coaster brake , basic question
 

why are brake shoes needed inside the hub? the driver presses itself a against the hub shell to move the bike forward when pedaled. but it presses shoes into the hub shell to stop bike. why not just have driver press into the shell itself... what do the shoes do that it cant? dissipate heat?

The clutch (driver) needs much less friction than the brake shoes. It's a game of surface area. Yes, heat capacity has something to do with it, but not a whole lot (modern shoes are quite small compared to vintage models).

And to the well said post above, one wants a bit of free play between on and off functions. As my first car mechanic said after he rebuilt my brake, "you don't want a wall switch for brakes". The slight bit of slop between the clutch/shoes and hub shell give you this.


As an aside-I worked on my first coaster brake after overhauling a number of SA AWs (and a S3C too). I remember looking at it and wondered aloud what to do. My boss said it had about a dozen parts (compare to the SAs with MANY more). And why was I hesitant.


Second aside- As to heat capacity goes just ask the Repack riders about that. Andy

Heat is dissipated by burning the Grease..

Because the brake would always be engaged, even when pedaling forward.

they are very mysterious until you dig in. not like rim brakes where you can see how it works.

thanks for all the responses