TPMS Risks of Under/Overinflation

1.1: Risks of Under/Overinflation

Proper tire inflation is important for several reasons. According to the Rubber Manufacturers’
Association, underinflation is the most common cause of tire failure.1 Underinflated tires experience a
greater amount of sidewall flexion than properly inflated tires, resulting in decreased fuel economy,
sluggish handling, longer stopping distances, increased stress to tire components, and heat buildup that
can lead to catastrophic failure of the tire, such as cracking, component separation, or blowout.2 These
catastrophic failures can cause loss of vehicle control and may result in a crash. Overinflated tires may
be more easily damaged by potholes or debris. Severe overinflation may increase stopping distance due
to reduced area of road contact and non-optimal traction, and may also contribute to vehicle instability.
As with underinflation, overinflation may result in uneven tread wear that reduces the useful life of the
tire.
This report evaluates the effectiveness of tire pressure monitoring systems (TPMS) in reducing the
frequency of severely underinflated tires by using survey data acquired through the Tire Pressure
Monitoring System – Special Study (TPMS-SS), specifically designed for this purpose. (Future analyses
are planned to estimate the effect that TPMS has on crash avoidance and mitigation, based on realworld
crash data.) Statistical survey sampling techniques were used to generate a nationally
representative sample of passenger vehicles of model years 2004-2011. The TPMS-SS collected data on
6,503 vehicles at gas stations throughout the United States from August 2010 through April 2011. Over
90 percent of these observations (n = 6,103) were complete enough to include in analyses of TPMS
effectiveness. The basic method of analysis was to compare under- and overinflation rates observed in
vehicles with and without TPMS. The magnitude of the difference in these rates formed the estimates
of TPMS effectiveness.