Sipes / The A/T
III features a lim-
ited number of
sipes, positioned
to produce trac-
tion in wet/winter
conditions by
increasing the
number of bit-
ing edges in the
tread while pulling
water away from
the road surface.
Shoulder
Design / The
staggered shoul-
der blocks on theA/T III present
additional surface
area to promote
better traction in
soft terrain.Tread Pat-
tern/ The tread
features circum-
ferential grooves,
which evacuate
water, and lateral
grooves, which
optimize trac-
tion in snow, dirt,
and mud. Toyo
has also designed
the tread blockarrangement and
rigidity to provide
improved steering
feel and handling.
Rubber
Compound / A
high concentra-
tion of silica in the
rubber compound
allows the tire to
remain flexible
in cold tempera-
tures—optimizing
wet and winter
traction while
preserving tread
life.turers to design their tires to preserve all-terrain
performance while eking out more winter usabil-
ity. On the surface it sounds like an easy job, but
cold-weather convenience comes at the detriment
of year-round performance and tread life, which
is what engineers need to balance when gunning
for 3PMSF.
Before we get into the specifics, some
background. In helping drivers gauge the snow-
worthiness of a tire, the U.S. Tire Manufacturers
Association and the Rubber Association of Canada
agreed in 1999 to a performance-based traction
rating for truck and car tires. Denoted with a Three-
Peak Mountain Snowf lake symbol (which appears
on the tire sidewall as a snowf lake inside a moun-
tain), the designation requires that tires pass a series
of tests in snow. This is measured through an accel-
eration test through hard-packed snow designed by
the American Society for Testing Materials.
Ahead of the test, the tires are cooled down to
match the air temperature. During the evalua-
tion, the road surface must have at least .75 inch of
medium-packed snow on top of 1.2 inches of hard-
packed snow—with ambient temperatures around
5 to 25 degrees Fahrenheit. The test will then mea-
sure the distance it takes the vehicle to reach 6 mph
and then how fast it can go from 6 mph to 15 mph.
Shorter distances equate to better traction. Any
tire that does 110 percent better than an all-sea-
son control tire gets the 3PMSF label.
We chatted with Jonathan Benson, an inde-
pendent tire testing expert and founder of Tyre
Reviews, and he stressed the importance of the
jack-of-all-trades nature of these types of tires.
“The 3PMSF marking doesn’t mean it’s an excep-
tional tire in winter conditions, but it does mean
it has some tested winter capabilities, which is a
step above a non-3PMSF-marked all-terrain tire,”
says Benson. An American-market all-terrain tire,
3PMSF-marked or not, will never match the grip of
a dedicated winter tire.
While the Three-Peak Mountain Snowflake
rating isn’t supremely difficult to achieve, it still
requires some clever engineering where the rub-
ber meets the road. Material properties of the tire
compound can have a profound effect on handling.
Snow tires use a compound that remains pliable at
lower temperatures to extract more grip. However,
this decreases tread life considerably, which is why
a 3PMSF–rated tire like the A/T III has to compro-ANATOMY OF TOYO
OPEN COUNTRY A/T III
To the untrained eye, the Open Country A/T III tires are
nearly identical to any other all-terrain rubber that you’d see
rolling down the road. However, Toyo has optimized the
rubber compound, sipe design, and tread pattern to produce a
tire that meets the Three-Peak Mountain Snowflake rating.November/December 2021 87COURTESY TOYO TIRES