document updated 15 years ago, on Sep 2, 2009

My friend and I both have threadless headsets (the stem clamps around the steer tube), so these are all about threadless:

If all you have to do is adjust the headset's tightness, and not replace anything, then it's pretty simple:

There are two types of bolts you'll be using here:
- the "cap bolt" or "preload bolt", seen here
- the two "stem bolts", seen here
Loosen the stem bolts somewhat, enough that the stem isn't solidly attached to the tube
Tighten or loosen the preload bolt until it's adjusted properly
- Stand astride the bike, lock the front brakes, and rock the bike foward and back. If the headset is too loose, it'll "clunk" and the two parts of the headset will relative to each other an obscene amount.
- If it's WAY too tight, when you turn the handlebars left or right, it won't turn smoothly.
- However, you don't want to get it very tight either. Tighten it JUST a little beyond the point that it's no longer loose.
After the preload bolt is adjusted properly, tighten the two stem bolts VERY TIGHTLY. If these aren't tightened properly, and they come loose while you're riding it, YOU WON'T BE ABLE TO STEER AND YOU'LL UNAVOIDABLY CRASH. BE SURE it's tightened properly!!