Document ID: chunk:federal_register_of_legislation:F2021C00477:body:0:p44
Version: federal_register_of_legislation:F2021C00477
Segment Type: other
Provision Reference: 
Character Range: 116655–119225

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 must 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 and 100°C average on the hottest axle.
(b) Test speeds: 100 km/h and 50 km/h.
(c) Pedal force: Pedal force is increased at a linear rate between 100 and 150 N/sec for the 100 km/h test speed, or between 100 and 200 N/sec for the 50 km/h test speed, until the first axle locks or until a pedal force of 1 kN is reached, whichever occurs first.
(d) Brake cooling: Between brake applications, the vehicle is driven at speeds up to 100 km/h until the initial brake temperature specified in paragraph 3.(a) above is reached.
(e) Number of runs: With the vehicle unladen, run five stops from a speed of 100 km/h and five stops from a speed of 50 km/h, while alternating between the two test speeds after each stop. With the vehicle laden, repeat the five stops at each test speed while alternating between the two test speeds.
(f) Test surface: This test is conducted on a road test surface affording good