Over-Inflation Data and Analysis:
Out of the 66 vehicles tested at Williams College, 37 had over-inflated tires overall.
The degree of over-inflation for each of these vehicles ranged from 1 pound per square
inch to 96 pounds per square inch, and the total amount of over-inflation was 1,096 pounds
per square inch among the 37 over-inflated vehicles combined (see Appendix H).
Vehicles with over-inflated tires are not analyzed quantitatively because of a lack
of available data and resources; however, their negative environmental impacts are evident.
First, the life expectancies of over-inflated tires are reduced as a result of excess tread
wear. Extrapolating from the 10% decrease in life expectancy for every 10% reduction in
inflation, I speculate that over-inflated tires suffer even more extreme tread wear because
the surface area of the center of the tread, which contacts the road more exclusively for
over-inflated tires, is most likely smaller. That is, since the tire contacts the road only
along the center of the tread when it is over-inflated, and the center of the tread has less
surface area than the entire tread, over-inflated tires must suffer from increased contact in a
more concentrated area and thus more severe tread wear than under-inflated tires or tires
with recommended pressures. Hence, I conjecture that the life expectancy of over-inflated
tires most likely decreases by more than 10% for every 10% increase in inflation. Again,
assuming that tires last nearly 80,000 miles (Tire Aging, 2010), a 15% reduction in life
expectancy would result in a loss of 12,000 miles per tire; a 20% reduction in life
expectancy would result in a loss of 16,000 miles per tire; and so on. With drivers forcing
tires into retirement earlier than necessary, more and more tires are piling up in landfills
and contributing to the problem of unsustainable tire disposal methods.