Brucey wrote:at 'normal speeds' dragging the brakes all the way down usually results in higher brake temperatures. This happens for two reasons;
1) the net heat input to the brakes is higher (less potential energy is spent working against air resistance) and
2) the cooling rate of the heated parts goes approximately as the square of the speed, but the heat input goes approximately as the speed.
However this isn't the full story; the cooling rate isn't quite zero even at zero airspeed, so at some (very low) speed the brakes will start to run cooler again. Quite where this will happen speed-wise will vary with the bike, rider and the steepness of the hill etc. But to a first approximation this is likely to vary with the surface area of the hot parts, so again small wheels will suffer worst.
It wouldn't surprise me to find that this 'ride slow=cool brakes' thing needs speeds around walking pace in some cases, i.e. impractially slow.
Looking at what Thorn say, I think that for small wheels that is probably right. Have a look at their Links. Graphs and everything.
Motorcyclists can get their exhausts plasma sprayed with heat shield stuff. Now if we could do that with the inside of wheel rims...