Interpretation ID: nht87-2.92

TYPE: INTERPRETATION-NHTSA

DATE: 09/14/87

FROM: AUTHOR UNAVAILABLE; Erika Z. Jones; NHTSA

TO: Mr. Y. Osaki

TITLE: FMVSS INTERPRETATION

TEXT: Mr. Y. Osaki Manager, Truck Engineering MMC Services, Inc. 3000 Town Center Suite 501 Southfield, MI 48075

Dear Mr. Osaki:

This responds to your letter asking about the relationship between the maximum load ratings for the tires on a medium duty truck and the gross vehicle weight rating (GVWR) specified for that truck pursuant to 49 CFR Part 567, Certification. Specifically, you asked if the GVWR specified for a truck could slightly exceed the sum of the gross axle weight ratings specified for the truck. While none of our regulations prohibit your company from assigning a GVWR that exceeds the sum of the gross axle weight r atings for this medium duty truck, we recommend that you not do so, for the reasons explained below.

Your letter correctly notes that paragraph @5.1.2 of Standard No. 120, Tire Selection and Rims for Motor Vehicles other than Passenger Cars (49 CFR @571.120) requires that the sum of the maximum load ratings of the tires fitted to each truck axle shall b e not less than the gross axle weight rating (GAWR) for the axle system, as specified on the vehicle certification label required by Part 567. However, Part 567 does not limit the GVWR that can be assigned to the sum of the GAWR's specified for a vehicle . Instead, 5567.4(g)(3) requires that the vehicle certification label specify the GVWR of the truck and requires only that the specified GVWR shall not be less than the sum of the unloaded vehicle weight, rated cargo load, and 150 pounds times the vehicl e's designated seating capacity.

Although, Part 567 does not prohibit such a practice, we note that assigning a GVWR to a vehicle that exceeds the sum of the GAWR's assigned to the vehicle (other than a semitrailer) would be encouraging the user of that vehicle to overload it. If the ax les of a medium duty truck cannot safely bear the load specified in the GVWR, the vehicle will be overloaded whenever it is loaded to the specified GVWR. Such overloading poses a serious safety hazard for the affected vehicle in particular and for the mo toring public in general. Several past interpretations on this subject have stated if a vehicle suffers a hazardous malfunction while in use that can be traced to the overloading of its axle systems, its manufacturer may be liable both under the defect p rovisions of the National Traffic and Motor Vehicle Safety Act and under common law product liability doctrines. To avoid giving rise to a potential safety hazard and the accompanying liability, we recommend that you specify a GVWR not greater than 17,19 6 pounds for the medium duty truck in question.

Sincerely,

Erika Z. Jones Chief Counsel

Ms. Erika Z. Jones Chief Counsel National Highway Traffic Safety Administration U.S. Department of Transportation 400 Seventh Street, S.W. Washington, D.C. 20590

Dear Ms. Jones:

Subject: SPECIFICATION OF GVWR AND MAXIMUM LOAD RATING OF THE TIRES

This is to inquire about the relationship between maximum load rating of the tires and GVW.

We are planning to develop the medium duty truck installing LT235/85R16 tires. According to FMVSS 120.5.1.2, the sum of the maximum load rating of tires fitted to an axle shall not be less than the GAWR of the axle system as specified on the vehicle's ce rtification label.

In our case, the sum of the maximum load rating of LT235/85R16(E) tires are 6,084 lbs. (front) and 11,112 lbs. (rear). TRA So, we can specify at most these values for each GAWR on the certification label as follows:

GAWR: Front - 6,084 with 235/85R16(E) tires 6K rims, at 80 psi cold single GAWR: Rear - 11,112 with 235/85R16(E) tires 6K rims, at 30 psi cold dual

Question: In this case, is it possible for us to specify 17,200 lbs. as GVW on the certification label raising up the fraction, or should we specify 17,196 lbs. strictly?

Your kind advice will be appreciated.

Very truly yours,