Your headset is a system made up essentially of two sets of ball bearings. These ball bearing sets are located just above and just below your frame's head tube. The headset allows your handlebars, stem and front fork to turn freely inside of the head tube.
Dismantling of a headset is not for the faint hearted and is subsequently not covered here. Removing and replacing headsets requires specialist tools, tools that are very expensive, often well beyond the finances of the cyclist. Therefore, other than routine inspection and maintenance, you are best to take a problem headset to the specialist.
To many cyclists it is the last thing that they think to check, yet it is probably one of the most important components on any bike. Look after the headeset and you won't even notice the attention you give it, you'll just enjoy smooth turning and effective stopping.
Common Headset Problems and Solutions
Poor headset adjustment
Solution - These can be complex procedures, and are often best left to the skilled cycle mechanic. If however you wish to make the adjustment yourself first make sure you have the correct sized headset spanners, yes you need two. Don't use adjustable wrenches as these can slip and cause damage.
There are basically two nuts to "adjust", one is actually a locking nut. First loosen the top nut. This may already be loose, clearly indicating there is a problem. Tighten, or loosen, the nut below the locking nut until you get the movement you wish from the headset. Then, whilst holding this nut in place with one spanner, tighten the top "locking nut" with a second spanner.
Bearing system damage
Solution - Bearing system problems are also often beyond the abilities of most "home mechanics". If you think the bearing system is damaged you should really take you bike to your nearest CoBR member.
You should check your headset to make sure it's secure and that it allows for smooth steering. You should perform the following headset checks before every ride.
To check for good headset adjustment, apply the front brake fully and push backwards and forwards against the grip of the brake. There should be no looseness, play, or knocking in the headset. If there is, turn the handlebars 90 degrees and try again, this will ensure the looseness is in the headset and not your brakes.
Special note: If you have front shock absorbers, compress them slightly before performing the test.
The bearing systems are designed to provide a full range of smooth, jerk-free rotation. To check, lift your front wheel off the ground and turn the handlebars slowly backwards and forwards. Well-tuned bearing sets will give you a smooth rotation. If damaged or poorly adjusted they will either bind during the rotation, or feel rough or jerky. As you perform these checks, ensure your brake and gear cables aren't interfering with rotation of the handlebar.
Also, listen for grinding sounds, rattles, or other noises from your headset. These can all be signs of bearing system problems.