Since the torque stays constant, when you move from the effective radius to the rolling radius (radius gets larger), the force pushing back on the car gets smaller. If you increase the rolling radius, you will decrease the force acting on the car even more.
Well, for our example, shouldn't the effective radius also be constant? Wouldn't the only way to change that be to move the brake mounting points in or out?
In that case, r shouldn't be either Er or Rr because it wouldn't change anything if it was Er (you said Er = hub center to pad center, and that doesnt change with a bigger tire).
So, I am thinking it should it be something like: BF = (BT*ER)/DRR
Or maybe: BF = BT(ER-DRR)
(Braking Force, Braking Torqe, Effective Radius, Dynamic Rolling Radius)
We want overall breaking force over by itself since that's the important result of all of this discussion.
From what you've described, increasing ER = good so it should multiply or add to the Breaking Torque to enhance Breaking Force (maybe there is some validity to the big break kits, since bigger rotors would have a larger ER)?
On the other side, DRR increasing should reduce breaking force, so it's a reduction/divison/subtraction of the Breaking Torque.
I guess all I am really curious about is just how much of a difference does that make in comparison to changes in the rotating mass?
For example, if someone was to switch to a tire/wheel combo that is 7-9lbs lighter, but increases the DRR by a half inch... are they going to stop quicker? see no change? break slower?
Just for giggles, I thought I had a good analogy involving a big kid, a little kid and a see-saw (leverage), but my brain cant seem to wrap around the concepts enough to make it funny or to make it make sense.