Drum vs Disc, Power vs non Power

Mattax said

It is very important that the coefficient of friction is very consistant throughout the operating temperature range. If the friction goes down as the brakes get hotter, then the self assisting action becomes less. When this happens the driver has to harder and harder as the brakes work less well. .

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The opposite effects of changes in friction characteristics was a big big problem for some of the early stuff such as Velvetouch which was incorrectly suggested to folks in the late 60's early 70's. A good friend got sucked into this stuff for his 70 Chev K20. You'd be on the highway/ freeway, thundering along, brakes cool, and need to stop for some jam-up ahead.

You'd mash on the pedal and LITTLE would happen, until the damn lining started to warm up, and suddenly you'd be trying to "back out" of the pedal as they warmed up and started to work. Severe drum wear was another factor with that stuff.