Off-road trailer guide

Setting the correct tyre pressure and ongoing checks and maintenance are part of any trip. Identifying a developing issue is better than addressing a catastrophic failure in remote Australia, where parts are hard to get, recoveries expensive and ruined holidays unpleasant.

Correct tyre pressures

Setting the correct tyres pressures on your trailer is part art and part science. A higher tyre pressure is used on bitumen and a lower one off-road to allow the tyre to flex over stones, corrugations and rough surfaces.

My trailer has matched rims and tyres to the Nissan Patrol, so they can be interchanged. In a real emergency the trailer can be cannibalised to keep the car running. There is one spare on the car and another on the trailer. The spares can be used on the car or the trailer. I also carry a puncture repair kit.

The tyres are Coopers ST Max, which are a light truck construction, a heavy build quality than standard all terrain tyres.

The Trailer Manufacturer’s suggested tyres pressures were too high with the Coopers ST Max fitted and created a rough ride in the trailer and a broken gas bottle holder because of corrugations. What tyre pressure is set depends on:

1. tyre type. The Coopers ST Max allow a lower pressure to be used because of there construction;
2. fully loaded weight of the trailer. Mine would rarely go above 800kg, so it is light for a trailer;
3. the road conditions. Rougher roads will mean lower pressures.

That’s the science, now the art. When setting the pressures I also look to ensure the tyre is bulging (a technical term!) to a similar extent as the tyres on the fully loaded car. This will mean a lower pressure on the trailer but a similar amount of give to the tyres on the car.

For my trailer the art and science tells me to set pressure at 12psi (cold) for off-road and 16psi (cold) for bitumen. You should vary tyre pressure as the surfaces change, although a brief change in surface does not require a change.

If you are unsure of what pressure to use, start at the recommended pressure and reduce by amounts of 2 psi until you find the sweet spot. I started at 26psi and ended up with the range of 12 to 16psi.

Ongoing checks

In comparison to cars, trailers are neglected, perhaps because no inspection is needed to renew registration on lighter trailers (some trailers do require annual inspections). Here are the checks I do, often during a break from driving:

• shocks and springs;
• is the trailer level?;
• are the lights working?;
• check tyre pressures to ensure tyre pressure is maintained;
• check wheel nuts are tight. The Doc use a torque wrench set to 120 foot pounds to tighten the wheel nuts (the same setting is used for the Nissan Patrol);
• check the bearings. Put on gloves, place a hand on either side of the tyre and firmly push back and forth. It there is movement, the bearings may need to be adjusted. Tip: know how to adjust your bearings before you go on your trip. Luckily for me an experienced person helped out on the road;
• use the back of your hand to feel the heat on the hub, then compare to the other side. If there is a material difference, there is probably a problem with the hotter hub. Monitor closely;
• check the towing hitch. Follow the Manufacturer’s maintenance requirements (something we often forget). DO35 User Guide here.

Adjusting bearings

Adjusting the bearing in the hub is not hard. You can access the hub more easily if the tyre is removed. Use a small cold chisel and hammer to separate the hub cover from the hub. Be firm, but not forceful. You will see a split pin holding the nut in place. The nut is called a castellated nut, because it looks like “the crenellated parapet of a medieval castle.”

Carefully remove the split pin (have spares). Adjust the nut as required (normally by tightening). Align the hole in the bolt with the next slot in the nut, reinsert the split pin. Open the split pin again. Replace the hub cover. Double check hub cover is firmly in place. Tip: if you break the split pin and do not have spares, try and use a nail or wire as a temporary fix.

Once the bearing is adjusted, put the tyre back on and rotate the tyre to ensure it is not too tight. Readjust if necessary. Check for heat build after the adjustment closely to ensure the bearing was adjusted correctly.

Sometimes you may need a shim or spacer to properly adjust the bearing, this is beyond the scope of this guide.

Manual

Make sure you read any User Manual you received with the trailer and follow the checks and servicing requirements listed in it. For example, a DO35 off-road hitch needs to be greased every so often.

Driving for car or trailer?

The suspension, ride and performance of a car differs from a trailer. Cars seem better suited to rough roads than trailers. This means you may need to alter your driving style to suit the trailer, even if that means a rougher ride in the car.

Regardless you need to drive the car and trailer with mechanical sympathy. Mechanical sympathy, for me, means not running the car at or near 100% of its capabilities for long periods, so:

• give the driver and the equipment regular breaks (mostly so the tyres and suspension can cool);
• do not drive too fast for the conditions. The harsher the conditions, the slower you drive. Many people do not allow enough time and speed in Outback Australia;
• service the car regularly. Most car manufacturers recommend a more comprehensive service schedule for cars used in harsh conditions.

Miscellaneous

Remove the jockey wheel from its bracket and store it in the toolbox or trailer. The corrugations over time will damage or break the bracket. Or leave it on and have it break the bracket or worse fall off without you knowing.

Other brackets that store jerry cans or gas bottles should also be checked for damage.

Equipment needed

• hammer;
• small cold chisel;
• pliers;
• small metal file;
• something clean to place the parts when you are working;
• torque wrench (also used for the Nissan Patrol wheel nuts);
• a rubber mat to kneel on; and
• jack and wheel brace if removing the tyre.

Spare parts to carry

• spare rim and tyre for the trailer;
• puncture repair kit (one will suffice for the car and trailer);
• split pins compatible with your trailer;
• a spare bearing; and
• axle grease. Tip: one trick is to store the bearing in the axle grease container. That way the grease is already packed into the bearing when needed.

What spares you take should be governed by the length of your trip, how remote you are going and the ability to source parts. If your trailer uses rare spares, you need to carry them.