Bruce Hoult wrote on 3/4/2018 8:35 AM:
Sidewall stiffness helps. Either inherent -- crossplys are better than radials, all else being equal -- or created by pumping them up to the maximum pressure.

Realistically, the only time you can choose crossply (aka "bias ply") tires is in
the "ST" category (trailer tires), because they aren't commonly available for
passenger cars. The steel belt gives the tire tread more lateral stiffness than a
the same size non-belted crossply tire, and consequently more stability to the
trailer. There are other very good reasons radials are the most common car and
trailer tire; the only advantage of a non-belted trailer tire is lower price.

I actually did the experiment last year, putting same size radials and bias ply
tires on my trailer. The radials let me tow about 7-10 mph faster. Contrary to
"common knowledge", the radial ST tire deflected less laterally than the same size
bias ply ST tire. A similar (not identical) size LT radial tire had even less
deflection than the other two when tire pressures were set for the same load rating.

It's a small sample of the tire universe, but illustrates choosing by assumed
sidewall stiffness is not a good way to choose tires.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/...anes-2014A.pdf