Stairmaster 4400 & 4600 Eccentric Hub Installation,Adjustment

This video covers the installation and adjustment of the Eccentric Hub Assembly for the Stairmaster 4400PT/CL and 4600PT/CL Steppers.

The video begins with the Eccentric Hub Assembly removed from the unit. If you need help removing the Eccentric Hub Assembly from your stepper, please see our video about the Eccentric Hub Assembly Removal.

Tools Needed:

  • Socket Wrench
  • 7/16” Socket
  • Adjustable Wrench or 7/16” Wrench


  1. Begin by placing your HTD toothed belt around its pulleys.
    1. This allows you to set the proper belt tension before mounting the Eccentric Hub Assembly to the frame.
    2. The “egg” shape of the Eccentric Hub allows for adjustment of the belt tension.
      1. Rotate the hub counterclockwise to tension the belt.
        1. Proper belt tension allows about ¼” of deflection.
  2. Line up the 4 bolts through the Eccentric Hub Assembly and the frame.
    1. Be sure to place the bolts facing the same direction as noted from the removal of the old Eccentric Hub Assembly.
  3. Once all the bolts are aligned, retighten them to the frame using the socket wrench with socket on one side and the other wrench on the opposite side.
  4. Reinstall the poly-v alternator belt.
  5. The eccentric hub assembly installation and adjustment on your Stairmaster 4400 or 4600 stepper is now complete.
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