How do I check the wheel bearings and brake drum on a trailer?

Check the wheel bearings: Jack up the wheel, hold it at the top and bottom and wiggle it, then turn the wheel. A very slight amount of play, just noticeable to the touch, is normal. Significant play, grinding noises or rough running mean you should check the bearings and, in most cases, replace them.

With tapered roller bearings, the play can be adjusted via the axle nut. Compact wheel bearing units are not adjustable and must be replaced in their entirety.

Grease: With conventional tapered roller bearings, the grease is replaced at longer service intervals — wash out the old grease, check the bearings, and refill with new grease. Contaminated or water-contaminated grease is the most common cause of bearing damage, particularly on boat trailers.

Brake drum: When opening the brake, check for cracks, grooves and the internal diameter. Drums that are severely worn or have a blue tinge (overheated) must be replaced. A warped drum will also be noticeable — the trailer will then brake in a pulsating manner. Wipe out brake dust rather than blowing it out.

Rule of thumb: Whenever you change the brake shoes, check the bearings and drum at the same time — the wheel hub is already off, and removing it a second time takes longer than the cost of the spare part.

Replacement: Wheel bearings and brake drums.