I used to work for a car company in Europe, and the towing standard that we worked to was, IIRC, ability to start and maintain towing on a 12 percent slope. That resulted in the maximum towing weight in the European car handbook.

I was also given to understand that in the USA there are longer and higher mountains that may need to be climbed (this was in relation to breathing, carburetion, etc.) which led to different general requirements, and I could well understand that it might also lead to different criteria for towing. You also commonly have more extreme temperatures than we normally operate in..

It is common in Europe to tow 15m glider trailers with relatively small cars – in the 1970s, I used to tow with 1100cc small family cars. I only got stuck once on a 1 in 4 (25 percent) hill, when I could not take a run at it. Most people these days can run larger cars, but still much smaller engines than are common in the USA. FWIW, I always have auto these days, with a 2.0 litre engine, and that is fine for our conditions in the UK.

Somebody with more up to date car company exoerience may be able to throw a bit more light on it.

I did find mention of a proposed USA (SAE) standard which includes a 12 percent slope. See:

http://www.trucktrend.com/features/c...y/viewall.html



Chris N