Volvo S60 T5
Swopped my wheels front to rear the other day, cause im a tight git and want my tyres to last as long as possible, And noticed that on the rear hub bearings the caps had been left off from new, this allows water and dirt to get into rear bearing.
Could potentially be a safety issue so check this:
Remove the rear alloy wheel nut cover and if you can see the hub nut I suggest you get down to your dealer to have them fit a dust cap if your is missing.
http://erc.qmuc.ac.uk/cliosport/gallery/full/1068393327__rearhub.jpg