A tire detread is not a blow-out. A blow-out occurs when the air in a tire literally blows out of the tire. A detread, however, occurs when the tire’s tread separates from the rest of the tire while the carcass of the tire still maintains its air. A blow-out causes an abrupt pull to the vehicle side of the blow-out and a sudden loss of speed, because the rim interacts with the roadway. A detread only very slightly affects vehicle speed and pulls a vehicle to the side of the detread with far less force than a blow-out. But, with a detread, a driver has lost traction under the detread side of the vehicle. A front axle detread, without braking or steering, will exponentially pull the vehicle to the side of the detreaded tire. If a detread occurs on the rear axle, the tire’s increased drag during separation causes a slight vector change. A driver will typically counter-steer from the change of direction. With this steering maneuver, the vehicle is dependent on its rear wheels. Without traction on the tire from which the driver most needs it, the vehicle’s lateral stability becomes compromised. In sport utility vehicles and light trucks, the vehicle may transfer from an understeer vehicle to an oversteer vehicle, virtually eliminating a driver’s ability to control the vehicle. Detreads are much more dangerous than blowouts.
A detread can occur in several places. A tire is constructed with an inner liner, body plies, steel belts, and a tread (sidewalls, also). A detread is the result of a long migration of air from a very small separation between the four layers of a tire. A separation may start between the steel belts – most tires have two belts. A separation may be located between the plies and the first steel belt. Regardless of location or how it started, the air within the separation migrates toward higher pressure, or the outside of the tire. As the separation grows, the tire’s bond between the components is increasingly compromised. For example, if the bond between the steel belts is failing, the belts start to peel apart. More specifically, the top belt and tread would begin to peel away from the bottom belt and the rest of the tire. Once that peeling begins, centrifugal force created during operation causes the peel to get longer. From the driver’s perspective, the vehicle mostly experiences no discernable difference, until the tread starts slapping the wheel-well of the detreading tire. This slap sound gets louder and faster, until the tread separates fully from the tire. The slapping tread creates a drag, very slightly altering the vehicle’s vector. From this point, the entire detread accident may only take two seconds. With drastically compromised lateral stability, the tire will yaw, or drag sideways as the vehicle fishtails initially toward the detreaded tire.
In comparison to tire blowouts, tire detreads are exceedingly rare. Drivers may have personal experience or classroom knowledge of what to do when experiencing a tire blowout, but 99.9999% of drivers have no information of how to respond to a tire detread. Regardless, the forces asserted on the vehicle during a tire detread are much more complex than those associated with a blowout. A detread is a very rare but very dangerous occurrence.
Written by:
Guy L. Watts, II
Watts Guerra LLP
4 Dominion Drive, Bldg 3, Suite 100
San Antonio, Texas 78257
Phone (210) 447-0500
© Watts Guerra LLP 2015
