Originally Posted by
bendembroski
Interestingly, I have noticed that rim-wear due to braking seems to happen more quickly when compared to 26" or 700c wheels. but that could be down to a bunch of other factors (For some reason, the little wheeled bikes always seem to be out in the rain more, for instance).
You are spreading the (approximately) equal braking energy over less area: Does it take longer to sand a small end table, or a large dining table? Because the tires are about the same profile, but the rim diameter is smaller, the smaller wheel also has a little more leverage at the brake pad, so you need a bit higher force. (the "brake disk" is a little smaller in relation to the outside diameter of the wheel)
Force at brake pad= force at tire * [(BSD +2*tire width)/BSD]
(assumes round tire section)