Division 2.3 Measurement method

The reference laboratory shall measure each alignment tyre four times and retain the three last results for further analysis, in accordance with paragraph 4 of Annex 6 to UNECE Regulation No 117 and under the conditions set out in paragraph 3 of Annex 6 to UNECE Regulation No 117.

The candidate laboratory shall measure each alignment tyre (n + 1) times, with n being specified in Section 5 of this Annex and retain the n last results for further analysis, in accordance with paragraph 4 of Annex 6 to UNECE Regulation No 117 and applying the conditions set out in paragraph 3 of Annex 6 to UNECE Regulation No 117.

Each time an alignment tyre is measured, the tyre/wheel assembly shall be removed from the machine and the entire test procedure referred to in paragraph 4 of Annex 6 to UNECE Regulation No 117 shall be followed again from the start.

The candidate or reference laboratory shall calculate:

1. (a)

   the measured value of each alignment tyre for each measurement as specified in paragraphs 6.2 and 6.3 of Annex 6 to UNECE Regulation No 117 (i.e. corrected for a temperature of 25 °C and a drum diameter of 2 m);

2. (b)

   the mean value of the three last measured values of each alignment tyre (in the case of reference laboratories) or the mean value of the n last measured values of each alignment tyre (in the case of candidate laboratories); and

3. (c)

   the standard deviation (σ_m ) as follows:

   

   

   where:

   i

4. is the counter from 1 to p for the alignment tyres;

j

5. is the counter from 2 to n + 1 for the n last repetitions of each measurement of a given alignment tyre;

n + 1

6. is the number of repetitions of tyre measurements (n + 1 = 4 for reference laboratories and n + 1 ≥ 4 for candidate laboratories);

p

7. is the number of alignment tyres (p ≥ 5).