How to Use Seatpost Shims

A seatpost is a tubular support that allows a bicycle saddle to attach to a bicycle. The seatpost can be raised or lowered, allowing the cyclist to set the saddle to a suitable height. Bicycle frame seat tubes come in different sizes, and the diameter of a seat tube may be too large for the diameter of a particular seatpost. Specially designed shims allow such a seatpost to be safely used with a larger diameter seat tube.

Things You'll Need

  • 4 mm hex wrench (as needed)
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Instructions

    • 1

      Install the narrow end of the seatpost shim into the bicycle frame down tube. There is a "collar" at the top of the shim that will prevent it from disappearing entirely into the down tube.

    • 2

      Rotate the shim so that the opening along the length of the shim is facing the rear of the bicycle.

    • 3

      Fit the seatpost collar atop the seat tube. The collar may already be in place. The collar is a narrow clamp that tightens the seatpost to the seat tube.

    • 4

      Loosen the seatpost collar. The collar will have either a quick-release or single bolt. Open the quick-release lever. Otherwise, use a 4 mm Allen wrench to loosen the bolt.

    • 5

      Push the seat post down into the seat tube until the saddle is at the preferred height.

    • 6

      Position the tip of the saddle so that it is pointing forward. Tighten the seatpost collar, either by closing the quick-release or tightening the bolt.