Morgans wrote:
"Robin" wrote

I want to replace the tires on my Komet trailer. The original tire
size is P165/80 R13, which is now hard to find.

I plan to tow about 75 mph most of the time. I really want to avoid
sway.

Yes, add another axle behind the one there, then use any tire you want, and
it will never sway again.
Not true.

Double axle trailers do sway, and are in general more unwieldy than
single axle trailers. A poorly designed trailer will sway at lower
speed, adding an axle seems to increase the speed at which it goes wrong
at the expense of making the transition from stable to out of control
much sharper.

If you want demonstration try towing just about any poorly designed twin
axle trailer fast enough that you get vortex shedding. A light crosswind
is "ideal" for making this exciting.

Use a tyre rated for the job at hand. Stiffer sidewalls help. Lower
profiles help at the expense of being rougher on the glider. Correct
inflation helps.

Learn what a tyre is designed for by reading the sidewall - to
understand the sidewall code look at -

http://www.etyres.co.uk/consumer-inf...ewall-code.htm

Radials are generally better than crossplies which are generally limited
to "cheap and nasty" applications around here. If you want a durable
trailer tyre for your tractor trailer they make a good choice. At speed
on the highway I would be/am much happier with a tyre rated for the
speed, and with similar compound to the towing vehicle. That means you
should look at the traction grade indication too. It would be
embarassing to have your trailer break traction on a fast sweeping turn
that is not even making your tow vehicles tyre work...

For what it is worth - I have two trailers.

15m std class - streamlined enclosed trailer.
Single axle running on LT. (couple of extra plies in the sidewall)
LT175/70R13S
So a less compliant casing radial, with speed rating of 116. Tows stable
at 120km/h and is reasonably good at not transmitting shocks to the
trailer.

The 19m Kestrel is in a poorly streamlined twin axle trailer.
Both axles have P175/70R13R tyres.
This is unstable at any speed above 100km/h, pushes the tow vehicle
around and is generally unpleasant. Too much compliance in the sidewalls
lets the tyre develop big slip angles which then try to steer the tow
car. In tight turns one of the axles has to scrub, grabbing and releasing.
This winter's project is to convert it to a decent single axle...

Of course the bottom line is to drive a little slower - as well as
having the right tyres on the trailer.

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