Please note that this will be updated with more information from time to time.
By Mike Ilsley
No matter what the sales person told you, you must expect that the “featherweight, easy to tow” trailer is going to act like an anchor off road. There are several things to consider when towing off road. All the on-road aspects apply, but some special circumstances must be catered for when towing off road.
If one was to choose a main theme around “selecting a trailer”, it must be, select a trailer which firstly matches your vehicles towing capabilities, and then only secondly which fulfils your wish list. This means selecting a trailer that has a similar track width as the tow vehicle and that is within the towing mass limitations of the tow vehicle.
Before going further, one further piece of advice, choose the lightest trailer you can, as long as it is well constructed, you won’t be sorry!
As with a 4x4 vehicle, which has a break over angle under it’s belly, the vehicle/trailer combination has an additional break over angle between the rear wheels of the tow vehicle and the trailer wheels. The difference is that this break over angle will constantly change as obstacles are negotiated and the trailer and tow vehicle twist, turn and bump up and down.
Similarly, the trailer also has a departure angle, which must be considered when off-roading.
But there is one more critical aspect and that is the fact that the trailer is hinged to the vehicle. This means that the distance between the front of the trailer and the rear of the tow vehicle is constantly changing, and negotiating deep ditches or “dongas” can force the trailer to collide with the tow vehicle due to the trailer being raised too high in relation to the tow vehicle or the nose of the tow vehicle climbing a very steep incline.
Care must also be taken not to turn too sharply as the trailer can “jack-knife” into the back of the tow vehicle.
A trailer that has a similar track width to the tow vehicle will allow the trailer wheels to follow in the tracks of the tow vehicle most of the time. However, off-road one will often encounter sharp turns. The trailer will follow a smaller turning circle. This means that, different to when travelling in a straight line, the trailer wheels will not follow the tracks of the tow vehicle, but will be to the inside of the turn. As a result, the trailer wheels can easily hit objects at the side of the trail, damaging the tyres and even breaking the axles or springs.
To overcome this, the tow vehicle must turn wider than normal, sticking to the extreme outside of the trail, allowing sufficient room on the inside for the trailer wheels. This in turn again exposes the front wheel of the tow vehicle to damage, so lots of care must be taken over this aspect as well.
These things all mean one thing, towing a trailer requires a huge amount of extra care and concentration.
Tip: Drive slower with the trailer and make sure you leave enough room to manoeuvre.
These days it is incorrect to speak about the weight, it is the mass of the trailer. When considering a trailer, take special note of the D/T rating of the tow vehicle. This figure may not be exceeded by the total towed mass. This means the mass of the empty trailer plus the entire load of the trailer.
But spare a thought for the poor tow vehicle. For example, let’s say that the D/T rating on the tow vehicle is about 4 000 Kg. Now when towing on road, this is already a major load and the vehicle has to work very hard to pull away and stop with this load behind. A large off-road trailer can have a GVM (Gross Vehicle Mass) of 2 500 Kg, when it is fully loaded, On paper the tow vehicle can handle this load fairly competently on dust roads and tracks, but as soon as any deep sand is encountered, that’s the end of the story. Even with the tyres on tow vehicle and trailer deflated, you are going to get stuck, badly. Not only that, towing these heavy trailers off-road puts a lot of strain on the mechanical components of the vehicle and especially the cooling systems. At the lower speeds encountered off-road there is less airflow over the radiators and oil coolers, resulting in potential overheating of the engine and gearbox.
To summarise then, as a guideline, the off-road trailer mass should not exceed about ¼ to ⅓ of the D/T of the tow vehicle if you are going to do any real off-roading.
Another aspect where the mass of the trailer is a huge problem is climbing slopes. Due to the fact that the trailer is dead weight, the vehicle / trailer combination will only be capable of ascending milder slopes. In addition, the surface of the slope plays a greater role. If the tow vehicle loses traction on a slope due to mud, the added mass of the trailer may be such that the brakes may not even be able to halt the descent. So, when inspecting the obstacle, take into consideration that should something go wrong, you may have to reverse back down the slope with the trailer attached.
