David MottonSee other Blog articles filed in ‘Tow cars’ written by David Motton
Tow Car Editor
Few topics in caravanning create more debate than the 85% rule. For years, many tow car drivers have lived by the advice that a caravan should weigh no more than 85% of the kerbweight of the tow car. Some disagree and think the rule is nonsense. Others believe it's time to look again at whether 85% is the right ratio.
The first thing to remember is that the 85% 'rule' isn't a rule at all. It's a guideline. More than that, the 85% figure is particularly aimed at inexperienced drivers.
The Caravan Towing Guide is produced by the National Caravan Council, and supported by both The Caravan Club and The Camping and Caravanning Club. It gives advice on all aspects of towing, including the weight ratio of car to caravan. It states that: "For a novice caravanner, ideally, this ratio should not exceed 85%. For an experienced caravanner the maximum recommended ratio is 100%, provided the figure is permissible in respect of the tow car’s published capability."
You can argue about when a novice becomes experienced, but it's clear from this that the NCC and both major clubs see towing up to 100% of the car's kerbweight as a perfectly reasonable thing to do once you've been towing for a while.
So, if you've been caravanning for years and have always treated 85% as your maximum matching ratio, don't be put off towing a heavier tourer.
The trouble is, whether you are a novice or an experienced tow car driver, new cars keep on getting lighter. Almost every new model weighs less than the one it replaces, and sometimes the difference can be hundreds of kilos. That's good news for improved economy and lower emissions, but it doesn't help with matching ratios – watch our video for more about outfit matching.
At the same time, technology in both the motoring and caravanning worlds is making towing safer and more stable than ever before. Stability control on new cars is now ubiquitous, and research by Bailey, The Caravan Club and the University of Bath has shown it to be effective in dealing with instability while towing. That research was published in 2007, since when many new cars have been fitted with a Trailer Stability Programme (sometimes called Trailer Stability Assist or Trailer Sway Control), which recognises when a car is towing and effectively puts the stability control system on high alert. These systems are very effective in dealing with a snake, when side-to-side movement from the caravan is passed on to the car and threatens to cause an accident.
Most modern caravans have stabiliser hitches, and some vans also have stability systems such as Al-Ko ATC or BPW's iDC system. These apply the caravan's brakes if sensors detect any snaking. Shock absorbers have also become more common in recent years, improving stability especially on poorly surfaced roads.
So, if cars and caravans have become safer and more stable since the 85% and 100% matching figures were set, is it not sensible to revise these figures upwards?
I'm in two minds. Part of me thinks that if we are now towing more stable outfits than, say, 15 years ago, why give away that improvement? All other things being equal, the more favourable the matching ratio the more stable the outfit will be.
I also worry that there's too much emphasis on the matching ratio and not enough on other aspects of safe towing. A van loaded to 70% of the car's kerbweight could be unstable if it's poorly loaded or has incorrectly inflated tyres. Whatever the matching ratio, it's important to keep heavy items low down and close to the caravan's axle and to make sure every aspect of the tourer is in roadworthy condition – watch our video to find out more.
On the other hand, the trend for lighter cars isn't going to go away. So it's sensible to take another look at matching ratios, but to do it in a rigorous and scientific way before making any decision.
It may not be perfect, but the 85% guideline has served a useful purpose for many years. If the time is right to make a change, let's be sure of our ground first.
And for additional advice on towing, outfit matching, hitching up and more, check out our towing masterclass videos.