wrote:
Ken Ward wrote:
what's the story on tires? is it OK to use regular automotive radial
tires or are ST tires required?

Ken, what trailer do you have, what tires are on it now, and is the
towing stability satisfacory?

Almost no trailer loads a tire as much as a car.

This might lead the unwary to think they can get by with a lesser tire
than they could on their car, yet glider trailers seem to suffer far
more tread separations than cars do (mile for mile). You need to match
the tire to the load, and trailer tires are rated differently than car
tires. Generally, passenger car tires need to be derated about 10% from
their load rating to be equivalent to a trailer tire rating.

That said- a couple things to consider-
A slightly lower profile tire can go a long way toward reducing
sidewall flex which does feed back to the towing vehicle as sway. Paul
Cordell found some cool inexpensive wheels for his Cobra trailer that
were larger in diameter allowing low profile tires and retaining ride
height.

It's not sidewall flex that's the important factor, but "lateral slip
stiffness", but enough of the technobabble - it's not something you can
read on the tire spec sheet in any case. Lower profiles tend to have
this, as do higher speed ratings. So, if stability was an issue, going
to a lower profile and higher speed rating will help. Lower profile
tires tend to ride harder, and may be more susceptible to impact damage
from potholes, road hazards, and things like curbs, so they should be
checked more often.

Speaking of speed, ST tires are rated for 65 mph, unless you run them at
a much higher pressure than the load rating tables show. Be careful if
you plan to tow at 65+ with an ST rated tire. For towing above 65, I'd
use a high speed rated tire instead of an ST tire, and (somewhat
arbitrarily) pick one rated for at least 20 mph higher than I intended
to tow.

MOST IMPORTANT- A not well know fact is that materials of tire
construction have changed and the usefull safe life is less due to
aging affects. Car manufacturers now specify replacement after 5 years.
This is mostly due to changes made to get long wear life and better
fuel economy.
The bottom line is it probably less important what you change to than
that you change.

Indeed.


--
Note: email address new as of 9/4/2006
Change "netto" to "net" to email me directly

Eric Greenwell - Washington State, USA

"Transponders in Sailplanes" on the Soaring Safety Foundation website
www.soaringsafety.org/prevention/articles.html

"A Guide to Self-launching Sailplane Operation" at www.motorglider.org