Choosing a towcar for your caravan - weights and measures
However, there’s a bit more to it than that…the heavier the car, the higher its potential tow weight – albeit within the design constraints set by the manufacturer (for example, sometimes the gearbox can’t cope with the extra strain of towing).
Take the Land Rover Discovery TDV6: it tips the scales at a hefty 3240kg and can tow up to 3500kg.
Choosing a towcar: Squat down fatty!Think of a Sumo wrestler: a solid chunk of muscle and fat. If he stands up, he’s quite top heavy and offers less resistance to a hefty shove. As soon as he squats down, though (thereby lowering his centre of gravity) it’s a very different scenario: he’ll be able to resist incredible forces and remain far more stable. Good luck with trying to push him over.
It’s a similar principle with towcars, and the key to a successful tow vehicle is one that has a low centre of gravity combined with a reasonable amount of bulk.
However, good as a heavy, low slung coupé would be towing on the flat, you do need a certain amount of ground clearance to cope with grassed pitches and the more basic campsites.
Choosing a towcar: WheelbaseWheelbase is the distance between the centre of the front wheels and the centre of the back wheels. Limos excepted, the general rule of thumb is that vehicles with longer wheelbases are inherently more stable and better suited to towing.
For an extreme (and very funny) example of this theory at work in the real world type in ‘Renault 5 and caravan’ at www.youtube.com and see why small cars and twin axle caravans don’t work…
Long wheelbase cars tend to be less ‘twitchy’ when towing, and the only downside to having a longer wheelbase vehicle will be the possibility of a wider turning circle – although the maximum angle of the steering also has something of an influence on this.
Choosing a towcar: TrackWhile a longer wheelbase can offer stability benefits, so can a wider track. The track is the distance between two wheels on the same axle. Think of our Sumo wrestler again – if he stands upright with his feet together (a narrow track) he’s easier to push over than if he has his feet planted a metre apart (a wide track).
So with a vehicle, a wider rear track will improve stability. Many cars also have a wider rear track than the front as this gives handling benefits. As with wheelbase, a longer rear track will increase the likelihood of the car being a handy tow vehicle.
Choosing a towcar: Rear overhangShort rear overhangs behind the back wheels have a number of advantages. Long caravans with single axles can be prone to wagging the car, especially in a crosswind, and the further the actual tow hitch ball from the centreline of the rear axle, the more pronounced the effect that will be felt in the car.
In theory, if you could have an extremely heavy vehicle with the ball hitch inline with the rear axle centreline, the effects of the caravan wagging would barely be felt in the tow vehicle.
In practice, the tow hitch has to be further back from the axle for packaging and practical constraints. Four-wheel-drives with spare wheels mounted on the rear doors often have to have longer towbars, for example.
Choosing a towcar: VerdictThink fat, wide, long and with a short rear overhang when considering your next tow vehicle, and you’ll not go far wrong!
- This article is taken from the May 2010 issue of Go Caravan magazine.