Rotor size doesn't matter. Rotors do not stop cars, tires do; you can't slow the car quicker than the tire will let you.

LouisM if you are strictly talking stopping distance on the street, none of those things will really do much. As I pointed out, once the tires are near locking there's nothing else the brake system can do.

Check our link list: Everything you ever wanted to know about brakes but were afraid to ask by Grassroots Motorsports

Brakes are hydraulic and therefore are capable of clamping the friction material ENORMOUSLY hard. Yes a bigger rotor could get by with less clamping force to give the same decel of the tire. But nothing is free. The larger rotor must have more friction material and more piston area to clamp it. If not, the larger rotor will merely heat the pad material every bit as quickly as the smaller one. Since the larger caliper has larger pistons and since it is hydraulic you have to displace more fluid. So you either press the pedal further or use a larger piston on the master cylinder which means you have to push the pedal harder. The pistons at the rotor may be doing less work, but the one in the master (along with your foot), is doing more work. Hydraulics obey the conservation of energy laws just as levers and gears do. Nothing is free. Your fan example obeys the same laws. The fan may be easier for you to stop by grasping it at its outside, but the fan tips will travel farther here than at the inner end since the outer circumference is larger than the inner one. The work to stop the fan is the same whether you grasp is at its inner or outer circumference due to the definition of work (force x displacement). Stopping the fan at the middle requires more force, but less displacement. Stopping the fan at the outside requires less force, but more displacement. Think about the fan's rotation. In order to stop the fan you must deplete all of its kinetic energy. How you choose to stop the fan makes no difference, you still have to absorb the same amount of kinetic energy.

In the scheme of things (stopping distance) larger rotors have practically no impact, they are not used because of superior mechanical advantage. This can be verified (as thousands have) rather easily by measuring stopping distances on different sized rotors with everything else remaining the same. The 17% difference in your 4Runner example I bet has more to do with ABS software tuning or test variables than rotor size. The only exception would be that if the friction material is woefully inadequate and incapable of good performance. A larger rotor may help there.

Go do one 100 mph on "small" rotors and punch the brake pedal as hard as you can. You'll lock the tires nearly instantly. Now go do 100 mph on "big" rotors and punch the brake pedal as hard as you can. You'll lock the tires nearly instantly. How did the bigger rotor improve your stopping distance? It didn't. Stopping distance was the same in both cases. A brake merely needs to be powerful enough to stop the tire.

The bigger rotor will not stop the tire quicker; once the tire locks everything else doesn't matter. Larger rotors do not make tires lock quicker than smaller ones.