How to service a headset and replace headset bearings

Eliminate play for smoother, more effective steering

If you're experiencing play (unwanted movement) in your headset, or a rough grinding when you turn the bars, it's likely that it's time to service your headset or replace the headset bearings.

Most modern bikes use two sealed bearings positioned at the top and bottom of the head tube. We've put together this simple video guide to show you how to service the headset on such a bike. Different bikes come with different headsets, so a selection of common types are displayed below. Written instructions for this task are also outlined.

Some of the advice that follows should be seen as a temporary measure, useful in order to stretch out the life of your headset until you can find time to get it replaced. If the following steps don’t get results, or you’re still concerned about safety after the adjustments, then get the job done professionally by your local bike shop.

How to service a headset and replace headset bearings

Tools required

For most modern headsets you shouldn't need any special tools
For most modern headsets you shouldn't need any special tools

  • Headset wrenches (32 or 36mm)
  • 4, 5 and 6mm Allen keys
  • Resin hammer or block of wood and hammer
  • Grease and citrus degreaser
  • Torque wrench
  • Thin threadless headset washers (www.hopegb.com)
  • 5/32 or 1/8in loose ball bearings or headset cartridge bearings

How to diagnose and adjust a threaded headset

Older, threaded headsets will require a couple of spanners to adjust
Older, threaded headsets will require a couple of spanners to adjust

Bounce the front wheel off the ground a few times: a rattling sound indicates the headset is loose. If the bars lock in the middle and point straight then it’s either too tight or the bearings are heavily worn. Holding the front wheel or frame between your legs, with the bars as leverage, carefully place a 32mm headset wrench over the locknut and turn anticlockwise.

If it’s particularly tough, try turning the lower cup clockwise to free it, releasing the top locknut. Adjust the lower cup until there’s no play, but free movement, then lock down the top nut.

How to remove a quill stem

Removing a quill stem will often require a tap with a mallet
Removing a quill stem will often require a tap with a mallet

For older 1-inch quill stems, you’ll need to dislodge the stem wedge first in order to remove the stem. Using an Allen key, loosen the wedge bolt by turning it anticlockwise until it protrudes just enough to give it a sharp blow with a resin mallet (keep a few threads engaged to prevent the cone or wedge from dropping into the steerer).

Remove the stem and bars, and attach them to the bike’s top tube with an old toe strap. Drop the fork by removing the brake, and the mudguard if required, then unthread the locknut and upper cup. Remove the bearings and clean with degreaser/WD40 and a cloth.

How to inspect for cup-and-cone wear

In this case, cone and cup wear is pretty easy to see
In this case, cone and cup wear is pretty easy to see

The following applies to all standard ball bearing headsets. Look closely at the surfaces of the bearing path — if it’s worn, then evenly spaced pockmarks should be clearly visible, each little crater corresponding to an individual ball bearing. When the headset is ridden too tight or too loose over extended periods, each bearing gradually carves out a little nest for itself. The process is greatly accelerated by grit and contamination from wet conditions. There is a fix, however: packing in extra bearings where there were none before.

How to deal with cup-and-cone wear

Replacement ball bearings should be available at your local bike shop
Replacement ball bearings should be available at your local bike shop

Having removed the fork and ensured everything is clean, take a few of your bearings to your local bike shop for a match — they’re relatively cheap and will either be 1/8 or 5/32in in diameter. Now add a dollop of grease, enough to hold the loose balls in place, and add bearings until they fill the cup, ensuring they’re correctly positioned in the race on the bearing path.

Because we’re cheating a bit here, it’s okay if they touch lightly. The idea is to end up with bearings occupying the undamaged areas of the cones and cups. Then readjust the headset correctly — refer to the step below if you have an Aheadset.

Aheadset/threadless headsets

If your headset has developed play then the first thing to check is that the headset bolt hasn't worked loose
If your headset has developed play then the first thing to check is that the headset bolt hasn't worked loose

In order to readjust the headset correctly, you need to understand that the stem has to be able to slide up and down on the steerer and should be loose before tightening the top cap.

