What do you think of the 85% rule?

[Parksy]

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It is a pity more manufactures don't quote a more realistic maximum towing weight limit for a particular model.

Hello Gaffer,

Can you define what a more realistic towing weight actually is?
How would you derive your chosen value? Would it apply to all trailers, or just caravans or indeed all sizes of caravans?
What would be the measure of success or failure?

The maximum towed weight limit for any vehicle is not contrived by a committee, or someone holding a finger in the air, but as the result of a set of repeatable tests. (notwithstanding the VW emissions debacle).

There would be no reason for a car manufacturer to artificially reduce a towed weight limit, as that would reduce its appeal to the widest possible market.

Perhaps the caravan Industry would like to take a leaf out of the car industries book and actually tell us how they came up with the 85% guidance figure - It seems the origin of the guidance is as anonymous as you and I.

There appears to be less emphasis on the 85% recommendation than was perhaps once the case according to the C&CC car and caravan matching guide.
From what I've read over the years no authoritative source has ever suggested that the 85% figure would provide any guarantee of towing safety or stability.
The 85% figure was just one of a set of recommendations arrived at by authoritative sources within the caravan and automotive industries to provide a sensible baseline for those who are new to towing a touring caravan.
The best way to look at it would be to recognise that if a newbie caravan owner adopted the 85% guideline there wouldn't be the tendency to overload a touring caravan that we see all too often on camp sites.
I'll stick my neck out and state that if a tourer owner used the 85% guideline along with the other safety recommendations provided by authoritative sources there would be a better than evens chance of the owner keeping their pride and joy shiny side up when towing, and less likelihood of them 'starring' in a radio traffic bulletin about their caravan and its contents spread across three lanes of a motorway.
There has never been any suggestion that the 85% figure is the sole criteria for towing safety, it is a minor component of the sum of advice provided by authoritative sources such as the CC, the C&CC and motoring organisations based at least in part on years of experience and engineering data.

 

[Gafferbill]

.......a more realistic towing weight for a particular model of car should represent a weight figure that that particular model can safely legally tow.

The legal standard is set at the moment solely by a test of performance in a straight line up an incline.
IMO this test is not comprehensive enough and leads to confusion, but is not likely to be improved by manufactures as it flatters their vehicles.
I would suggest that the 85% towing ratio guidance has come about from experience over a period of time by a lot of drivers that tow.
Collectively they have decided that manufactures figures are mostly unrealistic.
Why that particular figure?
You could ask why is the speed limit 30mph in built up areas.........yes that has legal backing but only after that figure was derived at after a consensus of opinion.
The law has decided that 30mph is safer than 35mph......probably very difficult to prove and like towing ratios only one of a host of safety factors involved.

I have always said once the towing ratio is decided when the outfit is matched a whole lot of equally important safety related criteria have to be adhered to.