Mr. Robert O. Martin
Division Vice President
Corporate Quality Assurance Division
50 Century Boulevard
Nashville, TN 37214
Dear Mr. Martin:
Please pardon the delay in responding to your letter addressed to Walter Myers of my staff, in which you asked whether you may install light truck (LT) metric tires that comply with Federal motor vehicle safety standard (FMVSS) No. 119, New Pneumatic Tires for Vehicles Other Than Passenger Cars, and No. 120, Tire Selection and Rims for Motor Vehicles Other Than Passenger Cars, on a "Presidential Limo" that you describe as "basically a modified passenger vehicle." The installation of LT tires would not be permitted on a passenger car under the provisions of FMVSS No. 110, Tire Selection and Rims.
NHTSA defines a "passenger car" as "a motor vehicle. . ., except a multipurpose passenger vehicle, motorcycle, or trailer, designed for carrying 10 persons or less." A "multipurpose passenger vehicle" (MPV) is one designed to carry 10 persons or less but which "is constructed either on a truck chassis or with special features for occasional off-road operation." Finally, a motor vehicle, except a trailer, designed to carry more than 10 persons is classified as a bus.
You did not specify the original vehicle that you modified to create the presidential limo, other than to call it a modified passenger vehicle, nor did you describe the modifications you made to it. All the vehicles described in the previous paragraph are passenger vehicles, but each has different functions, classifications, and requirements. Thus, the classification of the basic vehicle determines which set of tire requirements apply to it.
If you "stretched" a passenger car, for example, or if you modified a passenger car other than by stretching it, the issue then becomes whether the vehicle as modified is still a passenger car or whether it should be recertified as a different type of vehicle. If it still carries 10 persons or less or if it has not become an MPV, it retains its classification as a passenger car. Paragraph S4.1 of FMVSS No. 110 states that passengers cars must be equipped with tires that meet the requirements of FMVSS No. 109, New Pneumatic Tires. Installation of tires certified as complying with FMVSS No. 119 is not permitted on passenger cars because of the high speed performance test required of passenger car tires but not of LT tires. Specifically, paragraph S18.104.22.168 of FMVSS No. 109 requires that passenger car tires be subjected to a high speed test, while paragraph S6.3 of FMVSS No. 119 applies the high speed test only to motorcycle tires and "non-speed-restricted tires of 14.5-in nominal rim diameter or less marked load range A, B, C, or D." We can assume that a stretched limo, in at least a few situations, may be driven at high speeds. If, on the other hand, the original vehicle was certified as an MPV, truck, or bus, FMVSS No. 120 specifies that tires that comply with either FMVSS Nos. 109 or 119 may be installed on it, provided that if passenger car tires under FMVSS No. 109 are installed on it, they would be subject to the 10 percent load rating correction factor specified in paragraph S5.1.2 of FMVSS No. 120.
I hope this information is helpful to you. Should you have any questions or require any further information, please feel free to contact Mr. Myers at this address or at (202) 366-2992.
Acting Chief Counsel