Workshop: How to service a headset
By George Ramelkamp, Cycling Plus | Wednesday, July 1, 2009 9.40am
A headset that is either too loose or overtightened can ruin your ride, so it's important to sort it out as soon as possible. Different kinds of headsets require various techniques for adjustment and we’ll go through a selection here.
Some of the following advice 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.
- 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
- FSA headset guide tool (measures cartridge angles and diameters, available at www.fullspeedahead.com)
- Thin threadless headset washers (www.hopegb.com)
- 5/32 or 1/8in loose ball bearings or headset cartridge bearings
1 Diagnose and adjust a threaded headset
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, it’s either overtight 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.
2 Quill stem removal
For older 1in 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.
3 Inspection: Cone and cup wear
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.
4 Dealing with the wear
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 step 5 below if you have an Aheadset.
5 Aheadset/threadless headsets
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.
6 Get a grip
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).
7 Remove cartridges
If a simple adjustment doesn’t do it, 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.
8 Replace cartidges
Now compare the two cartridges and notice the differences in the length of the angled and straight sections. These cartridges are available in a number of configurations, so hang onto 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; to make it less of a chore, FSA produce a smart template (see ‘Tools’), consisting of a metal plate featuring different cup and cartridge profiles.
Replacing the cartridges 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 produce 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.
10 Mind the gap
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. 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 as in step 5: the twin bolts should be about 5.7Nm.
You can follow BikeRadar on Twitter at twitter.com/bikeradar and on
Facebook at facebook.com/BikeRadar.
can also improve your fitness and train with us on training.bikeradar.com.