Don.
You need to update your driving knowledge - the UK speed limits for towing
a trailer is 60mph

https://www.gov.uk/speed-limits

At 17:13 05 October 2016, Don Johnstone wrote:
At 14:59 05 October 2016, Charlie M. UH & 002 owner/pilot wrote:
I've wondered if adding a small (1/4" - 3/8") anti sway bar to th
trailer
axle would help in most situations. Granted, proper weight is best, bu
the
anti sway bar may widen the margin.
Thoughts?

Weighting is important, no doubt. Reducing the weight and therefore th
inertia on the anchored end of the trailer does reduce the possibility o
any swing increasing by increasing the ability of the towing vehicle t
damp the oscillations. The trigger for these oscillations is aerodynami
caused by the low pressure area between two vehicles as they overtake/ar
overtaken. The situation is made worse if the vertical surface is the sam
or more than the area in front of the axle. Cobras and Komets are designe
to reduce the side area behind the axle.
I towed a trailer, containing a Grob 103 back from Holland. The nose
weigh
was close to the maximum limit allowed for my car, theoretically the bes
situation to improve stability, however it swayed readily. I have jus
towed the same combination over 300miles. Before leaving I increased th
tyre pressures on the trailer from 35psi to 55psi (Max 65psi). The traile
now tows with no swaying up to the maximum speed limit in the UK (70mph)
It does allow towing at just below 60mph which means I can avoid bein
overtaken by large trucks, the condition which is most likely to trigge
swaying. Tyre pressure appears to have a large influence on the stabilit
of the trailer, greater than loading. Vertical instability is now the
majo
problem, easily fixed by a stabiliser.