What is a headset adjustment?
Your bike may need attention and you may not know it. What is your headset and how do you check in on it? If it was a snake it would have bitten you already. The headset sits right in front of you while you are seated on your bike. It takes its name from the bike frames head tube, hence headset. It holds and carefully balances your handlebars to your fork and ultimately your front wheel. It holds the steering together tightly whilst keeping the steering buttery smooth in rotation.
The headset is comprised of ball bearings, smooth polished hardened surfaces and grease. Although very robust this must be adjusted with care and extreme delicacy. You can find the area to adjust at your stems top cap of a threadless headset. On a quill style stem the headset is adjustable at the very top of the bikes head tube. It is independent from the stem. The term threaded and Threadless refer to the forks steerer tube having or lacking threads.
Determining Play
The best way in my opinion to check for a loose headset if undetectable in normal use is to use the front brake. If it is obvious that the headset is loose you should be able to hear a clunking noise or light ticking if it is very loose. You may also be able to see movement in the headset which would be at the base of the stem. If there is a large amount of play in the headset you may be able to feel the play or looseness while gripping the stem with one hand while standing beside the bike. Do this while gently lifting up as to lift the bikes front wheel off the ground but don’t. Do this only enough to unweight the bike right before the front tire leaves the ground.
Best Method
My favorite way to test for a loose headset is to apply the front brake while straddling or standing over the bike. This way you can balance the bike and test at the same time. I then like to use my thumb and index finger placed both over a stationary portion of the frame (this can be a pressed in headset cup) and the headset. By placing your fingers over a fixed part of the bike frame and the component like the headset you will be able to feel for movement between the two. The last step is to gently motion the bike front to back repeatedly using your fingers that are placed on the headset area. Careful not to confuse the turning of the handlebars left to right with forward and backwards movement.
You should be able to determine if there is movement or not in less than five seconds. Keep in mind not to be rough in this motion, watch that the front tire does not slip forward or backwards during this process on the ground. Imagine that a cup of water has been placed on top of your saddle and try not to spill any water or drop the cup. I usually use the tips of my fingers to apply this motion at the handlebar, stem or headset.
Threadless Headset
A threadless style headset means the forks steerer tube is not threaded. And the stem will need to clamp onto the steerer tube gripping it firmly using only friction.The bolt used to lightly tighten the headset will remove play or looseness from the headset. This bolt (top cap bolt) is attached to the fork via the steerer tube. Using the stem as a spacer or foundation for creating leverage between the top cap and stem to pull up on the whole fork. Removing any play or space. By doing this the bearings are used as a bumper or contact area creating a smooth rolling feel for the steering system.
It is very important to not over tighten this headset bolt also called top cap and preload adjusting bolt. This bolt is typically tightened with care and delicacy. You may use a tool to tighten the top cap bolt but just be aware you are applying pressure to the ball bearings. The ball bearings need some pressure to activate but not too much pressure. As they will not move with ease if they are overtightened. The ball bearings will be smothered and steering will feel tight and restricted during rotation.
Over tightening a headset can and will prematurely wear out the bearings and the surface that they roll on, we call this area the race. The race and the ball bearings will get out of round and scoring will occur. Once this happens smoothness and adjustability will be compromised and the headset can be replaced at this time. I have seen headsets that have been overtightened for a long time and a simple adjustment of loosening the top bolt usually can fix this problem without residual damage. Anything past this will damage the headset bearings.
Making the Adjustment on Non Threaded
None of this can be done successfully on a threadless headset until the stem bolts have been loosened. The bolts do not need to be moved, just loose enough to loose the grip if the fork (front wheel). Do not worry about the front wheel alignment at this time, you may realign your handlebars as the last step. If the headset is extremely loose tighten the top cap bolt with a tool and light finger tips to the point of some resistance. Once the residual play is gone start you're fine adjustments here.
Turn the top cap bolt a half turn at a time testing for play after every adjustment, patience is key here. You want the play to just disappear, once the play has been successfully removed from the headset tighten the bolt an additional quarter turn. After a couple rides recheck your headset for play. It is not uncommon for settling to occur especially on a fresh installation. Realign the handlebars and front wheel at this time and tighten the stem bolts to the recommended torque by the stem’s manufacture.
Threaded Adjustment
An adjustment for a threaded headset may require the use of two wrenches, specifically headset wrenches. Headset wenches are very thin. You may be able to use one wrench and an adjustable wrench. There may be two similar looking adjustment bolts, the bottom one is the one making contact with the bearings so take care in this incremental adjustment. Once the play has been removed hold this bolt firmly in place as to be fixed and then tighten the top bolt with the appropriate tool. You are in essence locking the adjustment into place. This pressure should be very tight.
For a final check of the headset lift the front wheel off the ground by about two inches by the handlebars and rotate left to right. You are feeling for smoothness or roughness in the form of resistance. If this occurs loosen the headset by a quarter to a half turn at a time. I you are unable to remove the play and maintain a free flowing movement of the handlebars then it is possible the headset has permanent cage or the initial installation was compromised. A disassembly and inspection is due. How fun is this!