It doesn't take a large change in the lever arm to make a significant improvement in braking force. As pointed out, the larger rotor will give the caliper a larger lever arm, which multiplies the braking force. It also adds a larger swept area on the rotor, which will dissipate heat faster and spread the energy of braking over a larger area to begin with (heats up slower).
There are also two different calipers, '73-'75 A-bodies used a single piston caliper with a 2.6" piston, 73+ B/E's used 2.75" calipers, so did '76 A bodies. The larger piston diameter in the caliper also increases braking force.
View attachment 1716059334
If you do the math on the braking force, just going from a 10.98" rotor to an 11.75" rotor with the same exact caliper results in an ~8% increase in overall braking force. The actual numbers are less important than the percentage, the math assumes 100% of the force generated at the caliper is transferred to the rotor which is not the case. But since we're comparing the same calipers, the percentage change should be the same. And on that note I used the same pedal force, master cylinder diameter, and wheel diameter for all the calculations, since all of those things change the total force number.
If you currently have 2.6" piston calipers, and you go from 10.98" rotors to 11.75" rotors with 2.75" piston calipers, the difference in braking force is ~21%. That's massive!!! And this is just the change in braking force, it doesn't even consider the heat dissipation and temperature differences.
And really, even a small percentage increase in the braking force can make a big difference. If your stopping distance changes by a few feet, what's that worth? Well, if it means stopping a few feet short or hitting something, it could be worth a lot.
I've run the 10.98" and 11.75 rotors on my Duster and my Challenger. The 11.75's make a noticeable difference, especially as you start to push the car a little harder. Now, I will say tires also make a big difference, and running 275's on the front of both of those cars I wouldn't use anything less than the 11.75's, that width of tire works the 11.75's pretty hard. If you're going to run 195's up front it will not make as much of a difference when you start translating braking force to stopping distance. Obviously the better your tires are the more important the larger brakes can be.
