Bottom Bracket

The bottom bracket is the axle and bearings on which the crankset rotates. This section explains how to inspect, adjust, and lubricate your bottom bracket.

FIGURE 1: Parts of the bicycle drivetrain

INSPECTION

Every 3 months check the bottom bracket adjustment.

To check the bearing adjustment

1. Lift the chain from the chainrings.
2. Rotate the crank so that one of the arms is parallel to the seat tube.
3. Put one hand on the crank arm and one hand on the seat tube, and attempt to move the crank arm laterally toward and away from the seat tube.
4. Spin the cranks.

If the crank feels or sounds loose, or if the motion stops abruptly or you hear a grinding noise coming from the bearings, the bearings need to be adjusted or re-greased by your Trek dealer.

ADJUSTMENT

Adjustment of the bearings in the bottom bracket requires special tools and training. These services should only be performed by your Trek dealer.

If needed, tighten the bottom bracket cups to the correct torque.

LUBRICATION

Once a year, re-grease the bottom bracket bearings. Some bottom bracket bearings are permanently sealed and do not require yearly re-greasing. Re-greasing bearings requires special tools and training, so this should only be done by your Trek dealer.