The greatest problem one has is thus judging the capability of the vehicle / trailer combination. No text book can assist you with this, as there are just too many variables. The worst thing about it is that even the “experts” get caught out sometimes. The secret is, do not attempt an obstacle if you have not walked it, and even then take baby steps!
Tip: One thing you will need to learn and learn well is reversing with a trailer. If you cannot master this, do not even consider buying a trailer, as every off-road trip will be a nightmare.
The first thing one will notice is that the vehicle will be slower pulling away with the extra mass behind. Off-road this will become even more pronounced as the rolling resistance of the trailer increases in areas of poor flotation. But this is the easy part, it is stopping with a trailer that is hugely affected.
In the SA Licensing system, two distinct categories of “light” trailers are found. The first trailer, with an all-up mass of less than 750Kg, are not required to have a braking system. Trailers over that mass, are required by law to have a braking system that is automatically activated by the braking action of the tow vehicle. This is called an over-run brake or run-in brake. To see if your trailer is fitted with one of these units, firstly take a look at the axle. If there are rods or cables running from the drawbar to the axle, your trailer is probably fitted with a braking system. Then look at the tow hitch. A trailer with an over-run hitch is easily distinguishable as the tow hitch is mounted on a shaft, which can be “pushed” in (towards the trailer) thus applying force on the cable or rod system, and applying the trailer brakes.
One other system is found on very large trailers, which uses a system of air or vacuum to apply the brakes as soon as the vehicle’s brake pedal is pressed. However, this is seldom fitted to the trailers that are used off-road, so can be ignored for the purpose of this book.
A braking system most times includes a hand brake which allows the trailer to be stored without rolling away.
When reversing with an over-run fitted trailer, one must realise that reversing can apply the brakes in the same way as braking would activate them. To prevent this, the over-run hitch system is normally fitted with a locking device which often must be activated by a second person, standing next to the hitch as you start reversing. Once the lock has engaged, you will be able to reverse the trailer. However, some of these systems will disengage the locking device if the trailer runs faster that the tow vehicle for a few seconds, and then it will have to be reactivated before continuing to reverse the trailer.
Some trailers are fitted with an automatic locking system, which disengages the brakes if the wheels rotate in reverse.
Tip: Warning, this system works very well when reversing, but it may disengage the trailer’s handbrake when pushing the trailer backwards by hand.
When purchasing a trailer, speak to your dealer and make sure which system is fitted to your trailer. Make sure you understand exactly how to use it and what its limitations are.
But, while on the point of braking systems, it is highly recommended that any off-road trailer irrespective of size, be fitted with at least an over-run braking system. This makes the trailer much easier to manage on those steep, solid, dry slopes as the trailer will automatically brake thus assisting the braking effort of the tow vehicle. Descending steep muddy slopes with a trailer can result in the trailer swinging to one side and jack-knifing against the vehicle. If the wheels lock up in mud, the trailer still becomes largely uncontrollable. These situations should be avoided at all costs.
Most of the off-road trailers are now being fitted with the round LED “truck-lite” type lights. These are far superior to the older style lunch box shaped lights. Not only are they brighter and more visible, but they are much more reliable, especially those that are sealed units. But, the lights are only as effective as the wiring servicing them. Check that the wires are fitted within the chassis, well protected from flying stones and groping branches and bushes. Where they are exposed, such as where they couple to the towing vehicle, they must have additional sheathing to protect them from sand and stone damage. Make sure that the wires are long enough to allow the vehicle to turn without putting strain on them, but they must not be too long as they will drag on the ground when you go over obstacles. If possible, make a small hook out of a short piece of wire that will lift them up to the height of the tow hitch.
Keep the light sockets in a good condition and stow them well out of the way when the trailer is not in use, so that the jockey wheel does not run over them, and they do not get rusty.
