Trek BB90 Bearing Kit Installation

This guide explains how the Hambini Trek BB90 Bearing Kit works and how to install it.

How this kit works

Trek BB90 consists of a bottom bracket containing a 90mm wide shell with apertures for a 37mm 6805 type bearing. Originally Trek used MR2437 bearings which have a 24mm bore, 37mm width and 7mm thickness. Subsequently, they moved to a standard 6805 bearing which has a 25mm bore, 37mm width and 7mm thickness.

Trek bottom brackets are typically at the loose end of the tolerance spectrum and often exceed this. Bearings are also made to a tolerance. The Hambini kit selects bearings that are the top end of the tolerance band to try to ensure a sufficiently good fit to stop creaking.

For example, an Enduro bearing with 36.97mm outside diameter may give creaking and rotate within the housing whilst a slightly larger NSK/FAG/NTN bearing at 36.99mm will not.

There are inevitably some limitations, if the bike has been ridden with a spinning bearing for an extended period, the bottom bracket may have fretted to the point that no bearing will work. In this scenario, a Hambini Kit would not overcome this problem. The bottom bracket would require relining.

Equipment required

  • Hambini BB90 Kit
  • Cleaning Cloths
  • Cleaning Spray
  • 6805 Press
  • Loctite 7649 Activator or equivalent
  • Loctite 641 Medium Strength Retaining compound or equivalent

Installation Procedure

  1. By default, the delrin top hats are installed in the bearings for transit purposes, this is to prevent them from being damaged. These need to be removed from the bearings prior to installation.
  2. Ensure the Trek Frame is completely clean of any grease, contaminants and dust. A fast acting industrial cleaner is recommended for this purpose.
  3. Spray on Loctite 7649 Activator, wipe off any excess from around the frame and leave it to dry for 24 hours.
  4. The outer race of the bearings needs to be cleaned with a cloth, do not use degreaser.
  5. Spray the frame with Loctite 7649 activator and leave it until it evaporates (usually 5-15 minutes)
  6. Apply a liberal coating of Loctite 641 retaining compound to the bottom bracket shell
  7. Press the bearings into the bottom bracket shell. The bearings are 6805, a 6805 press will be required.
  8. Wipe off any excess retaining compound. Do not use degreaser
  9. Leave the frame for 48 hours.
  10. Press the delrin top hats into the bearings
  11. Reinstall the crankset