Interpretation ID: nht72-6.32

DATE: 01/04/72

FROM: AUTHOR UNAVAILABLE; Ellwood T. Driver; NHTSA

TO: Recreational Vehicle Institute Inc.

TITLE: FMVSR INTERPRETATION

TEXT: This is in response to your letter of December 21, 1971, relating to the upcoming requirements for GVWR and (Illegible Word) on the vehicle label, under Part 567 of our regulations.

You discussed the difficulties some of your members have had in arriving at the proper values for gross axle weight ratings. To the extent that your discussion highlights the uncertainty that may in the part have existed with respect to the basic load-carrying capacity of vehicle components, it emphasizes the need for the regulation not only as a matter of information but also to ensure the proper design and selection of safety-related components. You asked specifically "what NHTSA would consider to be the requisite test factors which should be utilized for determining wheel ratings." Pending development of performance standards for wheels (or other components), we can only say that the ratings should reflect the manufacturer's own judgement as to the loads that the component can safely carry under the conditions expected to be encountered in use.

The diagrams that you enclosed setting forth basic weighing procedures for determining vehicle and axle loads appear to interpret the regulations correctly.

You mentioned the problem of a possible misunderstanding concerning the measurement of GAWR of a trailer and asked whether the tongue weight may be "deducted from GAWR in arriving at what GAWR should be." The answer is yes, since weight that is carried by the towing vehicle will not be carried by the trailer axle. We should add, however, that GAWR is a rating and therefore may be greater than the actual weight on the axle system when the vehicle is loaded to capacity.

Finally, you requested an "extension of the effective date of the GAWR and GVWR certification requirements to allow time to be sure the industry is advised of the procedure to follow." This request is denied. On the basis of the information available to this agency, it has been determined that our procedures, and the load time between issue and effective date of the regulations, have been fully adequate to allow affected manufacturers to prepare for compliance. Also, by a recent notice published in the Federal Register, we have allowed final-stage manufacturers using incomplete vehicles manufactured before January 1, 1972, for which the weight rating information has not been made available, to omit the GVWR and GAWR values from their labels.