Rick wrote:
1 - 2 tonnes a cubic meter for rubble, and unbraked you have to be
less than 1/3 of the weight of the towing car.

Not true I don't think, see:-
http://www.dft.gov.uk/stellent/group...ds_506866.hcsp

The limit for an unbraked trailer behind a private car is simply 750kg
and that's it.

No, sorry, there *is* a limit on the relative weight of an unbraked
trailer even though there isn't a general limit. I quote from the
above:-
"In use it is not permitted to use an unbraked trailer the laden
weight of which exceeds 50% of the kerbside weight of the towing
vehicle."

Sorry, I was out with my actual figure, but the point remains true, as
most cars don't weight that much, an unbraked trailer can only take a
small volume of rubble.

We run two Citroen XMs, both have towbars. If I remember right their
kerb weight is something like 1400kg so we'd be able to take an unbraked
trailer up to nearly its maximum weight. I know the XM is a big car but
modern cars are actually rather heavier than older ones, partly because
we all drive bigger cars than we used to.

There are not so many unbraked trailers that are rated for 750kg
anyway, the typical 'small trailer' seems to be in the 300kg to 500kg
range.

--
Chris Green