Fatigue, Impairment & Dangerous Behavior

Yes. NHTSA’s data showed that 27% of policyholders from five warm-weather states (Texas, California, Louisiana, Florida, and Arizona) accounted for 77% of all tire-related insurance claims nationwide, and 84% of those claims involved tires older than six years. Tires in hot climates age at rates several times faster than tires in temperate regions because the rate of the oxidation reaction increases exponentially with temperature.

Aged tires fail through two primary mechanisms. Tread separation occurs when the rubber between the steel belts loses its adhesion, causing the tread cap to peel away from the carcass suddenly and without warning at highway speeds. Sidewall blowout occurs when oxidized sidewall rubber fails under the flex loading of each rotation, resulting in immediate and complete loss of air pressure. Both failure modes are often preceded by no visible warning.

Michelin recommends that tires be thoroughly inspected annually after five years of service and replaced 10 years after their date of manufacture, regardless of remaining tread depth, including spare tires. Ford and Chrysler added warnings to their owner’s manuals in 2006 stating that tires should be replaced after six years of service. The British Rubber Manufacturers’ Association recommended that unused tires not be put into service if they are over six years old.

Rubber compounds degrade over time through thermo-oxidative degradation, in which heat and oxygen cause the internal rubber components to stiffen, crack, and lose their ability to flex under load. This degradation occurs whether the tire is in active service or sitting in a warehouse. Oxygen permeating through the inner liner reacts with the rubber compounds even when the tire is not being driven. Spare tires showed degradation patterns similar to on-road tires of comparable age.