Here are MY musings on brakes for a lazy Friday morning. If y'all wanted a braking discussion, this should provide plenty of fodder...
Energy can neither be created nor destroyed; only converted.
This rather simple statement has far reaching implication when braking discussions take place, yet it seems to get overlooked time and again.
While the kinetic energy in a moving car must be converted to heat in order to stop that car, not all of the heat goes into the rotor (but that IS where we want it to go). Having said that...the only variable that we can generally control is the rotor to pad relationship. More brake pad to rotor pressure can overcome the leverage disadvantage of having a smaller rotor. In addition, more pressure can overcome the disadvantage of having cheap pads that don't "stop easy" or have a lower Coefficient of Friction.
Now, when we use these cheap pads and small rotors and we require more pressure to get the same amount of braking force, other parts of the system suffer. If, for instance, we were using a rotor/pad combination that required A LOT more pressure to stop the car because of size or because of a lower coefficient of friction between the pad and rotor(both mechanical disadvantages), then we end up boiling the brake fluid which makes it hard to apply the aforementioned extra pressure between the rotor and pad. A catch 22.
sidebar:
The brake fluid boils, not because of heat transfering from the rotor, but because it's under TREMENDOUS pressure. As anyone that has studied thermal and fluid dynamics can confirm, when you pressurize a fluid, it get hot. When you relieve that pressure, it cools.
/sidebar
A higher coefficient of friction in the pad to rotor relationship will force more heat into the rotor and less heat...elsewhere. So, in that sence...the dingbat on the other forum is right. Furthermore, a larger rotor allows for a larger contact patch and inherently(because of it's higher thermal mass), can absorb more heat...again...forcing more heat into the rotor allows you to avoid forcing it...elsewhere.
Eventually (hopefully after stopping your car several times), even the larger rotor will be too hot to maintain effective braking. Once that happens, the heat MUST go elsewhere. Incidently, it usually goes into converting the brake pad into a gas. This gas gets trapped between the rotor and pad, drastically reducing the amount of friction that the rotor sees....so we press harder on the pedal and were back to the aforementioned catch 22.
Is the rotors primary job to be a heat-sink?
YES.
I rather think of it as a heat sponge.
Pretend you had a dry sponge (a cool rotor) in the bottom of a frying pan and you dripped water (heat) on it at a constant rate. You should be able to drip water on it for a while...and then it will fill up and the water will have to go elsewhere. If you were to stop dripping water onto the sponge for a while, it would dry back out (cool down) as the water evaporates and you could continue dripping water on it. Remember, we want all the water to go directly into the sponge...not elsewhere.
Now, how can we increase the sponges ability to take a faster rate of drips?
A. replacing it with a larger sponge: This will help a little because there will be more surface area to allow for the water to evaporate. It will especially help in the beginning because it will take longer for the sponge to fill up...but the sponge will STILL fill up eventually if the rate of drips is faster than the rate of evaporation.
B. Apply heat to the sponge: This will help will make it dry out faster.
OK back to cars and brakes...
Since were not braking our cars at a constant rate and when we're NOT braking our cars at all, we're forcing more air over the rotor(by going faster in the straightaways). This relates to answer B. We are already taking advantage of answer B....A little ducting to force even more air over the rotor will help a lot, too.
So, were left to replace the sponge err...rotor with a larger one that can dissipate heat at a faster rate and we also have the ability to replace it with a Sham-WOW! (better pads with a higher coefficient of friction).
Have at it. I got work to do.
:theyareontome:
that was funny! Sorry Jason! 
