Friday, March 12, 2010

Single Speed Coaster Hub Basics

A coaster hub is a single speed bicycle hub that allows the pilot to apply brakes by pedaling in reverse. This elegant simplicity makes the coaster hub great for non-racing type bicycles such as cruisers, cargo haulers and choppers. Because there are no derailleur or caliper brakes on a coaster bike, there are also no cables or levers, just a chain connecting the front and rear chain rings.

Coaster hubs can also be hacked into mid drive systems, allowing brakes on the axle of a trike or cargo vehicle by welding a sprocket to the steel shell. Coaster hubs are almost indestructible, so if you ever encounter a non-working unit, it may just need to be taken apart and regreased. So, let's have a look inside and see how this marvel of simplicity works.

A typical coaster hub wheel
Figure 1 - A typical coaster hub wheel

A coaster brake hub is very easy to identify since it will have only a single chain ring (sprocket) on the right and a supporting torque arm on the left. These hubs are found on the smallest of kids bikes right up to full sized beach cruisers and cargo bikes. Coaster hubs lack the ability to have more than one speed, but they do offer reliable braking and simplicity. Figure 1 shows a typical coaster brake hub on a discarded 16 inch kids bike wheel. Besides the number of spoke holes, most coaster hubs are of similar quality and functionality. Made of all steel, new spoke holes are easily drilled, and other parts can be welded to the hub shell to make unique transmission systems for your own projects.

A homebrew spoke screwdriver
Figure 2 - A homebrew spoke screwdriver

Any suitable flathead screwdriver can be used to remove the spokes if you plan to extract the coaster hub. To make your job easier, grind a small groove out of the center of a screwdriver as shown in Figure 2. It will now be a spoke removing screwdriver that can lock into place when the spoke extends past the spoke head. If you do not care to salvage the spokes or rim, just use a grinder and zip disc to rip through the spokes rather than spend all the time to remove them individually. Large wire cutters can also slice through spokes.

Removing spokes in sequence
Figure 3 - Removing spokes in sequence

If you plan to salvage the rim, spokes need to be removed a little bit at a time or you will bend the rim. Turn each spoke no more than one turn in the counter clockwise direction as shown in Figure 3, working around the rim from the valve hole. If you try to fully remove one spoke at a time, the tension will warp the rim after two or three spokes, and the damage may be permanent.

More of this free DIY and other how-to tutorials at .