Originally Posted by
London commuter
In any case, in determining the ratio of level force to braking force, the ratio of rotor radius to wheel radius (by simple Newtonian mechanics - think two levers fighting each other) matters more than absolute rotor size. For the same braking force, 700c wheels should have larger rotors than 26" wheels.
And the difference isn't huge. Less than the difference being in the tops or the drops. you don't hear anyone say "Don't ride in the drops or you'll do an endo if you brake".
The increase in radius is from 559 to 622, and the torque curve is linear - about 10% decrease in leverage all else the same.
26" wheel w/ 160mm rotor ~ 700c wheel w/ 176mm rotor. Of course, if you're locking up the wheel on the 26" bicycle already then you're probably fine.