I have noticed a few comments from people on replacing wheel bearings when putting on new rear tires - is this an issue I should be looking out for? Reason I ask is that the drive belt does not always stay at the same place on the rear pully no matter how well I adjust it and different tension doesnt effect it - wanders 3-5 mm when I stop to check at different times - could that be wheel bearings or swingarm bearings going bad?