Bicycle Coaster Brake Repair

The rear wheel hub is where the coaster brake internals reside.

According to the late bicycle authority Sheldon Brown, "there are differences in [coaster brake] detail, [but] all [single speed] coaster brakes are fundamentally similar." Bicycle coaster brake repair is usually a matter of disassembling, cleaning, lubricating and reassembling the coaster brake hub. Occasionally worn-out or broken parts will increase the difficulty of the job, especially if the hub is an old or an uncommon design. Using a high-quality waterproof bearing grease will give the best lubrication results in coaster brake applications. The most difficult part of the job is the final adjustment performed after reassembly, as bicycle hub bearing cone adjustment is a matter of trial and error, needing much patience.

Due to the extremely difficult nature of disassembling and reassembling multi-speed coaster brake hubs, only a trained bicycle mechanic with this experience should attempt such an endeavor. Luckily, single-speed coaster brake hubs are simply and easily repaired by consumers.

Things You'll Need

• Cone wrench appropriate for the hub cone wrench flats (typically a 15mm cone wrench, but there are many different possibilities on less common hubs)
• 10-inch adjustable wrench
• Flat-head screwdriver
• Waterproof-bearing grease
• Several clean cloths

Instructions

1. 

   Use a flat-head screwdriver.

   Remove the snap ring holding the sprocket to the driver, using the flat-head screwdriver to pry the ring loose.

2. 

   Use an adjustable wrench.

   Insert the cone wrench in the wrench flat on the hub cone opposite the driver--the non-drive side lock ring--and hold in position while loosening the axle locknut, turning the adjustable wrench counterclockwise. Remove locknut and brake arm entirely.

3. Remove cone and inspect for pitting or cracking in the surface. Replace if necessary.

4. Remove non-drive side bearings from the hub shell. Inspect and replace if necessary.

5. Slide axle assembly toward drive side and remove entire assembly. Inspect all surface for pitting and cracking. Replace if necessary (to remove parts from the axle if replacement is required, loosen drive-side locknut in the same fashion the non-drive side lock ring was loosened).

6. Remove drive-side bearings and brake shoes from the hub shell. Inspect all parts and replace if necessary.

7. Wipe all surfaces of all parts and the inside of the hub shell clean with a clean cloth.

8. Pack the inside of the hub shell with grease and coat all internal hub parts with grease. This includes the brake shoes.

9. Insert brake shoes and drive-side bearings in the hub shell.

10. Check tightness of the drive-side locknut with the cone wrench and adjustable wrench. Turn the adjustable wrench clockwise to tighten locknut firmly.

11. Insert axle assembly in the hub from the drive side.

12. Insert non-drive bearings in the hub shell.

13. Thread axle cone on axle and turn clockwise until cone surface contacts bearing surface.

14. Slide brake arm on axle and thread locknut clockwise until snug.

15. Turn the locknut with the adjustable wrench clockwise while steadying cone with cone wrench. Tighten firmly. Check the axle for slop--side-to-side movement--or over-tightness. Axle should spin freely in the hub shell without the hub rocking back and forth independent of the axle movement. The key is to get the cone and bearing contact at just the right pressure. Repeat step 15 until axle spins freely with no slop.

16. Install driver sprocket and snap ring, using the flat-head screwdriver as a lever on the snap ring.

Tips & Warnings

• Finding exotic or old coaster brake parts is exceptionally difficult, and replacing the entire wheel with a modern design having readily available parts may be a better option.

• Improper assembly could result in damage to the hub or injury to the cyclist. Consult the local bicycle shop if questions or concerns arise.

References

• Sheldon Brown: Bicycle Coaster Brakes