Interpretation ID: 77-2.18
TYPE: INTERPRETATION-NHTSA
DATE: 04/28/77
FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA
TO: ASTM Subcommittee F9.10
TITLE: FMVSS INTERPRETATION
TEXT: This responds to your March 2, 1977, letter asking whether the National Highway Traffic Safety Administration (NHTSA) still emphasizes or frequently conducts tubeless tire resistance to bead unseating tests as authorized by Standard No. 109, New Pneumatic Tires.
As you know, the bead unseating test procedure was adopted from the Society of Automotive Engineers Practice J918. It is our understanding that the SAE continues to use this procedure for tire performance tests. The NHTSA is of the opinion that the bead unseating test procedure is a viable laboratory evaluation of the compatibility of a tire and rim combination. This has become especially important since 1975, when the table of approved alternative rims of Appendix A of Standard No. 110, Tire and Rim Selection, was deleted, and the tables of standards organizations were adopted. The bead unseating test provides an additional verification of the tire and rim combinations listed in the yearbooks of these organizations.
Standard No. 109 requires several tire performance tests: physical dimensions, resistance to bead unseating, strength, endurance, and high speed performance. The NHTSA compliance testing is conducted on a random selection basis. In the case of tires, not every test is conducted on each brand of tire selected for compliance testing. Therefore, the bead unseating test is not always conducted during compliance testing. However, the agency does conduct bead unseating tests whenever appropriate and will continue to do so.
SINCERELY,
ASTM
March 2, 1977
Chief Counsel National Highway Traffic Safety Administration
The ASTM Subcommittee F-9.10 on the Structural Integrity of Tires has been developing a Standard Test Procedure for Unseating the Bead of a Tubeless Passenger Car Tire from the Rim. The draft of this Proposed Standard Test Procedure was approved by the Subcommittee and submitted to the F-9 Main Committee for ballot. The Test Procedure is essentially that of the Bead Unseating Test contained in the National Highway Traffic Safety Administration test MVSS 109 put in ASTM format.
Discussion of five negative ballots which were received disclosed that there exists considerable doubt concerning the validity of the Bead Unseating Test among the engineers representing the tire producing companies. The principal objections to it are:
a. It is believed that the unseating test does not reflect actual field results, nor performance characteristics.
b. The test is not functional for all current sizes (profiles, construction, etc.) of tires.
c. The origin and data base of the bead unseating test, as well as the reasons for its incorporation into the repertoire of testing, are not clear to the persons presently involved in tire test work.
d. That the regulatory bodies no longer emphasize nor do they frequently conduct the test.
The Task Group is planning a survey to obtain information from the tire producing companies which will assist in the resolution of (a) and (b) above. Since the test originated with the motor car companies and was developed by their representatives in the tire committee of the Society of Automotive Engineers, the Task Group expects to obtain the early history of the test from the SAE group to resolve (c).
It is the purpose of this inquiry to the National Highway Traffic Safety Administration to determine whether that regulatory group no longer emphasizes nor frequently conducts the test as stated in (d) above. Is this the present situation? Does NHTSA consider that this test has lost significance since it was adopted as part of the original MVSS 109.
The ASTM Subcommittee F-9.10 would appreciate a response from NHTSA to clarify the situation in which the passenger tubeless tire bead unseating test is presently considered and conducted by them.
Louis Marick, Chairman Subcommittee F-9.10
ASTM
March 2, 1977
Chief Counsel National Highway Traffic Safety Administration
Enclosed is a copy of a letter from ASTM subcommittee F9.10 on the Structural Integrity of Tires questioning the validity of the "Bead Unseating Test Procedure MVSS109" which is being considered for development as an ASTM Standard.
The purpose of my letter is to request your response to the problem presented and ask that you reply directly to:
Mr. Louis Marick, Chairman ASTM Subcommittee F9.10 339 Merriweather Road Grosse Pointe, Mich 48236 Your assistance on this standards development project will be sincerely appreciated.
William T. Cavanaugh Managing Director
CC: L. MARICK; F. CECIL BRENNER -- NHTSA