Cup and Cone Bearings

Most moving bike parts use cup and cone bearings. This means there are ball bearings sandwiched between 2 angled surfaces which rotate against each other. In this post I'll demonstrate how these bearing pieces fit together. First is the headset:

The headset bearings allow the fork and handlebars to pivot freely against the frame. Here is a threaded headset disassembled:

The frame cups are pressed tightly into the frame's head tube, and the crown race is pressed onto the fork. The top race screws onto the fork's steerer tube to preload the bearings, and the adjustment is secured by the top nut (which also screws onto the steerer tube). There is usually a keyed washer between the top nut and the top race to prevent the headset from loosening.

Next is the bottom bracket:

This bearing allows the cranks to spin freely, and also supports the rider's weight while standing. Shown here is an adjustable English bottom bracket with a square tapered spindle:

Both cups screw into the bottom bracket shell on the bike's frame. The fixed cup is tightly secured on the right side, while the adjustable cup in only screwed in enough to preload the bearings. The lockring threads onto the outside of the adjustable cup to secure the adjustment. The cranks attach to the spindle, which is meant to turn freely inside the bike's frame.

The last bearing I'll show here is the wheel hub bearing. These bearings allow the wheel to rotate freely, and support the rider's weight. Shown here is a rear freewheel hub:

The bearing cups are pressed into the hub shell, and the cones are screwed onto the axle. The ball bearings rotate between these two surfaces, allowing the wheel to rotate freely. The bearing's adjustment is secured by a locknut next to each cone. Here is the hub disassembled:

 

In general, a good cup and cone bearing will last a very long time. You can dramatically extend the life of these bearings by disassembling them, cleaning the bearing surfaces, and reassembling them with fresh grease every few years. The reason to do this is to remove contaminants from the bearings and prevent premature wear from abrasive particles. Additionally on a very old, neglected bike the grease likely has dried up and will need to be replenished to protect the bearings. The type of grease you use doesn't matter very much since bike bearings don't get hot or spin at thousands of RPM. It's best to use whatever is on sale at your local hardware or auto parts store. Automotive wheel bearing grease and marine bearing grease are especially good choices because they are water resistant and typically have extreme pressure additives to protect the bearings against shock.