TIA has ´serious concerns´ about TPMS rule

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The Tire Industry Association (TIA) believes that the new tire pressure monitoring system (TPMS) regulation proposed earlier this week "does not fulfill the requirement of improving safety for motorists."

Under the rule, new vehicles must be equipped with a TPMS capable of detecting any tire that is inflated 25% below the recommended inflation pressure established by the vehicle manufacturer.

"We have serious concerns about the threshold where the system would notify the driver of an underinflated tire," says TIA Executive Vice President Roy Littlefield.

"For example, a car with a gross axle weight rating of 1,885 pounds on the front axle has a recommended cold inflation pressure of 32 psi, which can support 1.058 pounds per tire. If the 25% threshold is used, the resulting air pressure is 24 psi, so the carrying capacity of the tire will be less than 900 pounds per tire, thereby creating a potentially overloaded assembly.

"If a 20% threshold is used, the resulting air pressure is 26 psi, so the tire can support a load of 959 pounds. In this instance, a system that enacts at 20% would notify the driver that a potentially unsafe condition is about to occur. However, as soon as the inflation pressure drops below 26 psi, the tire can no longer support the gross axle weight rating, or the maximum weight on the front axle.

"If the new proposed threshold of 25% is adopted, the driver could be driving on an overloaded tire for a significant period of time."

TIA officials maintain that the 25% will not work on every vehicle. "Drivers of vehicles with TPMS will naturally have an improved sense of security as long as the sensors do not indicate an underinflated tire," they say.

The association also believes that the proposed rule does not adequately address the issue of reserve load.

"Given the serious concerns over the threshold where the system notifies the driver and the lack of current information on the importance of reserve load, we feel that the current proposal does not take all factors into consideration and will still result in vehicles being operated with tires that cannot support the load," concludes Littlefield.

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