Interpretation ID: nht92-2.49

DATE: 11/03/92

FROM: LEO WENSTRUP -- MANAGER - TECHNICAL SERVICES, EATON CORPORATION AXLE & BRAKE DIVISION

TO: OFFICE OF CHIEF COUNSEL, NHTSA

COPYEE: J. DOAN; B. PICKORNIK; B. WALTER

TITLE: BRAKE DYNAMOMETER CERTIFICATION TESTING

ATTACHMT: ATTACHED TO LETTER DATED 12-29-92 FROM PAUL J. RICE TO LEO WENSTRUP (A40; STD, 121)

TEXT: To Whom It may Concern,

Our company has been requested by a customer who uses our brake products in a City refuse fleet to pursue alternative lining materials. The reason for their request is the current lining formulation is very aggressive and prone to noise. This lining was chosen based on standard dynamometer certification testing as required by Section S5.4 and S6.2 of FMVSS-121 to a GAWR and rolling radius in excess of this fleets vehicle specifications.

It was decided to conduct certification testing to the exact vehicle specifications to optimize the brake performance for this customer. In reviewing the vehicles specifications, it was noted the maximum vehicle speed is governed to 45 MPH. This is below the initial speed of the fade portion of the FMVSS-121 dynamometer certification protocol in section S5.4.2.

At what speed should the fade portion of this certification be conducted in light of the fact the vehicle is incapable of meeting the test conditions?

I thank you in advance for your office's review of this enquiry and a timely response.