Date:24 August 2011
Don’t confuse towing a caravan with driving a car – they only look the same. By Mike Allen
The caravan is doing a lazy samba behind your SUV as you drive down the highway, swaying side to side far enough to intrude into the neighbouring lanes and tug at your vehicle’s rear end. It feels spooky and is, in fact, unsafe. Funny, the thing was as stable as a mountain goat on a hillside when you left this morning. Since then, the only changes you made were to fill the water tank and to load the rear with camping gear and luggage.
Towing can be a trial. Seemingly minor details – such as adding weight to the rear – can make profound changes in the rig’s stability. But, by following a few simple guidelines, you can stay on track, towing with the utmost ease and safety.
The right gear
All hitches are not created equal. The weight that your vehicle can tow is specified by the manufacturer and listed in the owner’s manual. My advice is to install a towbar that’s heavy-duty enough to match your vehicle’s GTW and nose-weight spec, even if you’re planning on towing only a small trailer. Don’t forget to factor in the weight of the trailer’s contents – including the capacity of the fresh-, grey- and blackwater tanks – when you’re shopping around.
Setting the hitch height
It’s important that the loaded trailer or caravan be level with the ground when it’s attached to the vehicle, and that you trim the trailer’s flatness either with an adjustable towbar or by finding one with the right offset or drop plate adapter. (If you end up using an offset type, make sure it’s rated to handle the trailer weight.)
First, you need to find the height of the trailer’s nose when the trailer is level. Set up the trailer on a flat surface. Run the nose jack up and down or prop it up on some scrap timber until it’s level. You can determine this by placing a carpenter’s level on the nose or by eyeballing the trailer from the side from a distance of about 15 metres. Measure from the ground to the top of the ball socket.
Park the vehicle you’ll use to tow the trailer on level ground, too. Then measure from the ground to the top of the towbar receiver plate and add 75 mm to accommodate the height of the ball.
Typically, the ball is a good bit higher than the trailer nose, so the difference is the approximate amount the towbar will have to be lowered. I say approximate, because the weight of the trailer will compress the vehicle’s springs. Hook up everything (with the trailer loaded) and again measure the trailer’s attitude. You’ll likely have to adjust the towbar height again.
Sure, you know how much the trailer weighs, because it’s printed right there on the registration, right? Don’t believe it, as the listed weight probably doesn’t include a camper’s furniture or the cargo on a utility trailer. Accessories added at the dealership, such as an auxiliary battery, ramps, tie-down rails and whatnot, can make the gross weight climb substantially. The only real way to know is to weigh it, which you can do for a minimal fee at most scrapyards.
Before you head to the scales, load up all the items that you plan to haul, and fill the water and gas tanks. After you arrive, first get the overall trailer weight by disconnecting the trailer and resting the entire rig, wheels and nose jack on the scale. Next, find the nose weight by hitching up the trailer and leaving only its tyres on the scale. The difference between the two measurements is the nose weight. You want roughly 10 per cent of the trailer’s weight on the nose. Shift the cargo fore and aft until you get the correct weight distribution.
Note the position of the load (a camera phone comes in handy for this) so you know for next time. And if you’re changing cargo, but don’t have time to visit the scales, use our home-brew method (see “Set your nose weight”) to get an accurate measurement.
Don’t trust anything to stay put in or on a trailer once you’re under way. Clip or bungee cabinet doors and drawers. Use ratchet tie-downs to keep stuff in place.
Inflate the tyres to the caravan or trailer manufacturer’s maximum recommended cold pressure. Heat is the tyres’ enemy, and a properly inflated tyre will run cooler. Be even more careful of the small tyres on light-duty trailers – the tiny outside diameter means they spin faster. A high-speed run on a hot day with a ton of bricks on board could overheat the tyres or wheel bearings.
Whenever you hook up the trailer, check that all of the lights are working. You can do this without making four trips up to the cab and toggling on all the turn signals and brake lights in succession. Turn on the parking lamps and the hazard flashers. Walk to the back of the trailer. If the parking lamps and flashers are on, you’ve got turn signals and brake lights, because they’re the same filaments as the hazards. This assumes, of course, that the vehicle’s brake lights are working.
On the road
Regardless of how tightly you cranked the tie-downs on that car, bike or ATV, road vibration can loosen them. So, about 20 to 30 kilometres after you depart, stop and check their tension. After a few hours on the road – and every time you stop – inspect the trailer. Make sure the towbar and wiring are secure.
