Having a stem that isn’t perfectly straight, a headset that clunks, or handlebars that are simply not at the right height are problems that are very easy to fix – it’s a simple bit of bike maintenance. Here is how to do it.
1. Undo headset bolts
Undo the two bolts at the side of your stem so that they are just loose — don’t undo them entirely. Then undo the headset top bolt. You might need a different size of Allen key than you did for the stem bolts.
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2. Move headset spacers
If you want to alter bar height this can be done with the spacers beneath the stem. If you lower the stem be sure to put the spacers above the stem. The amount you can add beneath depends on how far down the fork column has been cut. Be sure to line up the stem so that it’s straight. Stand directly behind your saddle (straddling your rear wheel) and run your eye along the top tube, stem and front wheel so that they are all in line.
3. Tighten the top cap
When tightening the headset top cap it MUST push down on the stem, or the spacer above it, and not the fork column itself (the top cap pushes down on the headset which tightens it up). Do up the headset top cap until it is just tight — at this point you should be unable to turn your stem spacers. Do not overtighten it. A torque wrench is a good idea at this point.
4. Do up the side bolts
Alternate between each side as you do them up. Ideally, use a torque wrench if you have one so as not to over-tighten the stem on to the fork column.
5. First test
Lift the front of the bike off the ground and let the front wheel and handlebars flop from side to side. If it’s smooth, that’s good; if it’s stiff, the headset bolt was done up too tight, so try again.
6. Second test
Hold the join between the stem spacers and the bike frame. Put on the front brake and rock the bike back and forth. If there is any movement between the bike and the spacers the headset bolt isn’t tight enough, so try again… and again!