International Tire Marketers
358 West Heber Street
Glendora, CA 91741
Dear Mr. Phillips:
This responds to your letter of June 21, 1995, in which you asked us to update your information on new tire sizing codes used in the DOT identification of tires. Please be advised that this agency no longer specifies tire size codes.
49 Code of Federal Regulations (CFR) '574.5, Tire identification requirements (copy enclosed), requires tire manufacturers to label on one sidewall of each tire it produces a tire identification number (TIN), and specifies that the TIN will be composed of four groupings, the second of which "shall be used to identify the tire size."
The size requirement in the TIN was first promulgated as '574.4 on November 10, 1970 (35 FR 17257). At that time, NHTSA (then the National Highway Safety Bureau) specified in Table 1 of the regulation the codes to be used to designate the various tire sizes. In the following two years, the agency amended Table 1 numerous times to add new codes to represent additional tire sizes. On November 8, 1972 NHTSA published a final rule rescinding Table 1 and the agency-specified tire codes (37 FR 23727). The agency explained that because of the many new tire sizes being introduced, available new codes had become exhausted and it was necessary to change the system to one permitting greater flexibility. Accordingly, the agency amended the regulation to permit manufacturers to assign their own two-digit code to represent tire size and to permit retreaders to use either a self-assigned matrix code or a self-assigned tire size code. The November 8, 1972 amendment also required each new tire manufacturer and retreader to maintain a record of each symbol used and provide that information to NHTSA upon written request. Those requirements remain in effect (49 CFR '574.5(b)).
In summary, 49 CFR '574.5 no longer specifies tire size codes for use as the second grouping of symbols in TINs. Rather, the regulation permits manufacturers and retreaders to use their own tire size codes in that grouping of the TIN.
I hope this information is helpful to you. Should you have any further questions or need additional information, please feel free to contact Walter Myers of my staff at this address or at (202) 366-2992.
John Womack Acting Chief Counsel