One of the most common problems with trailer lights, occurs when the earth wire either on the tow vehicle’s socket or on the trailer is damaged, or badly connected. This manifests itself in the following way. Couple the trailer and insert the light coupler properly into the female socket on the tow vehicle. Now, with the ignition switched on, switch on the park or headlights, and one of the flashers. Now inspect the trailer lights. If the tail lights are on and only the indicator light is flashing, you are probably ok, just get someone to assist you checking all the lights and don’t forget to check the number plate light. However, if several or all of the trailer lights seem to flash randomly in time to the car’s indicator lights, there is 99% of the times, a bad earth. Start checking tracing this by checking the earth wire on the tow vehicle as it is most times the culprit.
Tip: Always carry one or two spare globes / lamps for the trailer (ask your dealer to include them in the cost of the trailer, they are normally very cheap) as repairing them when they are damaged can avoid a heavy fine.
All trailers must be fitted with reflectors. The minimum number is two white reflectors facing the front, two red ones facing the rear and three yellow ones per side, six yellow ones in all. Keep one or two spares as they are often destroyed by stones. In addition, a trailer must either have a chevron plate at the rear, or two large red reflectors, or a minimum of seven red reflectors in a specific pattern.
In South Africa all trailers must have yellow reflective tape applied to the sides and rear of the trailer, but all countries have different requirements. For example, in Mozambique a yellow diamond on a blue background (of a specific size) must be fixed on the rear of the trailer, and also on the front of the tow vehicle. The recommendation is that before towing in neighbouring countries, check which specific regulations are applicable with an organisation like the AA.
Jockey wheels, fitted to the nose of the trailer, must be equipped with a winding mechanism so that they can be used to raise or lower the tow hitch onto the ball of the tow vehicle, and to level the trailer when camping. They must be solidly constructed as, if the trailer is stuck in sand, they may have to withstand being dragged through the sand, under the full weight of the front of the trailer.
A jockey wheel should be able to retract until it is at least level with the bottom of the chassis of the trailer (it may not protrude below the chassis), or alternately be completely removable with a place to stow it out of harm’s way.
Just as a vehicle should be fitted with appropriate recovery points, front and rear, so a trailer should also be fitted with a strong tow eye front and rear, mounted to the chassis.
The trailer should also have jacking points which will take the high lift jack for hoisting and recovery.
Tip: When trying to move the trailer in deep sand, one technique that can be used, is to retract the jockey wheel to it’s lowest position, then slide a shovel under the wheel. This will give the jockey wheel a larger surface to press on and thus it will slide over the sand. The trailer can then be dragged through the sand using a tow strap, with the front resting on the spade.
· Learn to reverse with the trailer attached, using only side mirrors
· Purchase your trailer considering the capabilities of the tow vehicle
· Match the tyres, rims and track (axle width) of the trailer to that of the tow vehicle
· Make sure the trailer (when over 750 Kg loaded mass) is equipped with over-run brakes and teach your co-driver how to engage the reverse lock if fitted
· Make sure the electrical cables are well protected and clear of the ground or snags
· Keep in mind that the acceleration is impeded by the mass of the trailer, as is braking, so leave more space for stopping and increase following distances
· Trailers typically have a high centre of gravity, so take that into consideration when swerving to avoid potholes and crossing steep side slopes
· Plan you route carefully, take wider turns, allowing more space for the inner trailer wheel to turn, and avoid very narrow places
· Make provision for the extra mass, by avoiding steep inclines and descents
· Keep the speed down off and on-road
· Never overload the trailer and balance the load carefully, front to back and left to right.
· Load heavy items, lowest in trailer
· Remember that water and fuel is consumed during the trip, changing the balance of the load
· Take a spare spring or spring main blade along, as even if you do not have the skills to fit it, someone else in the group may be able to fit it for you in an emergency
· When trying to manoeuvre a trailer in thick sand using a tow strap, lower the nose onto a shovel so that it can slide along as the jockey wheel will just dig into the sand.