The rear hub adjusts the same way as the front one, but the job is complicated by the cassette that is attached to the back wheel.
You must remove the cassette to service the rear hub. One complication is that the right-hand cone is recessed into the freehub body, forcing you to make adjustments from the left-hand side. The most common spanner sizes are a 15mm cone spanner and a 17 mm ordinary spanner, and 181/4 inch ball bearings. The rear hub needs servicing more often than the front: the rear wheel is forced around by the pedals and it carries more of your weight, so works harder. It’s also too close to the drivetrain for comfort, lying first in line for debris flying from your chain. The right-hand side can be messy. Service it frequently for best results and always replace bearings when you service a hub. If the cups in the hub are badly pitted, think about replacing your hub. It’s often best to take the wheel to your bike shop for an opinion. One option is to buy a new hub and spokes and rebuild your wheel around a new hub. See the wheelbuilding section for instructions. Once you’ve removed and cleaned the dirty stuff, wash your hands so you can fit things back together without contaminating the bearing surface.
Step 1: Remove the wheel and the skewer. Peel off any external seals covering the cone flats. It’s best if you can do this by hand – pinch the seal between two fingers to release it, then pull. Otherwise, slide a screwdriver under the edge of the seal and twist. Check the condition of the seal and replace if the edges are cut or torn.
Step 2: Hold the left-hand cone still with your cone spanner, and loosen the left-hand locknut with your locknut spanner. Remove the locknut completely, then any spacers. Hold the spanners so that your hands move apart as the locknut releases – it often gives suddenly and will trap your fingers painfully between the spanners. Be careful.
Step 3: Swap the lockring spanner to the righthand side of the wheel and use it to hold the axle still while you wind off the left-hand cone completely. Line up the parts as you go, so you can replace them in the right order, the right way around. Draw the axle out from the right-hand side of the wheel, catching any bearings that come out too.
Step 4: Clean axle with the right-hand parts attached, along with the parts removed from the left-hand side and the bearing surfaces inside hub. Wrap some rag round a screwdriver tip to get bearing surfaces clean. Use bike wash or degreaser for stubborn bits, but rinse and dry the hub afterward. Inspect the bearing surfaces. The bearings will have worn a track on both cups and cones, which is fine, but it should be smooth, with no pits. Replace pitted cones.
Step 5: If you’re replacing a right-hand cone, note how much axle sticks out the end of the lump of cone, spacers and locknut. Hold cone steady on axle with cone spanner. Use the lockring spanner to remove the lockring. Wind old cone and any spacers off axle. Wipe axle clean and refit new cone. Refit spacers, then wind lockring onto axle to same position as before. Hold locknut still and firmly tighten cone and lockring against each other.
Step 6: Put enough grease into the cups on each side of the hub so the bearings sit in grease up to their middles. Pop into each side as many bearings as came out. There will always be the same number in each side, and it’s usually nine. If you push a bearing into the cup and another one pops out, you don’t need another bearing.
Step 7: Slide the axle, with the right-hand cone and lockring firmly tightened on to it, carefully into the hub from the right-hand side, making sure you don’t dislodge any bearings. The cone will probably disappear completely into the hub.
Step 8: Thread the left-hand cone onto the end of the axle that’s sticking out from the left-hand side, and tighten it down by hand so that it touches the bearings but can still spin freely.
Step 9: Refit spacers in order, followed by the locknut. Tighten the locknut down by hand so it wedges against the spacers, then use the two spanners to tighten the cone and locknut together so that they wedge firmly onto each other. Test the adjustment – it is rarely right first time. The axle should spin freely with little resistance.
Step 10: Hold the wheel so that the end of the left-hand side of the axle faces towards you and rock the axle from side to side. There should be no play at all – you should not be able to feel the axle knocking from side to side. If the adjustment isn’t correct, hold the left-hand cone still and undo the left-hand lockring a turn.
Step 11: Hold the axle still with a spanner on the right-hand lockring and adjust the left-hand cone – clockwise if there’s knocking, to reduce the space between cups and cone, and anticlockwise if the axle is stiff, to give the bearings space to spin freely.
Step 12: Holding the left-hand cone in its new adjustment, tighten the left-hand locknut against it. This often changes the adjustment, so play with the adjustment to compensate – a satisfactory adjustment often takes several goes, but it’s just a case of trial and error. Once you’re happy, replace any seals and refit the cassette and skewer. Refit the wheel, tightening skewers firmly.
Tools for adjusting front cones
- Cone spanner – almost always 13 mm
Tools for adjusting rear cones
- Cone spanner – almost always 15 mm
- Locknut spanner – an ordinary 17 mm spanner will work on most – however, those locknuts with two flats rather than six will need a 17 mm cone spanner
Tools for servicing hubs
- Spanners for hubs as above
- Good-quality bicycle grease, for example Finish Line or Phil Wood
- Degreaser and clean cloth to clean hub surfaces
- Replacement bearings – almost always 3/16 inch (5mm) front and 1/4 inch (7 mm) rear – if in doubt take your old ones to the shop to size-up fresh ones
Source : BIKE MAINTENANCE TIPS, TRICKS & TECHNIQUES
See also bike maintenance tips, tricks and techniques “Cup-and-cone hub service: front”