Interpretation ID: 2742y
Project Engineer, Drum Brakes
Bendix Automotive Systems
Allied-Signal, Inc.
P.O. Box 4001
South Bend, IN 46634-4001
Dear Mr. Rusk:
This responds to your recent inquiry concerning adjustment procedures for hydraulic brakes during testing in accordance with Federal Motor Vehicle Safety Standard No. 105; Hydraulic Brake Systems. You asked whether, following the revisions effective September 1, 1991, the Standard will authorize manual brake adjustment on a vehicle equipped with duo-servo brakes and automatic brake adjusters following the initial burnish and three subsequent reburnishes. Although your letter did not specify that the focus of your inquiry is vehicles with a GVWR of 10,000 pounds or less, based on the context of your letter, I am assuming that this is the case. The answer to your question is yes, if manual adjustment is the published procedure recommended by the vehicle manufacturer.
Standard 105 currently provides that where automatic brake adjusters have been locked out during testing, the brakes may be manually adjusted following the initial burnish and each subsequent reburnish. Where the automatic adjusters have not been locked out, the Standard requires that the brakes be adjusted at these points by making stops in accordance with the manufacturer's recommendations. See, S7.4.1.2, S7.6, S7.12 and S7.14.
On September 29, 1989, NHTSA published a final rule (54 FR 40080) which requires that as of September 1, 1991, for all vehicles equipped with automatic brake adjusters being tested to Standard No. 105, that the automatic adjusters be operational during the test. In addition, the rule revises the provisions in S7.4 governing brake adjustment after burnish to delete language requiring that vehicles equipped with automatic adjusters be adjusted by making stops in accordance with the manufacturer's recommendations. These provisions are revised to state that following each specified burnishing, the brakes are to be adjusted in accordance with the manufacturer's published recommendations (e.g. recommendations set forth in service literature). Thus, if the manufacturer recommends that the brakes be adjusted manually, notwithstanding the automatic adjusters, they are to be manually adjusted. Alternatively, if the manufacturer recommends that the brakes be adjusted by completing a series of specified stops, that procedure must be followed.
In conclusion, under the new provisions in Standard No. 105, brakes on a vehicle with automatic brake adjusters and a GVWR of 10,000 pounds or less should be manually adjusted at the end of the initial and subsequent burnishes if the manufacturer's published recommendations call for manual adjustment.
I hope you find this information helpful. If you have further questions, please do not hesitate to contact David Greenburg of my staff, at (202) 366-2992.
Sincerely,
Paul Jackson Rice Chief Counsel
/ref: 105 d:ll/7/90