ITS ALL ABOUT LEVERAGE as well as heat dissipation. Agreed, never argued
As for the rpm reference is comes down diameter. Sure rpm is rpm, but what changes is the fact 10 rpm of a 140mm is not the same as 10rpm of a 180mm rotor... this is most obvious in tire sizes, and the physics are exactly the same.
That was my point - the surface of the rotor is traveling under the pads faster with a larger rotor, and the pads sweep over more surface area with a larger rotor.
Larger rotor more stopping leverage. More leverage means you stop better and sooner. Stopping sooner means less time mashing the brakes... WHICH MEANS LESS PAD WEAR. Agreed to about the leverage. The pad material and/or the surface condition/material of the pad may not work with the increased swept area of the rotor, or the extra speed that the surface area passes under the pads, causing accelerated pad wear. I'm only suggesting that this is a possibility which depends on the composition of the pads.
It's all relative physics. YUP
Larger calipers and pads cover more rotor area NOT the other way around because a 1" wide by 1/2" tall pad is only going to cover that amount of rotor whether the rotor is 140mm or a 140 inches so physical rotor size is completely irrelevant in that respect, provided the caliper can handle the given size rotor. I never mentioned changing the size of the pads - only that the pads see more swept area on a larger rotor. It doesn't matter what size a given pad is - it will still sweep across more surface area at a faster speed on a larger rotor.
As for pad longevity, sintered ceramic seems to do the best for wear, but at the price if initial bite (they bite best after they heat up a bit) in my experience... and any type of organic and/or resin based ones tend to stop the best across all temp ranges but wear the fastest and have the worst wet performance It is true that different pad compositions have different wear and performance characteristics.
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I was bored and made a chart as to the difference in the swept area between a 6" and a 7" rotor, along with the
speed (in feet per minute) of the center of each at 300 RPM, or about 17MPH on a 19" tire. "Relative physics" will dictate how the end result of increased leverage against increased surface area scrubbed by the pads will affect pad life - the "relative" part being if that particular pads braking material can take advantage of the increased leverage and accept being worked at higher speeds and longer distances, and do so at the same wear rate.
This is turning into typing practice and we probably won't agree on the outcome.
Rotor size is only 1 slice of the pad wear pie - others include pad composition, apply pressures, weight, speed,
riding habits, etc. also determine pad life. Given the Asian nature of the market you may buy 5 "direct fit" sets of
pads for the same calipers and get 5 different results.
Hope the O/P enjoys his toy.
No honestly, I'm not riding the brakes all the time.
