How to Fix a Loose and Rotating Bicycle Handlebar

Two words you never want associated with your bicycle handlebar are “loose” and “rotating.” Your handlebar needs to be firmly clenched in place, or you may find yourself loose and rotating in a fall on the pavement -- not the best place to be. Beautifully designed, strong handlebar clamp bolts tend to stay nice and tight without problems for ride after ride, even over rugged terrain, but if you have a crash or mishap, you may need to break out your Allen key set to fix a problem with your handlebars.

Examine your bicycle stem design, looking for whether the clamp has a single pinch-style bolt -- indicating a quill design -- or a pair of bolts holding a removable faceplate, indicating a threadless design. BMX bikes may have a faceplate with four bolts in fact.

Straddle your front wheel and center the handlebars horizontally, eyeballing them to see if they seem correctly positioned equally on either side of the stem. Gently tighten the single pinch bolt, typically with a 6 mm Allen wrench, or double faceplate bolts, typically with a 5 mm Allen wrench, depending on your stem style. Avoid overtightening; you want to allow additional rotational adjustments while roughly maintaining the bars’ horizontal position.

Rotate the handlebars just enough so that the bottom of the drops are horizontal to the ground. Finish tightening the bolts -- just rotate the Allen key firmly on a pinch-style bolt. Tighten paired faceplate bolts evenly, so that the little gap between the faceplate and the end of the stem remains even. Tighten BMX bolts, typically with a 6 mm Allen wrench, by crisscrossing two diagonal bolts and then the other two to keep the torque even.

Tips

If you discover that the completely tightened bolts do not lead to a rock-solid firm hold on quill-design handlebars, insert a shim cut from a soda can with tin snips between the clamp and the handlebars, advises professional bike mechanic Daimeon Shanks in “Essential Bicycle Maintenance and Repair.”

If the gap seems too great for this homespun repair, or you have a threadless stem, you may have a mismatch between a too-thin handlebar diameter, say 7/8 or 1 inch, and a stem opening of up to 1 1/8 inches. You can obtain commercially made handlebar shims that come in pairs -- simply slip these on the top and bottom of the center of the handlebar where it meets the stem and tighten the bolt around the bar and shims.