Replacing Fork Bearings

When riding a motorcycle, we have to rely on one type of bearing or another. There are a few different styles of bearings employed in the smooth operation of any motorcycle. For instance, there are engine bearings - roller, ball and needle - that keep the internal components spinning in harmony. Wheel bearings allow the bike to roll down the road, and bearings on the front end allow the bike to turn.

The setup and maintenance of any bearing can extend or shorten its life, but especially so when it comes to the steering stem bearings of your motorcycle's front forks.

For the sake of this publication, we will limit our focus to the tapered roller bearing most commonly used since the introduction of the hydraulic front forks in 1949.

The front fork stem requires two bearings, one on the lower triple tree and one under the top triple tree. The fork stem bearing races are pressed into the frame, and the bearings fit on the fork stem, allowing the front end to be turned from side to side smoothly.

The fork stem bearings operate under a small amount of preload, which is determined on each individual motorcycle by what is known as a fall away test.

The proper setup of the fork stem bearings is essential to the handling characteristics of your motorcycle. Too loose, and the bike will display an unnerving shimmy while riding. Too tight, and the bike will wander on the freeway, and make low-speed handling seem like a chore.

The replacement of fork stem bearings should be complete - meaning you should replace both top and bottom bearings and races at the same time. A good rule of thumb to follow, when it comes to fork stem bearings, when it comes to fork stem bearings, is when in doubt, replace.