Chalo said:
speedmd said:
Stainless in general is a slippery material ( I deal with several grades daily ) and may be just a poor choice for ultimate performance and mainly used for cosmetic considerations.
It's true that my best motorcycle disc brakes were some kind of carbon steel, made by EBC. They were better than stock in pretty much every regard I can think of.
Stainless alloys seem to tolerate surface wear relatively well; not as well as bearing bronze but better than plain steel. I'd be willing to try Ampco bronze or similar for disc rotors (expensive, but wear resistant and thermally more interesting than stainless). I've wanted to try that for a coaster brake hub shell for a long time.
I've never come across M2 high speed steel in any other state than glass hard, even after getting red hot in an ugly machining scenario. But I suppose that it's steel after all and thus can be annealed to some degree or another.
Well proven materials automotive and motorcycle industries have typically been cast iron,... strong, holds it's shape well at glowing hot temps, good wear resistance (even at those hot temps), but it's brittleness and low corrosion resistance is a huge liability in the thin forms of current exposed bicycle disk designs.
Carbon steels would certainly be better than cast for thin steel disks, depending on the crystalline structure and designed controls of expansion that causes deformation under stresses of high heat,.... and corrosion resistance lacks a bit.
The "self-healing" slippery qualities of stainless alloys and Aluminum/bronze such as the various Ampco materials is indeed desirable, but I'm not so sure they are even close in comparability in that thin disk design, where stainless will certainly excel.
As I was about to post this, I notice speedmd posted with further considerations of high speed steel and various stainless alloys, (and problems thru out the day tryin' to get back to this) as well as the post above by liveforphysics, and I wholeheartedly agree with both! I do think some of the 430 alloys would be excellent, as would the better 440 series,... with proper brake pad compounds of course. You do have to consider the designed system as whole. I probably wouldn't be so fond of costs in such products, but they'd likely be much less than other exotics above, and I'd luv to try a few!