The biggest mistake the average boater makes when replacing wheel bearings on his trailer is just putting grease in the wheel hub and not into the bearing. It’s got to get into the bearings to work right. Otherwise they start burning up again right away. In order to get the bearing properly covered with grease, you've got to keep rolling them in your hand with a good dob of grease, working it back and forth until it’s jam-full from both sides. The grease has to come out all around. You've got to spin all the needle bearings, the race, everything to make sure they’re all covered with grease, inside and out. And another thing. You've got to replace the race and the seal every time you replace the bearings. Never use an old race or seal with a new bearing. They've been worn to match each other, and you’ll never get the right fit.

Are bearing protectors are recommended? YES - they're the best thing to come along in years. They tell you when they're full of grease, and they help keep the water out. But you still have to be carefull. Pump too hard and you'll likely blow out the seal at the back. And you still have to check them periodically. Give them a squirt of grease to push the water out.

How do you know how far to tighten the axle nut over the wheel bearings? Tighten it down all the way, until it’s tight against the bearings, then back-off a half-turn. What you want is to be able to spin the tire so it goes around five or six times before stopping. If it spins too much, the nut’s too lose. If it doesn’t spin at all, back it off some. You don’ want too much pressure on the bearings or they’ll fail prematurely.

How much grease do you put in with the wheel bearings? Pack them in chock full, after filling the inside of the hub as best you can. If your old bearings were shot, you've got to try and get as much of the old grease and metal pieces out as possible. Then fill the cap with grease, smear some into the hub, put in your bearings, and cover them with grease. Fill the hub cap with grease, tap it on, and get on down the road to the launch pad!

(with thanks to Dan Armitage and Robert Connelly)