I did a thread on how to change a set of taper roller bearings recently and Nick Hearne asked if I could do one the next time I changed a set of 'sealed for life' bearings, so here you go
I recently did a service and bearing change for Steve Hall (member on here) and he generously agreed to let me post some pics up for everyone's benefit.
Anyway, 'sealed for life' (SFL) bearings are a bit of a misnomer, as they're certainly sealed, but not to the exclusion of water ingress. They're fantastic bits of kit for cars and caravans, but not so good for trailers that get dropped in the drink on a regular basis. In my experience, even the ones labelled and advertised as 'waterproof' generaly aren't.
So if you run SFL bearings it's still advisable to check them on a regular basis - listen for rumbling, check for overheating etc. One of the down sides of SFL bearings is that you can't easily service them, i.e. strip them, clean them, repack with grease and reinstall them. If they're gone, or going, it's best just to replace them....
So remove the drum; usually a large hub nut, with no split pin. They're generally done up to around 280Nm, so make sure you do some press ups in the week leading up to it. Then remove the rear circlip (a pair of ratcheting circlip pliers are useful):
Then flip the drum over and press the bearing out from the front, pressing towards the rear / back of the drum. Place a large socket between the press and the bearing face, so it distributes the force more evenly:
Then you'll have the bearing out (on the left) and the new one to go back in (one in the oiled, protective wrap on the right):
Then just do the reverse to install the new ones. Easy as that! With the one shot nuts (no split pin) make sure you replace it too when you replace the bearings.
If you haven't got a press lurking about then you can (though it's not pretty or quiet) replace the bearings by giving the socket, you've put on top of the bearing, a ruddy good thump with a large hammer. It's not ideal, as it's possible to damage the bearing, but if you're in a pinch it may be the only option.