Tire rule would exclude large trucks

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The National Highway Traffic Safety Administration in late July proposed to require tire pressure monitoring systems in new passenger cars and in new light trucks and multi-purpose passenger vehicles. The proposed rule, mandated by legislation enacted last year, applies to motor vehicles, except motorcycles, with gross vehicle weight ratings of 10,000 pounds or less.

NHTSA is considering two alternatives for the new standard. One would require that the driver be warned when the tire pressure in one or more tires, up to a total of four tires, has fallen to the higher of (1) 20 percent or more below the vehicle manufacturer’s recommended cold inflation pressure for the vehicle’s tires or (2) a minimum level of pressure to be specified in the new standard. The other alternative would require that the driver be warned when tire pressure in one or more tires, up to a total of three tires, has fallen to the higher of (1) 25 percent or more below the vehicle manufacturer’s recommended cold inflation pressure for the vehicle’s tires or (2) a minimum level of pressure to be specified in the new standard.

In issuing the notice of proposed rulemaking, NHTSA said it is not proposing to require TPMS on medium or heavy vehicles for several reasons. First, a law passed in response to the Firestone recall mandates the rule. That recall was limited to light vehicles, so NHTSA has focused its study of under-inflation on light vehicles. Also, the issues associated with under-inflated tires on medium and heavy vehicles are different from and more complex than those associated with under-inflated tires on light vehicles, NHTSA says. The agency notes, for example, that medium and heavy vehicles are equipped with tires that are much larger and have much higher pressure levels than the tires used on light vehicles. The number of axles and tires complicates matters as well.

Finally, the Federal Motor Carrier Safety Administration is addressing tire maintenance issues on heavy, but not medium, vehicles. FMCSA plans to conduct a comprehensive study, including possible fleet evaluations of different systems, of all the issues related to improvement of heavy vehicle tire maintenance. NHTSA said that it plans to coordinate with the FMCSA to address the issues associated with heavy vehicle tire maintenance and that it will work with FMCSA to examine the desirability of proposing a TPMS standard for heavy vehicles. NHTSA also will consider the implications of the results of that examination for medium vehicles.

For more details on NHTSA’s proposal, visit http://dms.dot.gov/search and search Docket No. 8572.