Interpretation ID: nht80-3.25
DATE: 07/30/80
FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA
TO: Michelin Tire Corporation
COPYEE: R. McCUTCHEON -- ASST. POSTMASTER GEN., U.S. POSTAL SERV.
TITLE: FMVSS INTERPRETATION
TEXT: In your June 5, 1980, letter to this office, you indicated that Michelin would like to equip mail vans with passenger car tires. Since the mail vans will be restricted to speeds of 50 miles per hour and less, you believe that it would be permissible to load the tires above the maximum load indicated on the tires, pursuant to the provisions of Standard 120 (49 CFR @ 571.120). This assumption is accurate.
Section S5 of Standard No. 120 sets forth two basic safety requirements which new motor vehicles other than passenger cars must meet, including a mail van. Paragraph S5.1.1 requires these vehicles to be equipped with tires which meet the requirements of Standard 109 or Standard 119. From your characterization of the tires as passenger car tires, I assume that you will be providing tires which meet the requirements of Standard 109.
The second general requirement, contained in paragraph S5.1.2, is that the sum of the maximum load ratings of the tires fitted to an axle shall be not less than the gross axle weight rating (GAWR) of the axle system, as specified on the vehicle's certification required by 49 CFR Part 567. As you implied in your letter, this requirement of S5.1.2 does not apply to vehicles which have a speed attainable in 2 miles of 50 miles per hour or less. This exception was intended to apply only to vehicles such as mobile cranes, which do not have the capability to reach speeds greater than 50 miles per hour. However, the language inadvertently is so broad that it encompasses vehicles which have their speed capabilities restrained by devices like governors and, thus, would apply to the mail vans you describe.
There are two comments I would like to make on this unintended loophole. One is that we will strictly enforce the 50 mile per hour limitation. If any of the mail vans can attain speeds over 50 miles per hour, that van will be in violation of Standard 120 if the tires you describe are used. Additionally, we are going to examine whether it is necessary to amend Standard 120 to close this loophole.
The second comment is a recommendation that you fit the mail vans with tires whose labeled maximum loads are at least equal to the GAWR of the axle on which they are mounted. The Tire & Rim Association allows a 9 percent increase in the load over the maximum load labeled on the tires when the speed range is restricted to 50 miles per hour (1979 Yearbook of the Tire & Rim Association, at 2-03). This 9 percent increase in load carrying capacity is calculated for truck tires. When using passenger car tires on the mail vans you have described, safety concerns mandate that the load carrying capacity of the tires be reduced by 10 percent, to ensure that the lighter duty passenger car tires can safely perform the heavier duty work that is routine for vehicles like mail vans. Indeed, if the vehicles were not speed restricted, S5.1.2 of Standard 120 would require this 10 percent reduction to be made for the passenger car tires.
If Michelin follows the course of prudence, it should calculate the maximum load carrying capacity of the tires with a 9 percent increase allowed for the speed restriction. Then this maximum load must be reduced by 10 percent to allow for the use of passenger car tires. The net result of this increase and decrease would be that the maximum load which the passenger car tires you describe could safely carry is approximately the maximum load labeled on the tires, because the increase and decrease will cancel each other out.
I trust that Michelin Tire Corporation, which has a very good record of concern for tire safety, will not equip a motor vehicle with potentially unsafe tires, even if a loophole in Federal regulations might inadvertently permit it to do so.
SINCERELY,
REF: D.O.T. MISC.
MICHELIN TIRE CORPORATION - Technical Group
JUNE 5, 1980
Office of Chief Counsel U.S. Department of Transportation National Highway Traffic Safety Administration
Gentlemen:
We are proposing the use of a passenger tire on an electric mail van being produced for the U.S. postal service.
The van is speed restricted to 50 mph, therefore, we can allow an increase in load carrying capacity over and above that indicated on the tire sidewall.
If the van is considered "a vehicle other than a passenger car" it would fall under the requirements of FMVSS 119 and 120 rather than FMVSS 109 and 110 and the increase in load carrying capacity would be in accordance with FMVSS 119 and 120.
Please advise if our proposed solution is in conformance with NHTSA requirements.
The scheduling of this program is extremely tight and your prompt reply would be appreciated.
John B. White Engineering Manager Technical Information Dept.