A studded tire report was commissioned by the
state of Washington to
learn how well they worked. We review their findings....
Study Of Studded Tires For Traction And Safety
The state of Washington commissioned a study of Studded Tires to
determine how effective they were in improving traction and safety. The
Studded Tire Report was published in November
Summary of the Studded Tire Report
The report is an extensive review of research on the performance and
safety of Studded Winter Tires (SWTs). While it recognizes the
negative impact of studs in tires on pavement, the report focuses on
the performance of late-model vehicles equipped
with current generation of SWTs, as well as those equipped with
“studless” winter tires such as the “Blizzak” design made by
SWTs have been controversial for years.
have banned them, while others restrict their use. (Studded tire Regulations).
Many issues surround the use of studs in tires
the advantages and disadvantages of improved icy-road
traction performance versus the cost of pavement damage.
how to define traction performance
the conditions under which SWTs are compared with
the "safety" of SWTs as measured by traffic
driver behavior while using SWTs based on drivers'
perception of safety
secondary effects, including
dust from road wear
reduced vehicle control on roadways rutted by stud wear
the potential for improved traction characteristics on
roadways "roughened" by studded tire use
the cost of SWTs in comparison with new
studless winter tires
the increase in fuel consumption for studded versus
the possible trade-off in the use of traditional
Studded tires produce their best traction on snow or ice
near the freezing mark.
SWTs give better traction than studless tires only
under a narrow range of conditions.
The conditions under which SWTs give better
traction relatively rare.
Traction improvements can be looked at many ways, including
acceleration, cornering, controllability, and hill climbing. While
these are all important, the single best indicator of tire performance
is braking distance and
SWTs reduce the difference in friction factor
between optimum-slip and
locked-wheel braking in comparison to non-studded tires. This may
risk of drivers misjudging the necessary braking distance and may
braking potential for anti-lock brakes.
In one set of stopping distance tests in Alaska, studded,
studless, and all-season
tires performed nearly equally on snow.
In another set of tests in Alaska, studless Blizzak tires
offered the best traction
performance, especially for braking on both packed snow and ice in
to studded tires.
The use of two SWTs on the front of a vehicle
produced stopping traction
results on snow and ice that were about halfway between the result of
SWTs and four all-season tires. However, other control
problems such as spinning sideways arise.
On bare pavement, studded tires tend to have poorer
traction performance than
other tires. This is especially true on concrete; for asphalt, there is
difference in stopping distance between studded and non-studded tires.
The traction of SWTs is affected by stud wear. As
the studs wear and become shorter traction decreases until the benefit
practically disappears when the stud protrusion diminishes to 0.024 in.
(0.6 mm). On the other hand the tread wear (on studded tires) shows
relatively little effect if stud protrusion is maintained at 0.039 in.
to 0.043 in. (1.0 to
In Norway a study concluded that the use of SWTs
could to reduce the
accident rate between 1 and 10 percent .
Driver behavior issues have been raised which affect the
evaluation of SWTs. There is disagreement on these points:
drivers with SWTs care more about safety,
hence they drive more safely
they drive faster (because of a false sense of security
drivers with non-studded tires avoid driving when
weather is severe
Pavement ruts caused by increased wear from studded tires
can cause the
dangerous conditions of trammeling, hydroplaning on accumulated water
ruts, excessive road spray, and premature damage to pavement markings.
The roughening of ice and pavement from SWTs
provides a safety benefit
for all vehicles regardless of weather or not they use studs by helping
to prevent formation of smooth, glare ice.
The cost of studless tires is significantly higher than SWTs
approximately 50 percent.
SWTs increase fuel consumption by about 1.2 percent
compared with non-studded tires on bare roadways. But the other effects
of unevenness, snow,
and ice which can increase fuel consumption by as much as 15 percent
are far more significant than this.
Pavement dust created by studded tires and noise from
studded tires are concerns in high traffic urban areas.
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