This is a quick service job on a 20mm DMR Revolver through hub. The bearings are sealed so replacement is required when you hub starts to sing to you on a quick downhill section.
Do not assume that your local bike shop will hold stock but the manufacturer’s site will normally state the size and some show simple instructions for changing the bearings. The main internet suppliers will reply to a query about size and even offer you a part code.
If you are really keen then there are some sites which delve into bearing nomenclature and the delights of hoop stress and radial stress. Please allow me to bore you with this individually on a ride.
I fitted the external cups and gently pressed the bearings fully home. The manufacturers instructions suggested using the socket and hammer method but this seemed harsh. I did consider using a drill press or a vice but the correct tool is a bearing press. I used this ratchet clamp as a substitute.
Everything was cleaned and regreased at the appropriate points.
A quick service job that is less difficult than cup and cone as all the worn bits get replaced as a unit.