Trailer Maintenance: Tire Pressures And Wheel Bearing Grease

Published: December 4, 2013; updated: December 4, 2014

Trailers do not need much maintenance, and the maintenance they do need is straightforward. You need a couple of tools that you may not already have, but nothing extraordinary. Maintaining your trailer will spare you from having to change wheel bearings at 3 am on a rainy night en route to an event.

Tire Pressures

In my experience trailer tire blowouts were caused by insufficient tire inflation pressures. Trailer tires are typically rated to hold their stated load at about 55 psi. One time after I experienced a blowout I checked inflation pressure on remaining tires and one was at 21 psi!

How much weight a tire can support is a function of its inflation pressure: more pressure equals more weight. My trailer is rated for 7,000 lbs gross weight. It has four tires each rated for 1,860 lbs at 55 psi. My actual trailer weight is about half that - a car weighing 2,400 lbs plus the trailer itself weighing about 1,300 lbs. I can run a bit lower than maximum tire pressure and blow tires. A trailer loaded to the maximum has much less leeway.

Another issue with trailer loading is uneven weight distribution. This is less of a problem for open trailers that just have a car on them which can be moved back and forth, and more of a problem for enclosed trailers where the car inside is restricted to a portion of the trailer and the remaining space can have varying amounts of tools and supplies. Uneven weight distribution means that even though the total trailer weight may be under the gross rating of the trailer, individual tires can see larger loads than they are rated for. In these cases especially it is very important to regularly check trailer tire pressures.

Tools Needed

You need an accurate pressure gauge. Most of the cheap gauges sold in auto parts stores are either inaccurate from the start or lose accuracy with age. If you have more than one gauge, check pressure of the same tire with both - chances are, they will read differently. If not, borrow a gauge from a friendly competitor at your next event for this experiment.

Higher quality racing pressure gauges are typically more accurate.

The second thing you need is a source of air. Because you typically need to inflate trailer tires to 50+ psi, you will need either a full air tank or an air compressor.

An efficient way to fill up trailer tires is to use air available at race tracks - before you leave, pull up to the hose and enjoy free air.

Spares

You should have a spare tire for your trailer. Open trailers apparently more often than not do not come with a spare. I asked the dealership where I bought the trailer for a spare, and they sold one to me on the spot. Alternatively etrailer.com has wheel and tire assemblies for sale, as does Amazon.

Etrailer sells a number of spare trailer mounting brackets. I bought this Fulton one which is offset for additional ground clearance for the wheel. It works great and I wish I bought it sooner. Digging trailer spare from the very front of the truck box filled with stuff is silly when the bracket costs $30. Plus, you get that bed space back.

Be sure to inflate the spare when you check pressures on the trailer tires!

Wheel Bearing Grease

The second most common failure point on trailers is wheel bearings. These need to be greased periodically. How often? Good question.

I had my first wheel bearing failure 2 weeks into my ownership of the trailer, and it was fixed by the trailer dealer. Then I towed the trailer for about 2 years without any issues without ever greasing the bearings. Then I started having repeated wheel bearing failures, including ones on wheel bearings that were recently replaced.

Nowadays I try to add grease to the bearings every month or so.

Tools Needed

First, you will need a grease gun. The cheapest one with a fixed neck will generally work for adding grease to trailer axles, although for adding grease to tie rods and suspension components on cars you will need one with flexible hose.

Then, you will need grease. I use the "high temperature" grease for "drum and disc brakes" that comes in 14 oz tubes. Trailer supply stores also sell marine grease that is supposed to be better at repelling water.

Finally, you will need a tool to remove and replace the hub caps. If you have EZ Lube axles, they have a rubber cap that you can pry off with a flat head screwdriver. For non-EZ Lube axles you will need a hammer and a flat head screwdriver or - my preference - a flat punch. You will want the caps to stay on the hubs, which typically necessitates hammering them back in place. If you can put the cap on the hub with only the force of your hand, the cap can fly off once the trailer is moving and the hub heats up - ask me how I know.

Spares

You should have at least one complete wheel bearing kit with you at all times. Replacing the wheel bearings is straightforward for any mechanic, but figuring out which bearings you have is a long and often expensive process. If you do have spare bearings, plenty of people at the track can change them for you.

It also helps to have a spare drum. Prepare it by installing the inner race, bearing and seal into the drum at home, as well as the outer race. If you do have a bearing failure, all you need to do on the road is remove the old drum, put the new drum on the spindle, then install the outer bearing into the drum, install the axle nut and grease the bearing. This can easily save an hour of roadside repair time.