Interpretation ID: 86-2.17

TYPE: INTERPRETATION-NHTSA

DATE: 04/09/86

FROM: AUTHOR UNAVAILABLE; Erika Z. Jones; NHTSA

TO: Donald H. Giberson -- Assistant Director, State of New Jersey Division of Motor Vehicles

TITLE: FMVSS INTERPRETATION

TEXT:

Mr. Donald H. Giberson Assistant Director Division of Motor Vehicles Department of Law and Public Safety State of New Jersey 26 South Montgomery Street Trenton, NJ 08666

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 International 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 of motor vehicles or motor vehicle 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 minimum 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 the 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 vehicles 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 issue 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, D.C. 20590 (202-426-2768).

Sincerely,

Erika Z. Jones Chief Counsel

Enclosures

Jeffrey R. Miller, Chief Counsel Office of Rule Making U. S. Department of Transportation National Highway Traffic Safety Administration 400 Seventh Street, S.W. Washington, D.C. 20590

Dear Mr. Miller:

Recently I have received several inquiries regarding the legality of the Mini-Max air actuated mechanically held air brake system judging from the technical data supplied by the manufacturer, International Transquip Industries Inc., the Mini-Max brake chambers do not contain the heavy. Since the heavy spring is omitted and only a single diaphragm is used in the Mini-Max, there is no way the brake can function if the diaphragm ruptures. In view of the foregoing , it is questionable as to whether the Min-Max complies with FMVSS-121 and Motor Carrier Regulation 393.40. I would be appreciative if you could clarify this matter.

Sincerely,

Donald H. Giberson Assistant Director

DHG/WH/rc

Enclosure Omitted.