Over time the bearings in the hubs of a bicycle wheel may come out of adjustment causing the wheel to wobble from side to side (this can also be the result of the wheel being out of true; a sure sign of loose bearings is that the rim can be moved laterally in the fork by hand). Additionally, road dirt and moisture infiltrate the bearings, causing rough operation and premature wear. Even if these issues do not arise, the bearings’ lubrication will eventually need to be replaced in order to maintain the life and health of the hubs. These problems can be addressed by overhauling the hubs. The basic techniques are similar to maintaining any other ball bearing assemblies, whether the headset or bottom bracket on the bike, or on complete different applications.
On some recent model mountain bikes, there has been a rash of rear hubs getting significant play after only a few rides; this may be due to bad cones or lock nuts. The drive side lock nut should be your number one suspect in this case if the bike is new.
Parts of the hub
From the inside out:
- Bearing cup
- Bearing cone
- Dust cover
- Lock washer
- Lock nut
- Quick release skewer
Main body of hub, holds the axle assembly and is the connection point for the spokes.
Is pressed into the shell.
Forms the outside bearing races, fits onto axle, usually adjustable.
There are three major types of bearings in use on bicycle hubs:
Cup and Cone types
- Loose ball bearings are placed individually in the bearing race
- Caged bearings are simply loose ball bearings held in a framework, which simplifies their insertion in the hub. They differ from sealed, or cartridge, bearings in that the bearings are visible in a simple cage made of a circular piece of sheet metal with holes punched for the bearings, and the bearings can be inserted and replaced into the cage with simple hand tools, or even just with the fingers. Cup and cone bearing hubs also usually have some form of sealing but it is separate to the bearings.
- Cartridge bearings are assembled and sealed in a permanently pressed housing which renders them inaccessible. Cartridge bearings which are sealed have the advantage of being highly effective at preventing dust and moisture from entering bearing housing and usually need no adjustment. They will generally last many years without service. If they do fail, they are simply replaced. Some hubs cannot be disassembled when the cartridge bearings are worn or fail; the more expensive ones can sometimes be serviced by the manufacturer…
Cleaning and repacking a traditional cone and cup front hub
- Place the