A headset that’s set up correctly delivers effortless steering and extends the lifespan of your bike’s parts. Below is the step-by-step process for tuning the modern threadless style headset.
Threaded vs. Threadless Headsets
Tools you’ll need include hex wrenches and a torque limiter.
Before you begin, figure out which type of headset your bike has. A threadless system pairs with a fork whose steering column is smooth, with no threads. The stem and spacers slide onto this column, and a top cap sits at the very top. That top cap is what determines the bearing preload, and once you’ve dialed it in, tightening the stem onto the column locks everything in place.
A threaded headset, by contrast, uses a fork with threads on the steering column. An adjusting race and a locknut screw onto the column, which sets the bearing tension and holds the fork inside the frame. A quill stem then drops into the column.
These explanations are simplified, but visually telling the two apart is simple. If you can see wrench flats sitting above the top cup, you’re looking at a threaded headset.
Diagnosing the Problem
Every bearing on a bicycle creates some friction as it spins. That’s completely normal and won’t affect your ride. Higher-quality bearing surfaces are ground more smoothly, so they produce less friction and resist turning less. Adjustable bearing systems rely on two opposing races that can be shifted relative to each other.
When a headset is too loose, the bearing system develops play. The bearings shift up and down and get rattled or slammed against the race surface with every tiny impact the front tire takes. Over time, this wears down the race surfaces and can even distort the ball bearings. A loose headset can also make the bike handle poorly.
To test for looseness, squeeze the front brake and place your free hand over the headset and head tube. Rock the bike back and forth and feel for movement between the parts. A knocking or rocking motion between the frame and the threaded race signals a loose headset.
A headset can also be adjusted too tightly. Running it too tight speeds up wear and can cause the bearings to become “indexed” or feel “notchy.” A headset that’s overly tight often feels stiff and rough.
The ideal adjustment is as loose as possible while still eliminating all play.
Making the Adjustment
Threadless headsets operate on the same principle as threaded ones. The bearing races must press against the bearings. The bolt in the top cap applies pressure to the stem, which pushes down on washers beneath it, which press on the bearing races, which in turn press against the bearings.
NOTE: The cap and bolt at the top of the stem do not hold the stem onto the steering column. It’s the bolt or bolts on the side of the stem that keep it from moving once you’ve made your adjustment. The cap exists solely for bearing adjustment.
Start by removing the adjusting bolt at the center of the steering column, then take off the top cap. Inside the column you may find a star-shaped nut or similar fitting. The bolt threads into this fitting and pulls the fork against the headset bearing surfaces, tightening the adjustment. Check the height of the steering column relative to the stem. It should sit roughly 3mm (1/8″) below the top of the stem. The stem needs to press down on the spacers for the bearings to adjust properly. If the column is level with the top of the stem, you’ll need another spacer beneath the stem.
Remove the bolt and top cap to inspect the steering column. Lubricate the adjusting bolt, then reinstall the cap and bolt by hand only. Don’t tighten them.
Loosen the stem bolt(s) holding the stem to the steering column. Lubricate these bolts if they’re dry. NOTE: Never lubricate the inside of the stem or the surface of the steering column.
Wiggle the stem side to side to confirm it’s loose. If the stem is stuck or rusted to the column, no adjustment is possible.
Align the stem straight with the wheel and gently tighten the top bolt. Stop as soon as you feel any resistance.
Tighten the stem bolt(s).
Check for play by pulling the fork back and forth. Turn the handlebars in various directions while checking. Some play may remain at this stage. Be careful when grabbing suspension forks, since the legs themselves may have play. Grab the upper portion of the fork instead.
To fine-tune the bearings, loosen the stem bolt(s).
Turn the adjusting bolt in the center cap just 1/8th of a turn clockwise.
Tighten the stem bolts and check for play again.
Repeat these adjustments until the play is gone. Always remember to loosen the stem bolts before turning the adjusting bolt in the cap.
Check the stem’s alignment and fully tighten the stem binder bolts.
NOTE: Another way to test for play is to set the bike on the ground and grip the front brake firmly. Push down on the handlebars and rock the bike forward and backward. A knocking feeling can indicate a loose headset. This essentially does the same thing as pulling on the fork. However, play in the brake caliper arms can also produce a knocking sound. Front suspension forks may have play in their legs too, which also causes knocking. If the adjustment feels extremely tight, other headset issues may be at play. Bearing surfaces could be worn, the ball bearing retainers might be upside down, or a seal could be misaligned. If play persists no matter how you adjust, the steering column may be too long for the stem and top cap. In that case, add spacers beneath the stem.
Troubleshooting
If you can’t seem to find the sweet spot between too tight and too loose, several factors could be responsible:
Bearing Quality
Bearing surfaces are made of hardened steel and are typically cut by grinding. Round ball bearings roll along the curved surface of the cup and cone. Even the finest bearing surfaces carry faint grinding marks. Smoothness varies between manufacturers and models. Some bearing systems simply feel smoother because they genuinely are smoother. That’s why judging adjustment by feel alone is unreliable. As a rule, adjust bearings to the loosest setting that produces no knocking or play, regardless of how smooth they feel.
Worn-Out Headset Components
If a headset still feels rough and excessively sticky even after being adjusted for tightness, it may simply be worn out and need replacing. Keep in mind that lower-end components will generally feel less smooth even when properly adjusted, while higher-quality headsets and bearings feel smoother.
If the headset seems to lock in place or center itself when the wheel is straight, the lower races likely have dents from the ball bearings. The result is the headset locking into one forward position. Replacement is necessary.
See Threadless Headset Service for more details on replacing threadless headset components.
Headset Cannot Move Freely with No Play
This can occur if a component is out of position or the bearing cage was installed upside down. Take the headset apart and confirm everything is correctly placed. See Threadless Headset Service for a detailed walkthrough of proper component orientation.
Loose Cups or Adapters
Over time, a loose headset can allow play in the cup or adapter, wallowing out the head tube. Bearing adjustment won’t fix this. If a cup or adapter is loose enough to turn by hand while installed in the frame, you may be able to secure it with retaining compound. Otherwise, it might be time to consider a new bike. Consult a professional to see if another solution exists.
