Ebay has rear irs bearings for $26 a set. If you are getting rumble noise from there while driving, then you know they are worn, otherwise look out for dirt, Brinelling (
http://en.wikipedia.org/wiki/Brinelling) etc.
For what they are worth, if there is any doubt, just slap on a new fresh set.
There are spacers.
And the bearings are easy to take out. Tap the stub axle out, remove the big circlip that holds them in, then tap the bearings out with a hammer as they are pressed in. You will see the spacers on either side, make sure to write or record the orientation they face (facing in or out etc). Permanent marker on the spacer or sumfin will do.
Look for wear on the stub axle to make sure the bearing hasn't spun (like a groove or indentation that you can feel with ur finger nail where the inner part of the bearing sits.
OH! and have plenty of rags :P Don't be afraid to give them a decent whack out... a mallet might be better, or a thick rag over the tip of the hammer to prevent damage to the stub axle.
To press and knock out the bearings you will need to use a socket and extension.. with the socket sittin on the bearing and give it a good knock.
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