Doctor Diesel

Weighty Question

Dear Doctor


Re: Modern vehicles and their specified towing weights: Would you please explain the relationship between vehicle kerb weight and trailer gross weight? It would seem the Caravan Club’s advice of 85 per cent for trailer weight against towing vehicle weight is no longer valid in the modern vehicle manufacturers’ world. Your data for the current Skoda Octavia, for instance, shows the top specification 4×4 model with a kerb weight of 1,500kg for the car and a maximum trailer weight of 2,000kg. Surely this might be a recipe for “the tail wagging the dog?” 



Harry Ayling


Hello Harry


Thanks for your message. I have today consulted the Diesel Car towing expert, our Editor Ian Robertson, to confirm my own thoughts, and he has advised me as follows: He recalls that, some years ago, a Daimler (Mercedes-Benz) engineer told him that the high torque figures of diesel engined towing vehicles allowed them to safely, and comfortably, tow caravans and trailers that exceed the weight of the towing vehicle involved. Evidently the manufacturers perform a series of test runs, involving things like pulling away on a specific gradient, to arrive at their maximum towing weight figures. From existing knowledge, I imagine that they would know pretty well what sort of figures to expect, even before such tests, based on the engine performance and the traction abilities of the drivetrain and wheel/tyre combination. 


With a 4×4 car like your Octavia, the superior traction would aid progress considerably in this kind of test, and this explains the higher 2,000kg rating compared with the 1,600kg for the 2WD 2.0 TDI variants. Ian feels that the Caravan Club is possibly not in touch with all of today’s cars, and the benefits of their electronic traction aids. The 85 per cent rule was set back in days when cars were less advanced, but they have stuck to the old rules. Apparently, the Caravan Club do add a caveat that “experienced” towers can go up to 100 per cent of the towing vehicle’s kerb weight, although this would still be well short of the 2,000kg Skoda rating. In a world of frequent litigation, one feels that manufacturers would not issue their figures if they were not confident of being able to back them up in court, were it to come to that. I might also add that today’s braking systems are also far superior to those of past times! I hope that you find this a satisfactory answer to your enquiry! 


Best regards, 

Doc Diesel

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