Interpretation ID: nht72-5.42

DATE: 03/01/72

FROM: AUTHOR UNAVAILABLE; Francis Armstrong; NHTSA

TO: Avis M. Hicks

TITLE: FMVSR INTERPRETATION

TEXT: This is in reply to your letter of December 14, 1971, in which you ask certain questions relating to "Gross Vehicle Weight Rating" (GVWR) as it would apply to our regulations, 49 CFR 567 and 568. Our requirement that certain weight ratings be applied to a label by vehicle manufacturers is a regulation and not a Federal motor vehicle safety standard.

Gross vehicle weight rating as defined in @ 568 of the regulations "means the value specified by the manufacturer as the loaded weight of a single vehicle." This was further clarified in the Federal Register on October 8, 1971, 36 (Illegible Words) "To preclude the possibility of understating a vehicle's GVWR, however, the certification regulation is herewith amended to provide that the stated GVWR shall not be less than the sum of unloaded vehicle weight, rated cargo load, and 150 pounds times the vehicle's designated seating capacity." Unloaded vehicle weight has been defined as ". . . the weight of a vehicle with maximum capacity of all fluids necessary for operation of the vehicle, but without cargo or occupants," 36 FR 2511.

From the standpoint of the regulation itself, the only other limit on GVWR would be that it should not be more than the sum of the gross axle weight ratings (although it may be less), since otherwise the vehicle would obviously be supplied with axle systems inadequate for its carrying capacity.

Good engineering practice would dictate that weight ratings be based on the weakest component in the system regardless of what it, the weakest component, might be. Of course, weight distribution is one of the factors that must be considered in making these calculations. In the example you have cited, if a manufacturer supplied a rear axle on his vehicle with a stated axle weight rating of 13,000 pounds with tires on the axle having a sum total rating of something less he would be overstating the GVWR of a particular axle on his certification label. GVWR's should not be greater than the total tire capacity or as stated before the sum of the gross axle weight ratings.

If you have further questions, I will be pleased to answer them.