Interpretation ID: aiam4091
Assistant Director
Division of Motor Vehicles
Department of Law and Public Safety
State of New Jersey
26 South Montgomery Street
Trenton
NJ 08666;
Dear Mr. Giberson: This responds to your request for an interpretation of FMVSS No. 121 *Air Brake Systems*. You asked whether vehicles equipped with 'Mini-Max' brakes, produced by Transquip Industries, Inc., comply with the standard. You stated that since the heavy spring is omitted and only a single diaphragm is used, there is no way the brake can function if the diaphragm ruptures. Your question is responded to below. We note that Motor Carrier Regulation 393.40 is administered by the Bureau of Motor Carrier Safety (BMCS) rather than by the National Highway Traffic Safety Administration (NHTSA). We have sent a copy of this correspondence to BMCS in order that they may respond to that part of your request.; By way of background information, NHTSA does not provide approvals o motor vehicles or equipment. Under the National Traffic and Motor Vehicle Safety Act, it is the responsibility of the manufacturer to ensure that its vehicles or equipment comply with applicable safety standards. The following represents our opinion based on the facts provided in your letter.; Section S5.6.3 provides in relevant part: >>>The parking brake system shall be capable of achieving the minimu performance specified in either S5.6.1 or S5.6.2 with any single leakage-type failure, in any other brake system, of a part designed to contain compressed air or brake fluid (except failure of a component of a brake chamber housing). . . .<<<; The single diaphragm used in the Mini-Max brake is common to both th service and parking brake systems. As part of the service brake system, it is part of a brake system 'other' than the parking brake system. Therefore, since the diaphragm is not a component of a brake chamber housing, section S5.6.3 requires that a vehicle must be able to achieve the minimum performance specified either in S5.6.1 or S5.6.2 in the event of a diaphragm failure.; We do not have sufficient data to determine whether particular vehicle equipped with Mini-Max brakes would meet the requirements of S5.6.1 or S5.6.2 in the event of a diaphragm failure. The answer to that question could depend on the nature of the particular vehicle. It is possible, of course, that a vehicle could be capable of meeting the requirements of S5.6.1 or S5.6.2 as a result of the braking force provided by the other parking brakes whose diaphragms have not failed.; We note that the California Highway Patrol (CHP) has raised this issu and other issues relating to the compliance and overall safety of Mini-Max brakes in connection with a petition for rulemaking, and that International Transquip has submitted comments on CHP's analysis. We have enclosed for your information a notice granting the CHP petition and an interpretation letter to International Transquip. The CHP and Mini-Max submissions have been placed in the Petitions for Rulemaking (PRM) Docket for FMVSS No. 121. If you desire copies of those submissions, please contact: Docket Section, National Highway Traffic Safety Administration, Room 5109, 400 Seventh Street, S.W., Washington, DC 20590 (202-426-2768).; Sincerely, Erika Z. Jones, Chief Counsel