ISO 4138:2021 pdf download – Passenger cars — Steady-state circular driving behaviour — Open-loop test methods.
8 Test procedure 8.1 Warm-up The warm-up shall be carried out in accordance with ISO 15037-1:2019, 7.1. 8.2 Initial driving condition The conditions shall be in accordance with ISO 15037-1:2019, 7.2.1 and 7.2.3, and with 8.3 to 8.6 as follows, according to which method and variation is used. 8.3 General test description All necessary variables shall be recorded throughout the manoeuvre. Data shall be taken for both left and right turns. A minimum of three repetitions is recommended. For tests utilizing discrete increments of speed, radius or steering-wheel angle, all of the test data may be taken in one turning direction followed by all the data in the other turning direction, as experience has shown that this minimizes data scatter. However, to obtain more even tyre wear and reduced tyre heating, data may be taken in alternating turning directions at each test speed/radius/steering-wheel angle. The method chosen shall be noted on the test report, in the section on test-method-specific data for test conditions (see ISO 15037-1:2019, Annex B). At a minimum, data shall be taken at increments of lateral acceleration no larger than 0,5 m/s 2 . Annex C provides general information for the test methods. NOTE Where data vary rapidly with changes in lateral acceleration, it can be useful to decrease the speed/ radius/steering-wheel angle increments. The test should be repeated several times so that the results can be examined for repeatability and averaged. Caution should be exercised during testing so that tyre heating is minimized as much as possible. Tyre heating is a particular concern for test methods using continuous speed increase, with attendant long periods of data acquisition, and for all test methods at high levels of lateral acceleration. The tyres should be cooled to normal operating temperatures between test runs.
8.4 Method 1 — Constant radius 8.4.1 Description This test method requires driving the test vehicle at several speeds over a circular path of known radius. The standard radius of the path shall be 100 m, but larger and smaller radii may be used, with 40 m as the recommended lower value and 30 m as the minimum.