Rear Bike Hub
Since rear hubs and wheels cost more than fronts, and because the rear hub comes loose more often, it is important to frequently test your rear hub. Hold the rim with your fingers, and try to move it laterally. If the hub moves in any direction other than rotating, or if it is too tight to rotate freely, it needs adjustment. But if it wiggles, first see if the problem is a loose quick release or axle nut.
The rear hub is like the front hub, except the gears are attached to the rear, so they are more complicated.
Rear Hub Adjustment
Tools needed to adjust a rear hub:
2 cone wrenches, usually 15 mm (cone wrenches are thinner than ordinary wrenches)
open-ended wrench for the locknuts, usually 17 mm
The procedure to adjust a rear hub:
1. Read the introduction to bicycle hubs. Refer to the section on front hubs.
2. Take the wheel off the bike and remove the quick release device or axle nuts.
3. Remove any rubber dust covers from the outside of the locknuts. Clean everything you can reach.
4. Examine the hub and axle to try to diagnose the problem. Are the locknuts loose? (They should be tight.) Does the axle wiggle when you move it? (It should not. You will need to tighten the cones.) Will the axle rotate freely without grinding or catching? (It should. You will need to loosen the cones.) Is the axle bent or broken? (You will need to replace it.) Does it feel dry or gritty? Has it been submerged in a creek crossing, washed with a pressure hose, or engulfed in mud or sand? (It probably needs an overhaul.)
5. If the locknut-cone connection on the drive side is obviously tight, you may not need to remove the cogset. The drive side will be the first-tightened side, and you can start with the fine adjustments on the other side. Follow the procedures under front hubs, starting at step 6.
6. If you can put your cone wrench on the drive side cone, you may not need to remove the cogset. (On some freewheels and most cassettes the cone wrench won't reach the cone on the drive side without removing the cogset.) The drive side will be the first-tightened side. Follow the procedures under front hubs, starting at step 4.
7. If the drive side locknut-cone connection is not obviously tight, and you cannot reach the drive side cone with your cone wrench, remove the freewheel or cassette. Clean everything you can reach.
8. If you have a freewheel hub, follow the procedure under front hubs, starting at step 6. Make the first-tightened side the drive side. You want the drive side to be the tightest. The next time the hub needs adjustment, you won't have to remove the freewheel if the drive side is tight.
9. If you have a cassette hub, life is more complicated, because the freehub body is in the way of your cone wrench on the drive side.
a. Loosen the non drive side first. Break the lock between the locknut and cone: hold the cone steady with the cone wrench, and loosen the locknut with the open-ended wrench by rotating it counterclockwise. Move both the locknut and cone outside (counterclockwise) far enough for you to be able to work on the drive side cone. (You may have to completely remove the cone, but try to leave it on.)
b. Now that you can reach the drive side cone with the cone wrench, follow the procedures under front hubs starting at step 6. Make the drive side the first-tightened side, and snug it up real tight. The next time the hub needs adjustment, you won't have to remove the cassette if the drive side is tight.
10. Replace the cogset.
11. Return the wheel to the bike, and check brake and derailleur adjustments.
Rear Hub Overhaul
A rear hub overhaul is like a front hub overhaul, except you have to remove the cogset. Remove the cogset and follow the procedure for front hubs. Be extra careful to remember the order of the cones, locknuts, and spacers. As you take them off, slip them on a screwdriver to preserve the correct order. Also, on some cassettes, the number of ball bearings on each side may not be the same, and their sizes might be different.