Interpretation ID: 86-6.6

TYPE: INTERPRETATION-NHTSA

DATE: 12/05/86

FROM: AUTHOR UNAVAILABLE; Stephen P. Wood for Erika Z. Jones; NHTSA

TO: Mr. Kunst

TITLE: FMVSS INTERPRETATION

TEXT:

Mr. Kunst Deutsche Tecalemit Deutsche Tecalemit GmbH P.O.B. 120128 D-4800 Bielefeld 12

Dear Mr. Kunst:

This letter responds to your request for an interpretation of Federal Motor Vehicle Safety Standard No. 106, Brake Hoses. We apologize for the delay in responding to your inquiry. You enclosed drawings of a brake hose end fitting and a vacuum brake hose assembly you manufacture, and asked whether the assembly would conform to the constriction requirements of S9.2.1. In our opinion, the answer is no.

Your letter did not clearly state the size of the inside diameter of the hose used in assembly 90 28B 758. That dimension is necessary in order to ascertain whether constriction requirements are met. We believe, however, based on the markings at the bottom your diagram -i.e., "TUBE 12.5x2.0 DIN 73 37B" - that the brake hose has an outside diameter of 12.5 mm, and a wall thickness of 2.0 mm. The hose would therefore have a nominal inside diameter of 8.5 mm. (If our assumptions are incorrect, please do not hesitate to contact us.) *

Paragraph S9.2.1 of Standard No. 106 states:

Except for that part of an end fitting which does not contain hose, every inside diameter of any section of a vacuum brake hose assembly shall be not less than 75 percent of the nominal inside diameter of the hose if for heavy duty, or 70 percent of the nominal inside diameter of the hose if for light duty.

To pass the constriction test of S9.2.1, a vacuum brake hose assembly (heavy duty) must have an inside diameter that is at least 75 percent of the nominal inside diameter of the brake hose. This, if the nominal inside diameter of the hose is 8.5 mm, the inside diameter of the assembly must be not less than 6.38 mm at any point. If the assembly is intended for light duty, under the 70 percent requirement its inside diameter must be not less than 5.95 mm at any point.

You stated that the inside diameter of end fitting 90 279 346 is 4 mm + 0.5 mm. Because of this size, the part of the fitting which is attached to the hose would not meet constriction requirements of S9.2.1 for either light or heavy duty applications.

If you have further questions, please contact my office.

Sincerely,

Erika Z. Jones Chief Counsel

Chief Council NHTSA 400 7th St. S.W. Washington DC 20590 USA

Subj.: Federal Safety Standards MVSS 106 Paragraph S 9.2.1, Constriction -

Dear Sirs,

In the a. m. matter we wrote to the Office of Vehicle Safety Standards, Crash Avoidance Division, Mr. Stanley R. Scheiner. Today we have received the information from Mr. Scheiner that your office is responsible in this case.

Herewith we would like to give you the following information:

In conjunction with a development for General Motors, we urgently require your interpretation of paragraph S 9.2.1, regarding the constriction of the size of any section of a vacuum brake hose assembly.

As you can learn from the enclosed drawing information, the end fitting 90 279 346 with an inside diameter of 4 mm + 0,5 mm tolerance will be used for the brake hose assembly, drwg. no 90 288 758.

Please confirm that this design comply with paragraph S 9.2.1.

We would deeply appreciate your short term reply.

Yours faithfully

DEUTSCHE TECALEMIT GMBH i.v. Kunst

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