Originally Posted by
sstorkel
As a layman, it sure looks to me like large rotors cause a bike to stop faster than smaller rotors. That would seem to suggest that there's more force (and thus more stress) involved somewhere between the brake caliper and the ground, wouldn't it?
Sort of, but not at every point in between.
When trying to stop a spinning disc, required force is reduced by a longer moment arm. Leverage. So a larger disc can stop a bike faster using the same force, or stop the bike the same using less force. (This is also why rim brakes work fine in most instances, even with less braking force, since they have the most leverage).
The end result of how quickly you stop is going to vary directly with the amount of stress on the hub, spokes and QR. The only thing that changes with disc size is the amount of force on the caliper (and by extension, fork) to achieve the same braking performance.
Larger discs, of course, make it easier to brake past your tire's limits, particularly in the rain.
This is high school physics stuff, I don't understand why there seems to be so much confusion about the forces involved.