Next, kick the tyres to see if they’re properly inflated. Tyre pressure and properly functioning wheel bearings are crucial. Heat is the telltale sign: you just don’t want any tyre or wheel bearing to be significantly warmer than the others. I use an infrared thermometer – or my calibrated palm – to check the temperature of both. A tyre becomes hotter if it has less air pressure than the others, so check for a leak. A toasty wheel bearing is on the verge of failing. At the very least, pop off the bearing cap to see if there’s sufficient grease in the bearing cavity.
Every morning, check the tow vehicle and trailer tyre pressure, as well as the trailer lights and brakes. Ditto for any tie-downs. Don’t forget to shut off the gas at the tank, and the electric water pump at the breaker. If you’ve got an auxiliary battery, be sure it’s turned off and connected to the vehicle charging circuit so it’ll charge while you’re under way.
One last tip: if you’re towing to a campsite, leave the freshwater tank empty until you’re on-site. No sense in towing several hundred kilograms of water cross-country. Ditto for breaking camp: empty the black-, grey- and fresh-water tanks at the campsite instead of towing all that extra weight around.
One – Cross chains for safety
Chains serve as the hitch of last resort: if the nose ever loses its grip on the ball, the chains will keep the trailer from vaulting the guardrail into oncoming traffic or something equally inconvenient. Cross the chains under the nose – if it slips free, it’ll land on top of the crossed chains rather than hitting the road. A bonus of the X configuration: the chains won’t come up short in tight turns.
Two – Check the trailer wiring harness
This industry-standard plug and socket wiring and colour-coding scheme should make it easy to install the connector properly to the tow vehicle’s harness. Spray the contacts with dielectric grease to prevent corrosion.
Three – Always check the brake battery
Trailers with electric brakes rely on a small gel-cell battery to initiate stopping when the breakaway lanyard is pulled. Normally, the battery charges whenever the vehicle engine is running. But it’s smart to check it before hitting the road; faulty wiring or lengthy storage can sap the juice. Use a test light or voltmeter to make sure the battery is alive; if not, hook it up to an external charger to ensure the brakes are in working order.
Four – Set your nose weight
Swaying caravans and trailers are almost always the result of insuf cient nose weight, because adding weight here adds stability. If there is zero nose weight, the trailer’s centre of gravity (CG), the point around which it pitches, yaws and rolls, is centred between the tyres’ contact patches. This will provide no stability – speci cally in yaw, or sway. Adding weight, by moving cargo in the trailer forward, pulls the CG forward of the tyre contact patches. The drag of the tyres will tend to pull the CG back on to the centreline of the vehicle and trailer. The more nose weight, the farther forward the CG goes, and the more stability in sway, right up until you add too much weight for the tow vehicle’s rear suspension to handle. Industry-wide, the target recommendation for nose weight is 10 to 12 per cent of total trailer weight. Here’s how to check nose weight if your trailer weighs so much that your bathroom scale won’t read high enough. With the nose resting on the beam one-third of the distance between the pivot and the scale, a 64-kg reading means that the total nose weight is 190 kg, just about right for a 1,8-ton caravan.
Five – Set up an equaliser hitch
Once you’ve dialled in enough nose weight for stability (about 10 per cent of the trailer’s weight), there may be too much pressure on the towbar. Equalising bars (right) induce a rotational force around the hitch and pivot horizontally, transferring some of the nose weight to the vehicle’s front axle. The stiffness of the bars needs to be correct for your particular trailer, so consult the manual or a trailer specialist. I generally adjust them so that, when the equaliser bars are installed, the towbar rises back to within 25 mm of its un laden ride height.
Match bar to car
On the face of it, a towbar might appear to be a simple device. But, with the current generation of motor vehicles, the towbar needs to be integrated into the design from an early stage and should be thoroughly tested before the vehicle even reaches the market says Mark Gutridge, product development director of Thule Towing Systems South Africa.
A good indication of design quality is the ofcial approval of a towbar by an independent organisation such as the United Kingdom’s Vehicle Certication Agency. The VCA approval number can be found on the type plate of the towbar together with a listing of the load for which the towbar is rated..
A tested towbar uses vehicle-specic, homologated attachment points, Gutridge says. Poorly designed and mounted towbars can cause structural damage to a tow vehicle by feeding excessive loads into the vehicle’s chassis. Ironically, some of highest risks come not when towing, but when carrying bicycles on a towbar. Cross a speed hump fast, and you multiply – many times – the torque created by up to 50 kilograms hanging behind you.