving down the road

Think about this
A tire with a 4ft circumference will spin 1300 times in one mile, if you are driving 60mph that tire is spinning at 1300 rpm , if a brake pad is touching the disc rotor, it and the rotor are going to get hot, that is what friction does, brake pads have lots of friction capability or your vehicle would not stop

Go to a car race at night and it might make you rethink or every car out there is not set up right. I also think there is a gap " very small" but seeing them glow is another story. I have pulled brake pad off right after driving and you must have good gloves on to take them off. But I agree with you on the gap. I try to get runout to .002 or zero if I can. You will know it when they go out of round. Vehicles with a good brake job will not build up of rust or other stuff on the rotor due to the very low runout. They shine. Remember they are floating calipers.