My observation on trailers is not based on what is the legal limit i can get away with but on the facts of use. The recent auction now suggests that it is easy for a Microcar owner to put a car on his trailer worth some £20,000 and a rarity could approach £50,000.
For me I want a trailer over-engineered for the task so;
I pick a twin axle. This way I can afford a puncture with minimal chance of a lose of control.
I pick a trailer with brakes so that if the trailer should part company it will attempt to stop itself when the handbrake safety cable deploys. A four wheeled trailer is both more predictable and balanced if loaded correctly so less likely to crash.
I pick a trailer that is finitely larger in all dimensions than the cars to be put on it so there is minimal suspension issue if there should be a failure or overhanging car to be damaged by road flak.
That sounds expensive, you might say. Not really as there are quite a few racing car trailers about that are prefect for the task but yet run to about £400 as they cannot really take anything heavier than a tonne nor longer than 12 feet, comfortably. They are normally relatively light weight so cheaper to tow than a full car trailer.
I then match that to a suitable tow vehicle that can boss the trailer about. Larger the trailer the larger the tow vehicle. My trailer tows perfectly behind a Citroen BX, which is a lightweight in modern car terms, of just under a ton (before you say it, with anything over 3/5 load it goes behind the Van).
I also make certain my insurer offers good coverage for trailing rather than take a chance of not reading the policy agreement which normally will not include a trailer or load unconnected to the car. A key phrase that has seen many lost trailers/poorly tied cars not covered during and after calamity, even if the fault was someone else's. Indeed such are the risks of trailing it is one reason I own a van! It is a safer transportation method to have the vehicle inside.
As an old trailer mine has no modern maximum weight stated, cannot remember when all that was reviewed now. It has got a proper towing assembly on the front of the A frame and that has its own allowable towing weight, which I believe is 3.5 tonne. Any pedant would look extremely foolish attempting to apply the rules to that parameter on the rest of the trailer, as it clearly would collapse under the strain. I suspect this trailer would be fundamentally illegal outside Britain because of this lack of ID tag and specification. Certainly the Germans have been ahead of the rest in insisting trailers be subject to firm construction criteria with laws and testing to back it up. The Peka, 1959, carries both the trailer makers plate and the constructors plate marking the specification within the makers specified parameters to class the caravan at 240kg and a loading of 400kg on tow. The info missing on my car transporter, effectively.
Statistically more cars get damaged on trailers than do being driven on the road.
So other than the pedant level I feel I can take the risk of putting a Messerschmitt, Brutsch or such on my trailer. If a Tiger I might think about getting someone in as £90,000 odd dangling behind my car is too much of a risk for me. For the same reason I have to chuckle at the welded bedsteads with wheels passing as trailers that appear behind £25,000 plus campervans loaded with £15,000 worth of car at microcar rallies. The very reason the BUMS started the ironic best trailer at the show award, which later got taken up as a serious prize at certain events!
On the other side of course is the size of garden in which to store the trailer, the size of the available tow car and what is being towed to where and how often. I probably do more towing than most people even now so my solution is a definite requirement for me against the risk over time.
Just in case you think I have become far to sensible in my old age I would point out that recently I was seen towing a Mercedes Benz 190 Fintail on Dave's indestructible transporter behind the old BX. So about 21/2 ton behind a ton of car, just like the old days. The BX coped wonderfully since it has fantastic LHM brakes, suspension, steering. No other car of that size would cope with what was a 4wd load, really. Very naughty but it makes you feel young again.
