Not to be disagreeable or anything, but this isn't quite right. Braking force from the wheel to the fork is applied at the DO, not at the caliper. The caliper "pulls" backwards on the rim, and so does the road acting on the tire. If you want to decelerate at any particular rate, their total must equal that required amount force which then pushes backwards on the fork at the DO. The total torque required from the caliper can be lower if the rim has a larger diameter, but that doesn't change how much total force you need to stop. Or not stop, if you are unlucky.