Gilbertd wrote:
Yes, I suspect that the fact that both axles are driven on our cars is the reason why they are plated to tow a greater weight than the car. As far as trailers go, it's the MAM, or Gross Vehicle Weight as it used to be called, that is relevant. So even a little box trailer that may weight about 100 kgs when empty, will have a MAM of up to 750 kgs so doesn't need to be braked (and can be towed by these youngsters). It also means that every trailer must now go through an IVA test so it can be plated and certified to show it's MAM. Technically, gone are the days when you could just weld together a few bits of angle iron, stick a pair of wheels and a tow hitch on it and use it (even though lots of people still do).
There was a big fuss a few years ago within the motorhome fraternity who are in the habit of towing a small car behind their mobile 3 bed detached. Even though quite a few smaller cars weigh less than 750 kgs unladen, it's that MAM that is important and with all other than the Smart car, their maximum loaded design weight is over 750 kgs. The law states that a trailer with a MAM of over 750 kgs must have brakes on all wheels so a simple A frame isn't good enough, they have to have a mechanism that applies the brakes on the car being towed. That also means that a braked two wheel dolly that lifts two of the towed cars wheels off the ground still isn't good enough as the other two wheels aren't braked.
The rules are completely different for recovery as opposed to transport, where a dolly or spectacle lift are good enough. The emphasis being on getting the dead or damaged car off the road as quickly as possible. So when you see one of these transporters loaded with scrap cars off to the crusher with an extra one on a spec lift on the back, that is actually illegal as the car on the spec lift is being transported rather than recovered.
Yes - I've seen ways of applying the vehicles own brakes in this situation, but at best they appear to be a bit of a bodge job (some sort of mechanism to push the brake pedal down by something else wedged against the drivers seat, looped in through the window, the better ones appear to use a method of hooking to a modification to operate the brake via a cable through the engine bay. Neither would have any vacuum assist though, which could be argued as not having fully working brakes etc).
It seemed to me having looked at it that the best bet was if you wanted to drag a car around behind you either get someone else to drive it, or use a trailer (in either case adding the advantage of not having to have a Smart car!)