Cartridge bearings are an evolution of cup-and-cone bearings, where the ball bearings sit inside a sealed unit rather than directly against the hub internals.

Like cup and cone bearings, the ball bearings in a cartridge unit will usually sit inside a cage to maintain equal spacing and will be packed with grease.

Cartridge bearings will feature an inner and outer race – equivalent to the cup and the cone – and a rubber seal on the inner and outer faces.

These sealed units are designed to fit tightly inside the hub to prevent the whole cartridge from moving rather than just the internal loose bearings and, as such, should ideally be pressed in with a bearing kit to prevent damage.

Cartridge bearings are not adjustable and are replaced as a complete unit when they wear out.