Interpretation ID: 77-3.29

TYPE: INTERPRETATION-NHTSA

DATE: 07/15/77

FROM: AUTHOR UNAVAILABLE; R. L. Carter; NHTSA

TO: Patton, Boggs & Blow

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your April 20, 1977, petition to amend Standard No. 120, Tire Selection and Rims for Motor Vehicles Other Than Passenger Cars. In your petition, you request that the National Highway Traffic Safety Administration (NHTSA) permit the use of tires that have a maximum load rating of not less than 95% of the gross axle weight rating (GAWR) and not less than 95% of the gross vehicle weight rating (GVWR). Your petition is denied.

The problem addressed by your petition concerns a revision in the 1977 Tire and Rim Manual that alters the load rating of tires. In effect, this revision will result in lower load ratings for certain tires. According to the facts you submit, the change in tire load rating will be implemented by tire manufacturers throughout the next few months which may not provide vehicle manufacturers sufficient time to correspondingly alter the GAWRs of their vehicles in accordance with the new tire load ratings. Therefore, for a short period of time, you allege that it will be impossible to obtain tires that correspond to the GAWR indicated on the vehicle.

To alleviate the above problem, you recommend rulemaking that would permit vehicle manufacturers to install on their vehicles tires with load ratings slightly less than the GAWR of each axle. The NHTSA cannot permit the relief you request even for the limited time you propose. The intent of our tire standards is to provide minimum requirements for tires to ensure adequate safety. One of these minimum requirements mandates that the tire load rating be at least equal to the GAWR. Your request would have us reduce this minimum requirement. Since the matching of tires on a vehicle with the GAWR of each axle is such a basic principle of safety, the agency concludes that it would not be in the interest of safety to grant your request. Further, such an amendment might violate Section 202 of the National Traffic and Motor Vehicle Safety Act (15 U.S.C. @ 1381 et seq.), which requires that motor vehicles be equipped "with tires which meet the maximum permissible-load standards when such vehicle is fully loaded. . . ."

As you may know, the label requirements of Standard No. 120 which become effective in September permit you to list suitable tire and rim combinations on the vehicle. You need not equip a vehicle, however, with the tires indicated on the label. In this case, you may equip a trailer with any trailer tire that has a load rating equal to or greater than the GAWR of its associated axle. This may help resolve part of your problem with respect to a short term problem with matching tires on the vehicle with those indicated on the vehicle label.