You may think that the greatest limit on the speed of your vehicle is the power produced by the engine. You know that the faster velocity, the more horsepower you need to overcome resistance from the air and the weight of your car or truck. But there is another limit, which you hope never to encounter, that of the speed rating of your tires.
Higher speeds place great stress on tires, as they roll across the surface of the road. They get hotter, which increases the internal air pressure of the tire and places a greater stress on the structural integrity of the tire. It also creates a greater risk of a blowout if the tire strikes debris in the road.
But even inexpensive car tires are now speed rated to 112 miles per hour. This is not true of truck tires; most are speed rated only to 75 mph. Which means if a truck drives at that speed for extended periods, it could suffer a catastrophic blowout, endangering the driver’s life and that of any vehicle near the truck when it suffers such a tire failure.
In the western half of the U.S., many states have 75 mph speed limits on interstates and a few even allow 80 mph traffic. While Pennsylvania does not allow traffic to drive at this speed, we all have seen trucks traveling this fast.
A federal agency examined a group of truck accidents involving tire failures and determined that they were all due to driving too fast. Proposals for regulating speed of all truck by electronic controls has been delayed for years, as various groups argue about the cost and whether it would be effective.
All truck drivers should know the speed ratings on his or her tires and operate their vehicle accordingly, but the constant pressure to deliver on time means they may not use their best judgment.
Denverpost.com, “Danger linked to big rigs burning rubbe,” Tom Krisher, Associated Press, April 5, 2014