Adjust Threadless Headset
For detailed photos of individual headset components, see Headset Parts.
The only tools needed to adjust a threadless headset are hex wrenches, usually 5 or 6 mm. A secure work stand is very useful.
The procedure to adjust a threadless headset is:
1. Preferably, put the bike in a work stand.
2. Loosen the bolts (counterclockwise) holding the stem to the fork. A threadless headset cannot be adjusted with the stem tightly attached to the fork steering tube.
3. Tighten or loosen the stem bolt that is inserted in the top of the top cap, usually with a 5 mm hex wrench. This adjusts the pressure of the races on the ball bearings. Clockwise tightens, counterclockwise loosens. Find the precise adjustment that allows the fork to rotate freely without catching, but which securely holds fork steering tube in the bike's head tube with absolutely no play.
4. Tighten the bolts holding the stem to the fork. Careful--these strip easily, so don't over-tighten. Tighten until you cannot move the stem laterally.
5. Test the headset adjustment.