And if you own a trailer, youa#39;d better treat them as such. Wheel bearings allow a wheel to turn without creating friction that would completely trash a wheel and axle. Most trailer wheels have a set of bearings on the inside of the hub and another on the outside. They are seated in races on the ... If light problems occur, the tester will help you pinpoint the problem quickly. To be safe and legal, a trailer mustanbsp;...