Spring Pulley,Chain,Drive Hub Replacement Video for Stairmaster Stepper, SC916

Video about the Drive Hub Replacement Procedure for Stairmaster Steppers

This video covers replacing the spring pulley, the step chain, and the drive hub assembly on the Stairmaster steppers. The same steps apply to all stepper models from the beginning 4000PT to the model SC916 as used in the video.


  • Snap Ring Pliers
  • Tip Kit for Snap Ring Pliers
  • Socket Wrench
  • 7/16" Socket
  • 7/16" Wrench
  • Needle Nose or Standard Pliers
  • Safety Goggles


  1. Begin by disconnecting the spring.
  2. Do this by pulling up on the spring and unhooking the spring from the frame post.
  3. Next, using the snap ring pliers and proper tips, remove the snap ring from the spring pulley shaft. **Important: Be sure to wear safety goggles when working with snap rings**
  4. Remove and inspect the spring pulley for any flat spots replacing the pulley if necessary.
    1. Flat spots develop over time and can result in roughness in the pedals.
  5. On the side that the pulley was just removed, slowly press the pedal down.
  6. Remove the step chain retainer brackets (if equipped) using the 7/16" wrench, 7/16" socket, and socket wrench.
  7. Once the retainer bracket is removed, the spring can be lifted up over the drive sprocket and disconnected from the chain.
    1. The spring is opened at one end to allow for maneuvering over the link.
  8. Using the standard or needle-nose pliers, remove the master link attaching the step chain to the pedal arm.
    • Place one jaw of the pliers against the open end of the clip (if installed correctly, the open end of the clip is opposite the direction of chain travel) and the other jaw of the pliers against the far side of the nearest rivet coming through the keeper link, and squeeze pliers together.
    • This should pop the clip free allowing you to remove it from the master link.
    • Next, remove the link bar.
    • Finally, remove the master link disconnecting the chain from the pedal arm.
  9. Inspect the new step chain making sure all the chain links flex.
    • The manufacturer recommends lubricating the step chain with 30W motor oil using a clean rag to remove any excess.
  10. Attach the new step chain to the pedal arm reversing the steps taken to disconnect the chain.
  11. Relieve tension on the opposite spring by lifting up on the spring and unhooking it from the frame post.
  12. Slowly press the pedal down.
  13. Feed the spring around the pulley and lift the chain up over the sprocket to move it out of the way.
  14. Disconnect the remaining two bolts from the drive hub assembly.
  15. Lift the drive chain over the sprocket and pull the drive hub from the frame.
    • As the drive hub assembly starts to develop problems, you may feel clicking, hear some grinding sounds or a pedal may stick in one position (which usually happens on one side); All of which are indicators of a worn drive hub assembly.
    • The drive hub can be replaced as a complete unit.
      • The drive hub consists of (3) sprockets.
        • Two one-way clutch sprockets - these sprockets drive in one direction and slip in the opposite direction which are for the step chains.
        • A larger sprocket that spins either direction and is for the drive chain.
    • An inspection of the drive hub can help determine the need for replacement.
          • If either of the one-way clutch sprockets slip in both directions, they need to be replaced.
          • If there is a catch in any of the sprockets in any position, then it likely needs replaced.
  16. Reinstall the drive hub the same way it was removed.
  17. Slip the drive chain over the drive sprocket before mounting the hub assembly to the frame.
  18. Once the drive hub is bolted to the frame, reinstall the step chains on each side.
  19. Place the free end of the step chain (opposite the pedal arm connection) up over the step chain sprocket.
  20. Lift up on the pedal and pull down on the step chain.
  21. Place a hand on the sprocket keeping the step chain from feeding back and allowing the pedal to drop.
  22. Grab the spring with your opposite hand and join the spring to the step chain.
  23. Once the spring is attached to the chain, press the pedal down again.
  24. Reinstall the spring pulley and the snap ring onto the pulley shaft.
  25. Lift up on the pedal and pull the spring to route through the pulley, hooking the spring onto its frame post.
  26. Repeat these steps to attach the step chain and spring on the opposite side.
  27. Reinstall the step chain brackets (if equipped) making sure all bolts face the same direction.
  28. This concludes the video demonstration of replacing the drive hub, spring pulley, and chains on the Stairmaster steppers.
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