Interpretation ID: 6953
Performance Friction Corp.
83 Carbon Metallic Highway
P.O. Box 819
Clover, S.C. 29710-0819
Dear Mr. Salton:
This responds to your request for an interpretation of Federal Motor Vehicle Safety Standard No. 105, Hydraulic Brake Systems (49 CFR 571.105). You stated that you are unclear about the pedal force requirements during the first fade and recovery test baseline check stops, and that an interpretation would make it clear exactly what calculation of pedal effort is used to verify compliance during the fade and recovery check stops. You also asked what values of pedal effort would be "considered non-compliance," i.e., whether peak, average or sustained control force must be within the specified limits under section S5.1.4.1. You indicated in a telephone conversation with Edward Glancy of my staff that you are primarily interested in the requirements for vehicles with a GVWR less than 10,000 pounds. Your questions are addressed below.
By way of background information, the National Highway Traffic Safety Administration does not provide approvals of motor vehicles or motor vehicle equipment. Under the National Traffic and Motor Vehicle Safety Act, it is the responsibility of the manufacturer to ensure that its vehicles or equipment comply with applicable standards. A manufacturer then certifies that its vehicles or equipment comply with the applicable standards.
Standard No. 105's fade and recovery requirements are set forth in S5.1.4. These requirements must be met under the conditions prescribed in S6, when tested according to the procedures set forth in S7. See S5.1.
The standard specifies two fade and recovery tests, each of which consists of three parts: (1) baseline check stops or snubs, (2) fade stops or snubs (the heating cycle), and (3) recovery stops or snubs. The pedal force requirements for the baseline check stops or snubs are set forth in S5.1.4.1, which reads as follows: The control force used for the baseline check stops or snubs shall be not less than 10 pounds, nor more than 60 pounds, except that the control force for a vehicle with a GVWR of 10,000 pounds or more may be between 10 pounds and 90 pounds.
S5.1.4.1 must be read in conjunction with S7.11.1, which sets forth the procedure for the baseline check stops or snubs. S7.11.1.1 provides the following procedure for vehicles with a GVWR of 10,000 pounds or less:
Make three stops from 30 mph at 10 fpsps for each stop. Control readings may be terminated when vehicle speed falls to 5 mph. Average the maximum brake control force required for the three stops.
The baseline check stops or snubs are thus made at a constant deceleration (10 fpsps), with the control force varying as necessary to maintain that constant deceleration. Under S5.1.4.1, the control force is required to stay within a prescribed range (10 pounds to 60 pounds for vehicles with a GVWR less than 10,000 pounds) throughout the entire stop or snub (from the time in which application is started until the vehicle speed falls to 5 mph, other than the initial momentary period it takes to go from 0 to 10 pounds). Thus, compliance with S5.l.4.1 is not determined based on peak, average or sustained control force. Instead, for a vehicle to comply with this test, the control force must never fall below 10 pounds or be above 60 pounds during any part of the test (for the period described above).
Your other question concerned how calculation of pedal effort during the baseline check stops or snubs is used to verify compliance during the fade and recovery check stops. As indicated above, S7.11.1.1 specifies that an average is taken of the maximum control force for the three stops. The term "maximum" refers to the peak control force for each of the stops. I note that this average is not related to whether the vehicle complies with S5.1.4.1. Instead, as discussed below, this average establishes a baseline control force, which is used to derive certain of the control force limits for the recovery stops.
The requirements for the recovery stops are set forth in S5.1.4.3, which reads as follows:
Each vehicle with a GVWR of 10,000 pounds or less shall be capable or making five recovery stops from 30 mph at 10 fpsps for each stop, with a control force application that falls within the following maximum and minimum limits: (1) A maximum for the first four recovery stops of 150 pounds, and for the fifth stop, of 20 pounds more than the average control force for the baseline check; and
(2) A minimum of--
(A) The average control force for the baseline check minus 10 pounds, or
(B) The average control force for the baseline check times 0.60, whichever is lower (but in no case lower than 5 pounds). . . .
Thus, the minimum and (for one stop) the maximum control force limits for the recovery stops are calculated using the average control force for the baseline check stops or snubs. This average control force is the one calculated under S7.11.1.1 using the maximum control force of each of the baseline check stops or snubs.
I hope this information is helpful. If you have any further questions about NHTSA's safety standards, please feel free to contact Marvin Shaw of my staff at this address or by telephone at (202) 366-2992.
Sincerely,
Paul Jackson Rice Chief Counsel
Ref:105 d:4/14/92