Wheel Bearing And Bottom Bracket Maintenance

by Amy Garrett

Does your bike not ride as smooth as it once did? Do you hear a grinding sound coming from the wheels or the crank? Is the bike not as fast as it used to be? If any of these questions ring true, it might be time for some bearing maintenance.

What is a bearing?

Simply put, a bearing is a structure that supports a moving part. For instance, when you turn the handlebars to steer your bike, a bearing in the head tube allows the movement between the frame and the fork. Bearings allow your pedals to crank, your wheels to turn, and your back wheel to free-wheel when you are not pedaling.

Bearings consist of several parts: an outer ring, and inner ring, the rolling element whether those be balls or cylinders, and then some sort of retention or cage. As you use your bearings, they wear out, and the spaces between the rings change, leading to clunking or grinding.

Fixing Wheel Bearings

Bicycles have wheel bearings in both the front a rear wheels. To access the wheel bearings, set the wheel on its side. If it is a rear wheel, you will need to remove the freewheel or cassette. From there it is simply a matter of carefully removing the cone with a cone wrench, pulling the axle through from the opposite side, and gently taking out the seals.

It is easiest to use a magnet to remove the ball bearings from the housing. After wiping the grease out of the housing, inspect the inner surfaces of both the inner and outer rings. If they are pitted or scuffed, you need to replace the entire bearing, including the bearing cups. Otherwise, simply apply enough grease to new bearing balls to stick them to the cups, and reverse the process.

Bottom Bracket Maintenance

Modern bike utilize cartridge bottom brackets with bearings that are not meant to be serviced. The bearings are sealed in a housing, and when they wear out, you replace the entire bearing as a unit. 

This is accomplished by simply loosening drive side of the crank, after the crank arms are removed. If you do not have allen-style bolts, it may be necessary to get a crank puller to pull the crank arms. Most bicycles use a left-handed thread on the drive side, so loosen it by turning clockwise. When the drive side is free, you can easily remove the non-drive side with a wrench, in the normal manner. 

Clean and inspect the bearings the same way you would service the wheel bearings, and reverse the removal procedure to re-assemble.

By going through the bearings on your bike at least yearly, you will avoid damage to your frame, and keep your bike cruising like new. If you do not have the tools or know-how to perform bearing maintenance, your local bike repair shop is adept at this task.