How to Fix a Loose Stem on a Bicycle Handlebar

A handlebar stem is crucial to the operation of a bicycle. The stem serves as bridge between the handlebar and the fork. When handlebars are turned in any direction, the stem ensures that the fork and wheel turn in perfect union. There are two common types of stems--threaded and threadless. Threaded stems are "threaded" into the bicycle frame head tube. Threadless stems slide over the fork tube. Fixing a loose stem ensures tighter and more accurate steering.

Things You'll Need

  • 6mm hex key (as needed)
  • 5mm hex key (as needed)
  • 4mm hex key (as needed)
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Instructions

  1. Threaded Stem Tightening

    • 1

      Use a 6mm hex wrench to loosen the bolt at the center of the stem. The bolt may already be loose, but loosening it further allows for adjustment of the stem prior to tightening.

    • 2

      Position the stem until it is aligned with the top of the front wheel.

    • 3

      Hold the wheel in place with both feet, and use the 6mm hex wrench to tighten the bolt at the center of the stem.

    • 4

      Move the handlebar back and forth to be sure the bolt is not too tight. If the bolt is too tight, the steering will bind when turned. Loosen the bolt slightly if this is the case, and check the adjustment once again.

    Threadless Stem Tightening

    • 5

      Loosen the bolts at the side of the threadless handlebar stem with a 4mm hex wrench. Depending on the individual stem, there will be either one or two bolts. Loosening any bolts before tightening them allows for adjustment of the stem.

    • 6

      Loosen the bolt at the center of the stem with a 5mm hex wrench.

    • 7

      Turn the stem so that it and the top of the front wheel are aligned. Straddle the wheel to keep it from moving, and tighten the bolt at the center of the stem.

    • 8

      Tighten each bolt at the side of the stem.

    • 9

      Turn the handlebar back and forth to check the adjustment. If the steering binds when turned, loosen both side bolts and the center bolt one-quarter turn. Retighten the side bolts, and check the adjustment once again.