Disc rotor choice - theory vs. practice

[NHAero]

In theory, the surface area of the rotor doesn't matter. I have KCNC rotors on my bike, quite lightweight, wonder if people have experienced any effect of braking performance by choice of rotor, especially in a heavier rotor with more material in the braking area. I'm not riding where I have long steep hills where the brakes get too hot, I'm asking about general stopping performance and whether the rotor choice matters. The brakes I'm using are TRP Hylex and I have a 160mm front and 140mm rear. It's not hard to skid the rear, but I think I could have more stopping power on the front.

I understand that pad choice (I'm using the stock pads, some don't like them and switch to metallic pads) and rotor diameter matter.

[Buzz Killington]

I'm not answering your question here (maybe I am a little...) I have no evidence to back this up, but have been told that rotors often warp after a long descent and the rider keeps the brakes applied when stopped. The rotor where the pads are clamping the rotor cool at a slower rate than the rest of the rotor that's exposed. That variation in temp can cause warping. Engineer types please feel free to debunk. I went to college for business. And girls. And beer. Only had success with one of those.

[alembical]

No real clue.

However, I switched from Sram Centerline rotors to Shimano Freeza ice tech rotors and noticed a big improvement. Big caveat and reason likely is that I swtiched to the new organic pads at the same time. I would think the new pads made a larger difference. My understanding of the new rotors is that the design is primarily related to dealing with heat buildup and longevity, rather than stopping performance, which I personally think is more a pad issue. I have and also previously had, no issues with amount of braking power, but the feel increased... but likely due to pads, not rotor change.

[wallymann]

Braking "area" and "leverage" are big deteminants of absolute braking power. Along with the friction coefficient of the pads.

Area is established by the pads (number and size -> swept area).

Leverage is established by the rotor diameter.

Rotor surface area doesn't really matter to absolute power, but can affect ability to accept and buffer energy from extended braking. More area can improve cooling and implies more rotor mass (for a given thickness) to absorb more energy. Both can delay brake fade due to heat buildup.