[TR] Trailer Physics

[John Macartney]

I've been watching this thread with interest as when I'm not fiddling about with Triumphs, writing 
or talking about them - my wife and I like to spend as much time as we can in our trailer home 
somewhere in the UK. Mostly we do this at weekends. To input further comment on this thread, its a 
widely accepted practise in the UK and Europe that for safe towing - whether a caravan (trailer 
home) or a simple trailer, the following facts are observed:

1. A four wheeled trailer is better than a two wheeled trailer. The two extra wheels give valuable 
extra stability, especially in cross winds.
2. The all-up weight of whatever is on the towbar should not be more than 80% of the towing vehicle 
weight. A 90% weight is about the maximum. The police tend to take a strong interest in any heavy 
load that looks heavier than the tow vehicle.
3. If the towed load exceeds 350lbs total weight (including trailer weight) the trailer must have 
its own braking system. Usually this is a mechanical set-up activated by the telescoping action of 
the towhitch on the vehicle towball.
4. Trailer noseweight (the downward thrust on the car towball) should be between 70-100 kgs 
(140-200lbs approx). You can easily calculate this by placing a set of bathroom scales under the 
trailer tow hitch and supporting it with a piece of 3"x3" timber.
5. The load in the caravan or on the trailer should be placed ideally over the trailer axles and 
slightly nose heavy and calculated as in 4 above.
6. Speed is restricted to a maximum of 60mph.
7. Trailer tyres should never be the same as car tyres. You need considerable extra strength in the 
side walls. Mine are 8 ply steel and I change them every five years.

I have two trailer homes and a small household trailer, all of which are used regularly. While I 
always carefully check total trailer weight, load position and towball downthrust, all my trailers 
are fitted with an additional anti-snaking device that I can transfer from one unit to another. Even 
with a properly loaded trailer or caravan, snaking is often encountered by the suction effect of 
passing trucks and buses and my Bulldog set-up stops it even starting. Happily, all larger trailers 
and all caravans are now fitted as standard with an anti-snake lock when delivered from the factory.

FWIW....

Jonmac