Power at Work: It pays to look after your trailer wheel bearings

Thursday, June 10, 2010

Doing the necessary checks and using the right grease are maintenance musts to keep your trailer in good working order

by KEITH BERGLIND

Every time I see a bad set of wheel bearings or a bad wheel bearing set-up, I feel compelled to write a fresh set of instructions. "When will everyone catch on?" I ask myself. Well, one reason is that jobs are changing, cars last longer and there are more trailers on the road.

Years ago, mechanics routinely serviced the front wheel bearings twice a year, plus every time the front brake shoes were replaced. We got lots of practice. These routine jobs are gone and I suspect now that a lot of repair guys are just not properly trained.

The rear wheel bearings of a front-wheel drive car should be serviced every year, or at least whenever the front brake pads are replaced. Please don't wait until the bearings fail.

Trailer wheel bearings are the new "must do" at a regular time of use. These years, I put a lot of miles on my RV trailers, from the fifth  wheel to my little Boler trailer. The first year, I pulled the fifth wheel all over the west and south to Mexico and learned that these things are not perfect and that many trailers require a lot of precautionary checking. I've seen too many dead trailer axles out behind RV trailer shops.

Currently, a trip home from down south is over 4,000 kilometres, and I've found that I can't trust the trailer bearings to stay in shape that long, so I routinely jack up each wheel at one-half the way home and check for loose bearing play. This job only takes a few minutes at a rest stop or a Wal-Mart lot.

Here are two quick main checks you can do.

•    Spin the wheel and listen for unusual bearing noise.

•    Grasp the wheel, top and bottom, and rock the wheel.

   I only want to feel the slightest of free-play.

If I already did this check before I started the trip, I should be able to feel the same amount of play at every check point. It's only when the free-play increases that I have a problem which may need to be checked.

Now may be a decision time. If the bearings turn quietly, but there is a bit more free-play, I probably will pull the dust cap, pull the cotter pin and tighten the slotted nut one notch only.

Now I repeat the two tests. If I'm satisfied that the bearings turn quietly and freely, and that the top-bottom rocking free-play is reduced or gone, then I put the dust cap back on and remove the axle jack.

There is a common reason for many trailer axles to develop loose bearings in a short distance. I have seen cases of spindle wear where the large inner wheel bearing turns on the spindle and wears its way into the spindle.

For now, I will leave that problem to another article, where I will address how I deal with and stop this wearing action.

So what grease should you use? Every time I see a guy greasing wheel bearings, I look at the can of grease. Read the name and the label statement of use. It must say "Wheel Bearings," or some such language. New greases now specify for use with disc brakes. Many vehicles with disc brakes can be driven very hard and that leads to excessive heat in the brakes and wheel bearings.

We no longer have one grease for winter and another for summer. I just use the highest rated wheel-bearing grease I can buy. It doesn't pay to buy a large can, because a small can last for years, and I prefer to upgrade occasionally to the latest formula.

Most cans of grease get used for other jobs and it's not unusual to see an open can of wheel-bearing grease sitting on a bench or shelf, collecting dirt, especially from a mechanic's dirty fingers.

Never use "gun grease." If it comes in a tube, labeled "General Purpose," don't let it near a wheel bearing. Some guys with a casual approach to greases will tell you that they always use their can of "red grease" or "blue grease.," I prefer to go by what's on the can label.

The basic wheel-bearing adjustment rule for a pair of opposed, facing tapered wheel bearings is that the running clearance should be zero at peak operating temperature.

So, if you start cold and loose, this loose clearance will be less at operating temperature. And if you start cold and too tight, the bearings will run tighter yet, when hot.
More on this next time. BF

Keith Berglind is a licensed heavy-duty mechanic.