Interpretation ID: nht78-2.38

DATE: 09/21/78

FROM: AUTHOR UNAVAILALE; J. J. Levin, Jr.; NHTSA

TO: The B. F. Goodrich Company

TITLE: FMVSS INTERPRETATION

TEXT: This responds to B. F. Goodrich's August 2, 1978, question whether the specified temperature for brake burnish in S6.1.8.1 of Standard No. 121, Air Brake Systems, should be maintained by reducing maximum vehicle speed during snubs even if the reduced maximum speed does not appear among the snub conditions listed in Table IV of S6.1.8.1.

The answer to your question is yes. The snub conditions listed in Table IV represented the agency's best estimate of appropriate speeds for obtaining the specified burnish temperature, given the state-of-the-art of brake technology when the standard was issued. If you have under development a brake design that achieves the specified burnish temperature at a lower speed, it would be correct to reduce vehicle speed below the 40-mph level specified in Table IV to achieve and maintain that temperature.