I am trying to understand how and why a switch from a 12 inch setup to the 13 inch setup would provide a gain.
If the larger rotor provides more leverage but the smaller caliper size isn't as effective, why wouldn't they increase the caliper size ? Is there so much gain in the leverage that it greatly offsets the loss from a smaller caliper?
You are mixing and matching parts so there is no logic to the question. If you look at a late model car with 13 inch rotors you'll see that the MC bore size and the piston caliper sizes are all on the small size. The engineers figured out a few years back that if everything was smaller then it could all be lighter but still provide the clamping forces required to stop the car. The old 2.75 caliper used by Mopar back in the 70's doesn't really exist anymore. Now everything uses multiple pistons and small bore sizes.
