Interpretation ID: nht73-3.6

DATE: 01/03/73

FROM: AUTHOR UNAVAILABLE; E. T. Driver; NHTSA

TO: Office of Operating Systems

TITLE: FMVSS INTERPRETATION

TEXT: Your memorandum of November 27, 1972, concerning non-tabulated values for tire inflation pressures.

In response to the above-captioned memorandum, we, in coordination with the Chief Counsel's office, have concluded that Standard No. 110 does not preclude the use of odd-numbered tire inflation pressures on the placard required by S4.3 of Standard No. 110, and that the standard does not prohibit interpolation of the load values of the Standard No. 109 tables for purposes of compliance testing.

The relevant language of Standard No. 110 is in paragraphs S4.3 and S4.3.1:

S4.3 Placard. A placard, permanently affixed to the glove compartment door or an equally accessible location, shall display the --

(c) vehicle manufacturer's recommended cold tire inflation pressure for maximum loaded vehicle weight and, subject to the limitations of S4.3.1 for any other manufacturer-specified vehicle loading condition . . .

S4.3.1 No inflation pressure other than the maximum permissible inflation pressure may be specified unless --

(b) The vehicle loading condition for that pressure is specified; and

(c) The tire load rating from Table 1 of @ 571.109 for the tire at that pressure is not less than the vehicle load on the tire for that vehicle loading condition.

There is nothing in the standard which specifically requires the inflation pressure to be one actually listed (even-numbered) in the Tables of Standard No. 109. While paragraph S4.3.1(c) of Standard NO. 110, in referring to the load rating found in the table, arguably implies such a requirement, we cannot, without more specific language, read into the standard that recommended inflation pressures must be even-numbered. The mere fact that the specific tire load rating will not be printed in the table, however, does not preclude enforcement of the placard requirement. Because interpolation of values in a table is accepted engineering practice, we conclude that it is reasonable to interpolate such values in the Tables of Standard No. 109, for purposes of enforcing Standard No. 110, where manufacturers have specified odd-numbered inflation pressures.