Interpretation ID: nht80-3.19
DATE: 07/14/80
FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA
TO: Michelin Tire Corporation
TITLE: FMVSS INTERPRETATION
TEXT: This responds to your June 10, 1980, letter requesting an interpretation of the appropriate tire size markings required to appear on a vehicle's certification label by 49 CFP. Part 567. More specifically, you stated that Michelin intends to supply truck tires to an American truck manufacturer labeled with the tire size designations set forth by the International Standardization Organization (ISO).
Michelin listed the following as an example of an ISO size designation: 275/80R22.5 143/140K. The labeling in that example would not comply with the requirements of Standard 119 (49 CFR @ 571.119), so the tire manufacturer, Michelin in this case, would be permitted to sell tires with only that labeling. Further, any truck manufacturer citing tire information in this manner on its certification label would be violating Standard 120 (49 CFR @ 571.120) and Part 567.
Paragraph S6.5 of Standard 119 specifies that all tires for vehicles other than passenger cars must have certain markings on the sidewalls. Among other things, these tires must show the actual number of plies in the tire, the composition of the ply cord material (S6.5(f)), and a letter designating the load range (S6.5(j)). As you stated in your letter, the ISO designation does not show the number and composition of the plies and, therefore, does not satisfy this requirement of Standard 119. You further stated in your letter that the 143/140 designation in the ISO marking shows the load carrying capacity of the tire. In the ISO system, the letter K denotes the speed rating for the tire, and not the load carrying capacity. Standard 119 explicitly requires a letter marking to denote the load range of the tire and your proposed use of the ISO marking fails to satisfy that requirement also.
The vehicle manufacturer is required by paragraph S5.3 of Standard 120 to affix a label to the vehicle providing information on appropriate tires and rims for the vehicle. Similarly, 49 CFR @ 567.4 requires a vehicle manufacturer to list a suitable tire size after the gross axle weight rating (GAWR) on the vehicle certification label. Subparagraph S5.3.1 of Standard 120 requires the label to include the size designation of tires appropriate for the GAWR.
To list the tire size designation appropriate for the GAWR, the vehicle manufacturer must list more than the dimensions of the tire (e.g., 7.50-20 in the truck example following S5.3 in Standard 120). This is because many truck tires have identical dimensions, but widely varying load carrying capacities. For instance, the 7.50-20 size tire comes in load range D, F, and G, with its load carrying capabilities ranging from 2,750 pounds for load range D up to 4,150 pounds for load range G. Thus, for the vehicle manufacturer to comply with the requirement that it show an appropriate tire size, the manufacturer must show both the dimensions and the load range of the appropriate tires.
The reason for requiring the vehicle manufacturer to list appropriate tires for the vehicle is to give the vehicle user a permanent and useful record of the tires that can safely be used on the vehicle. If a vehicle manufacturer were to use an ISO designation to indicate the load range of those tires, the user of the vehicle would be given information different from the letter designations which are required by Standard 119 to appear on the tires. Since needless confusion could arise from this situation, and this confusion would impair the purpose of the tire information labels, Standard 120 and Part 567 necessarily require that the load carrying capabilities of the tires be expressed in terms of a letter, as specified in Standard 119.
SINCERELY,
REF: PART 567
MICHELIN TIRE CORPORATION -- Technical Group
10 June 1980
Chief Counsel U.S. Department of Transportation National Highway Traffic Safety Administration
Ref: Part 567 Certification
Dear Sir:
We intend to supply truck tires to an American truck manufacturer with size designations according to the standards of the International Standardization Organization (I.S.O.). An example of such a size marking is:
275/80R22.5 143/140K
You can see that there is no ply rating in this designation; the load carrying capacity being designated instead by the load index 143/140. These load indices have been established by the I.S.O.
As you know, Part 567 requires that truck manufacturers list a suitable tire size after the GAWR on the certification plate. We do not see anything in the regulations that would prohibit listing a tire with the I.S.O. size designation. However, the truck manufacturer has requested that we confirm that listing such a tire will be in accordance with D.O.T. regulations.
We are therefore requesting your written confirmation in this regard.
Your prompt attention to this request would be appreciated.
John B. White Engineering Manager Technical Information Dept.