Document ID: chunk:federal_register_of_legislation:F2021C01192:body:0:p40
Version: federal_register_of_legislation:F2021C01192
Segment Type: other
Provision Reference: 
Character Range: 107199–109842

linear rate such that the first axle lockup occurs no less than one-half (0.5) second and no more than one and one-half (1.5) seconds after the initial application of the pedal.
(iii) The pedal is released when the second axle locks, or when the pedal force reaches l kN, or 0.1 seconds after the first lockup, whichever occurs first.
(d) Wheel lockup: Only wheel lockups above a vehicle speed of 15 km/h are considered.
(e) Test surface: This test is conducted on road test surfaces on which wheel lockup occurs at braking rates between 0.15 and 0.8.
(f) Data to be recorded: The following information shall be automatically recorded in phase continuously throughout each test run such that values of the variables can be cross referenced in real time:
(i) Vehicle speed;
(ii) Instantaneous vehicle braking rate (e.g. by differentiation of vehicle speed);
(iii) Brake pedal force (or hydraulic line pressure);
(iv) Angular velocity at each wheel.
(g) Each test run shall be repeated once to confirm the wheel lockup sequence: if one of these two results indicates a failure to comply, then a third test run under the same conditions will be decisive.
4. Performance requirements
(a) Both rear wheels shall not reach a locked condition prior to both front wheels being locked - at vehicle braking rates between 0.15 and 0.8.
(b) If, when tested to the procedure specified above, and at vehicle braking rates between 0.15 and 0.8 the vehicle meets one of the following criteria, then it passes this wheel lockup sequence requirement:
(i) No wheels lock;
(ii) Both wheels on the front axle and one or no wheels on the rear axle lock;
(iii) Both axles simultaneously lock.
(c) If wheel lockup commences at a braking rate less than 0.15 and more than 0.8 then the test is invalid and should be repeated on a different road surface.
(d) If, either laden or unladen, at a braking rate between 0.15 and 0.8 both wheels on the rear axle and one or no wheels on the front axle lock, then it fails the wheel lockup sequence test. In this latter case, the vehicle shall be submitted to the 'torque wheels' test procedure to determine the objective brake factors for calculation of the adhesion utilization curves.
Annex 5 - Appendix 2
  Torque wheel test procedure
1. General information
 The purpose of this test is to measure the brake factors and thus determine the adhesion utilization of the front and rear axles over a range of braking rates between 0.15 and 0.8.
2.  Vehicle conditions
(a) Vehicle load: Laden and unladen
(b) Transmission position: Engine disconnected
3. Test conditions and procedures
(a) Initial brake temperature: Between 65 °C