Bearings on unicycles generally last a long time; even when you take your unicycle in a fountain, or the sea, or just splashing around in the mud. They do give up in the end though; normally at the worst moment possible. You hear them grinding first, then when you turn the wheel slowly by hand you can feel the restriction in the movement.
What you will require:
Replacement bearings - see here for quality replacement bearings, Crank extractor and bearing puller - again we sell these. Pedal spanner, 14mm Socket or 8mm Allen key, Rubber hammer/mallet and some cut of sections of seat post.
To remove and fit bearings:
1. Remove the dust covers from the cranks (if you have them).
2. Remove the nuts/bolts from the centre of the cranks
3. Remove the cranks using a crank extractor. (Be sure to screw the extractor fully home before you start to extract the cranks).
4. Remove the wheel from the frame, in most cases this involves removing 4 bolts from the bracket that surrounds the bearing.
5. Fit the bearing puller over the bearings and use a spanner to pull the bearing from the hub. Be sure to seat the legs of the bearing puller securely under the bearing so that it is not destroyed before it is removed from the hub. For ISIS hubs use the ISIS cap from the crank extractor to prevent the bearing puller damaging the threads in the hub.
6. Once both bearings have been removed clean the hub shaft with wire wool and little oil to remove any rust or dirt.
7. Fit new bearings over the shaft (be sure to fit spacer on first if one was fitted) and gently push, ensuring that it is square with the shaft. When it can not be pushed any further on by hand, slip an old piece of seatpost over the shaft on both bearings (Ensure that the Old seatpost is pressing on the centre of the bearing, not the outer ring or rubber seal). Place the wheel on a solid surface or floor. Hit the old seatpost with a hammer until bearing is seated home (see pic below)
8. Clean the bearing holders to be sure that there is no dirt or rust.
9. Re-fit the wheel in the frame. Be sure not to over tighten the bearing cups as this will impede the performance of the bearing.
10. Re-fit the cranks on the hub. Be sure to check that the cranks are on the correct side. There should be an L or R on the cranks to indicate which is which.
12. Tighten the crank nuts/bolts these must be secure. Tighten well but do not over tighten.
13. Replace the plastic dust caps (if you have them).
14. Go for a ride :-)