These common “Falcon” brand coaster hubs have a tendency to let in water if left out in the rain, and as I am thinking of using a spare pair of salvaged 16″ wheels for a home made bike trailer, I decided to overhaul them just in case.
The steel rim had to be de-rusted on the inside then the hub disassembled, cleaned and re-greased. There is a good description of this process on the useful Park Tools site – suffice to say the most difficult part is reassembly as your hands quickly become covered in slippery grease if you get it wrong, and that makes it really hard to then hold the assembly together …
The brake arm, shoes, clutch and spring will only fit into the left side of this hub when held together as an assembly.
When the assembly is pushed home the spiral-threaded driver can then be screwed into the clutch from the right hand side of the hub, then the outer bearing, cone and locknut fitted.
Coaster brakes use this spiral threaded driver to engage with the spiral inner of a notched clutch – when pedalling forward the clutch wedges onto the inner hub to allow forward drive. When pedalling back the driver disengages then wedges the clutch into the brake shoes which expand out and slow the hub by friction. A return spring releases them again as back pedal pressure is eased – simple really ! Not so simple though are the internally geared coaster hubs ….
In my experience the first bearings to go dry are the small ring on the outside of the driver as they are most vulnerable to water, and the grease is washed out causing rust and pitting. Water can also flow through the driver down the axle to eventually rust the springs on the brake arm side. This was just starting to happen on this example.
The obvious lesson is that bikes really suffer if regularly left out in the weather, and then maintenance needs to be greatly increased to compensate if the bike is not to become a problem.