Interpretation ID: nht75-2.11

DATE: 11/06/75

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

TO: The Yokohama Rubber Co., Ltd.

TITLE: FMVSS INTERPRETATION

TEXT: This is in response to your letter of August 1, 1975, to Mr. A. Y. Casanova, Office of Crash Avoidance, concerning the rapid loss of air test specified in S4.4.1(b) of Federal Motor Vehicle Safety Standard No. 110.

The test procedure specified in the above cited section of Standard No. 110 requires operating the test vehicle, equipped with the tire and rim combination to be tested, at 60 mph and rapidly deflating the tire. Rapid deflation can be achieved by any method that brings the deflated tire to a full "flat" state while the vehicle is still traveling at 60 mph. Among these methods are:

(1) running the test tire over a V-shaped knife edge,

(2) exploding a small detonation cap to puncture the tire,

(3) evacuating the tire by means of an instrumented vacuum system, and

(4) pulling out the value stem.

Once the tire is deflated, the vehicle is brought to a controlled stop. The tire must remain on the rim.

You specifically asked the position of the beads after the conclusion of the test procedure. The standard requires that the rim retain the deflated tire until the vehicle can be stopped. "Retain the deflated tire" means that the tire beads must be within the rim. The beads need not remain on the bead seat during this test, e.g., one bead may drop into the wall of the rim. However, at no time shall a tire bead be outside of the rim so that the rim is operating on the inside of the deflated tire.

Sincerely,

ATTACH.

June 17, 1975

U. S. Department of Transportation -- National Highway Traffic Safety Administration, Motor Vehicle Programs, Office of Standards Enforcement

Gentlemen:

Please send me one copy of the following publications and if there is a charge please bill us.

1. "Laboratory Procedures for Tire Testing & Data Reporting" latest issue Federal Motor Vehicle Safety Standards 109/117

2. "Laboratory Procedures for Tire Testing & Data Reporting" Federal Motor Vehicle Safety Standards 119

I will look forward to your early consideration of this matter.

Very truly yours,

T. Umeda, Technical Representative -- The Yokohama Rubber Co., Ltd.

August 1, 1975

A. Y. Casanova -- Dept. of Transportation, National Highway Safety Bureau, Office of Operations Systems

Dear Mr. Casanova:

Re: FMUSS #110

As I discussed on the phone, I am very interested in the test procedure concerning the "Rapid Air Loss Test". Please give me more information about this matter.

I would like to especially know the bead position after the test is finished.

Attached please find the letter which I sent to your office on June 17, 1975.

Thank you very much for your kind consideration in this matter.

Very truly yours,

T. Umeda -- Technical Representative, The Yokohama Rubber Co., Ltd.