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Originally Posted by berj
I may be mistaken.. but I've always heard that cross-drilling was all about weight. Is that not a factor in the decision for cross drilling?
Sorry about the thread-jack.. but I thought this a good a place as any to ask.
Berj
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Hi,
Certainly when you take away material as when drilling the rotors, you are removing Mass (weight), but you'll remove maybe 10%, any more and the integrity of the rotor is lost, not to mention that the loss of Mass also impedes the heat transfer, which is really all braking is - the conversion of inertia (stored energy) and mechanical energy into heat energy which is then vented to atmosphere and removed from the
system. Motive force (the car's energy) is reduced to a point below that of the Resistive Force ( rolling resistance, and aerodynamic drag) acting on the car, and the car slows or stops.
But, the reason for cross-drilled rotors is that when a brake pad is pressed hard against a rotor, a plasma builds from the pad material which is burned away and lives between the pad and the rotor. This plasma reduces the pad-to-rotor contact and consequently reduces braking efficiency.
By drilling holes in the rotor, you provide an escape for this plasma (many refer to this as Gas, but it really isn't) and assure better rotor-to-pad contact and more efficient braking.
But, for a street application, you simply don't work the brakes hard enough that it makes any difference. The brakes cool between applications and you're hauling down from 30MPH, not 130MPH, so not nearly as much plasma is produced in the first place. Hope this helps...
Happy Motoring!... Jim'99
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