First, release the steerer clamp bolt or bolts on the stem completely. Make sure you alternate for twin bolt stems, since loosening one bolt tightens the other. Now nip up the top cap bolt. This will draw the fork upwards, sandwiching and tightening the bearings, so don’t overdo it. Tighten twin stem bolts gradually until an even torque of 5-10Nm is achieved.

The common star-fangled nut (R) or wedge type nut used frequently with carbon steerers (L)
The common star-fangled nut (R) or wedge type nut used frequently with carbon steerers (L)

Aheadsets or threadless headsets rely on an internal ‘gripper’ device placed in the fork steerer tube, which is pulled up using the bolt held in place by the top cap. This draws the bearing assembly together by pulling against the stem, making adjustment possible. It’s therefore necessary for the top of the stem clamp to sit a few millimetres higher than the top edge of the steerer tube.

The star-fangled wedge on the right of the above image is used to grab steel and aluminium steerers. The wedge on the left is preferable for carbon or thin-walled aluminium steerers. If you have a deeper nylon stem cap (as on the right headset), ditch it for a shallower alloy one (as on the left).

How to remove cartridges

Removing cartridges can be a little fiddly so take your time
Removing cartridges can be a little fiddly so take your time

Replacing cartridges or loose bearings is relatively easy. Remove the top cap and stem, and if the fork doesn’t simply pull out, tap the steerer with the resin hammer to dislodge it. If it proves unruly, try prying the upper cone wedge away from the cone, holding onto your fork to keep it from falling to the floor.

Note that if you have a Campagnolo headset with an expander wedge instead of a star-fangled washer, the non-split cone wedge can sometimes become stuck due to slight expansion of the steerer tube (this goes for some Dia-Compe models too). In this case, loosen the expander wedge first with a few turns of its Allen bolt, then give it a tap.

How to replace cartridges

Notice the differences in these cartridges
Notice the differences in these cartridges

Now compare the two cartridge bearings and notice the differences in the length of the angled and straight sections. These bearings are available in a number of configurations, so hang on to your originals to ensure you can always get a good match. If you have a seriously neglected fully integrated headset or lower cup, a thin strip of PTFE tape and a few drops of bearing adhesive might be your only recourse.

With today’s modern integrated headsets, determining which kind of bearing goes into the frame can be a hit-and-miss process; so it's important to make sure you have the right components. If you're unsure if you have the correct bearing, contact your local bike shop or the manufacturer.

Troubleshooting

Tiny spacers such as this one from Hope can be the difference between rough and smooth steering
Tiny spacers such as this one from Hope can be the difference between rough and smooth steering

Replacing the cartridge bearings should remedy the rattle and poor steering. Sometimes the upper cup, cone wedge, spacers and stem won’t adjust correctly due to the upper edge of the top cup coming into contact with the lower edge of the cone cap. This is a frequent problem that will cause binding of the headset and handling difficulties. The resulting friction can be remedied with a thin spacer or two (Hope produces one that's 0.4mm thick) that will prevent the edges from coming into contact and causing drag when placed between the cone wedge and cone cap. Apply a thin layer of grease between the metal elements and take care to avoid carbon steerers.

Mind the gap, 2-3mm is perfect
Mind the gap, 2-3mm is perfect

Note that when dealing with headset adjustment the stem is already level or slightly below the upper edge of the steerer, with the stem cap bottomed out. This means you’ll need to stack enough spacers below or above the stem to achieve the gap illustrated above (2-3mm is ideal). If you don’t have sufficient stem or spacer protruding, you won’t be able to correctly adjust the headset.

Now ditch the nylon top cap (shown on the right) in favour of a shallow alloy one. Check the expander wedge or star-fangled washer is well anchored and not slipping upwards. Make the final adjustment by acting on the top cap bolt, then carefully re-torque the stem. The twin bolts should be about 5.7Nm.

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