Originally Posted by
Salamandrine
Still, I wonder if there is some practical limit. For example would a pad 1/4 the normal area have the same drag? Perhaps increased pressure would mean increased temperature and change the friction of the pad? Or perhaps it would have the same braking power and it is just a matter of pad wear?
Yeah, the problem with classroom physics is that the things that were simplified away in order to get a manageable model are actually important once in a while. In this case I was imaging a brake pad the shape and size of a pencil eraser, and I'm fairly certain that the lateral flex would have some impact. So I guess you need enough pad material to maintain structural integrity. You may be right that temperature could also come into play (though probably not for a small difference like switching from road the MTB pads).
This issue also comes up with tires, which I think are more complicated because they deform a lot more. You just couldn't convince me that the size of the contact patch is never important in tire traction, especially over irregular road surfaces.