Workshop: Servicing a front hub
By Cycling Plus | Wednesday, June 17, 2009 8.00am
If your front wheel feels rough and nasty when you spin it, a hub service could be in order. Here we’ll talk you through the two main types: standard cup-and-cone (with loose balls) and sealed cartridge-type hubs.
Cost: A set of balls and cones costs £5-£10. Cartridges cost £5-£15 each.
- Multi-sized cone spanners: 13, 14, 15 and 16mm
- Open-end 15mm spanner
- 5mm Allen keys
- Solid rear axle
- Nylon mallet
- Small screwdriver
- Bearing grease
- Special tools or alloy tube to press the bearings
1 Remove the adjuster nut on the skewer and lay the bike flat with the exposed thread pointing up. Apply a shot of penetrating fluid and let it soak for a while. Repeat a few times, then reinstall the nut and give it a firm whack with a nylon mallet. This should free it enough to move the wheel past the safety tabs. Now spray some fluid in the other side and work the skewer back and forth with the mallet until you can yank it out by hand. Slip a 13mm cone wrench behind the locknut then, using the correct spanner, position yourself safely and loosen anti-clockwise.
2 Carefully pull out the axle assembly over a cloth to catch any stray parts or bearings. You’ll probably want to remove the dust caps to make access to the cups easier for cleaning purposes. This might be a little tricky, as it requires you to gently pry them off using a blunt screwdriver or tyre lever, applying gentle pressure around the inside of the cap. Sometimes they’re deformed in this process, which means they become more difficult to fit. If they prove really stubborn and you don’t want to risk damage, you can just work around them.
3 Remove the bearings with a small screwdriver and clean them for inspection. You should spot any damaged or pitted balls and cones. As the quick-release tightens, it compresses the cones and bearings beyond their ideal adjustment, which causes premature wear and pitting. These tiny potholes or irregularities are the cause of your noisy hub. If you notice cratering in the cups, you’ll need a new hub, which usually means a new wheel: it’s only when you have a high quality rim that it’s worth rebuilding. Ask your local shop for advice.
4 Clean and flush out the cups with a spray degreaser or a bit of white spirit or citrus degreaser. Wipe and dry everything. Now put a dollop of new grease in the cups, enough to hold the bearings in place while handling the wheel. If you’re unsure of the quantity to use, (usually 10 or 11 3/16in bearings), just fill the entire cup until they touch, then remove one. After installing the bearings, reverse the removal procedure: gently tap the dust caps back in and reinsert the axle assembly, being careful not to dislodge the bearings.
5 The axle should turn freely, but without significant play – a bit is good, though, because the quick-release clamping force adds load to the bearings. Start by tightening the locknut firmly against the cone on one side of the axle. You’ll be fine-tuning with the other side. Bring the moveable cone finger-tight against the bearings, then the locknut. Hold the cone and tighten the locknut firmly with the 15 or 17mm wrench. Test this. If it’s too tight, back off the cones with two 13mm spanners while forcing the locknuts tight, creating some play.
1 The axle will probably have at least one end with a removable dropout guide/locknut, which you’ll need to take off. In most cases, this can be done by inserting a 5mm Allen key at both ends and turning anti-clockwise. You might have to put some muscle into it, so use a little cheater bar or long keys for this. Keep track of any washers and their positions between the spacers and axle. The silver spacer doubles as both dust cap and decorative element in most hubs. It might take some strength to pry off; it will likely be held by a rubber O-ring between it and a groove on the axle. Alternatively, some hubs (eg. Mavic) have a threaded cap to allow for bearing adjustment, so just unscrew these first.
2 In order to remove the cartridge, you’ll first need to support the hub in such a way that you won’t damage it. For example, you could use a delrin tube of the sort you can pick up from Hope. You’ll need to strike a few sharp blows to get the cartridge out, so a rubber mallet probably won’t do; a resin mallet or a hardwood block with a lump hammer are much better at delivering the force necessary to dislodge it. It’s also important to avoid whacking your axle from the side without buttressing the hub using the special tool for the job (as shown on the far left of the image above). After all, you don’t want to damage your axle and spokes, do you?
3 The next operation removes the bearing left behind. Flip the wheel over and position the hub with the bearing facing down. Make sure the hub is sufficiently supported by the flange and there’s room for the bearing to come out. Carefully position either the axle or a suitable drift tool (an aluminium tube or even an old solid axle with a cone or nut threaded partially onto it) and knock the bearing out with a few sharp blows. Be aware that you might have to hit it pretty hard if it’s a tight fit. Clean with degreaser and a rag, including the hub flanges around the spoke anchor points, and inspect for cracks or corrosion. You’ll need a new hub or wheel if cracks are spotted.
4 Spread a light coating of grease or oil on the contact surfaces (the outside and inside of the new cartridges, the hub bearing cup and the axle). If the grease is too thick between the bearing and the hub, it could prevent it from seating completely. The new bearing should only be driven using the outer race. Use the old bearing or a socket of exactly the same diameter. Keep in mind that the bearing races are made of hardened steel and are therefore potentially brittle. Wear protective goggles and make sure the contact area between the drift edge and the outer race edge is maximised by being perfectly aligned. You’ll know the bearing is seated when the blows suddenly firm up.
5With the first bearing side down, slide in the axle from the inside. Position the second cartridge on top and using the appropriate drift tool, drive it in with a few careful mallet or hammer blows. Don’t allow the bearing to go in askew. Attempting to force it in if it’s badly out of line will only get it jammed and make it harder to install, creating ridges that could prevent it from seating correctly. Thread the dust caps or slide spacers back on with a little oil, then feel for buttery smoothness. If it’s tight, strike a couple of blows on the opposite end (the end inserted first into hub). This should balance out the bearing load and smooth it out. Ride on, brothers and sisters!
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