Division 2.3 Measurement methodF1

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 of UNECE Regulation No 117 and its subsequent amendments and applying the conditions set out in paragraph 3 of Annex 6 of UNECE Regulation No 117 and its subsequent amendments.

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

Each time an alignment tyre is measured, the tyre/wheel assembly shall be removed from the machine and the entire test procedure specified in paragraph 4 of Annex 6 of UNECE Regulation No 117 and its subsequent amendments 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 Annex 6, paragraphs 6.2 and 6.3, of UNECE Regulation No 117 and its subsequent amendments (i.e. corrected for a temperature of 25 °C and a drum diameter of 2 m);

2. (b)

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

3. (c)

   the standard deviation (σ _m ) as follows:

   ${\sigma }_m=\sqrt{\frac{1}{p}\times \sum _{i=1}^p{\sigma }_2^{\mathrm{m,i}}}$

   ${\sigma }_{\mathrm{m,i}}=\sqrt{\frac{1}{n-2}\times \sum _{j=2}^n{\left({\mathrm{Cr}}_{\mathrm{i,j}}-\frac{1}{n-1}\times \sum _{j=2}^n{\mathrm{Cr}}_{\mathrm{i,j}}\right)}^2}$

   where:

   i

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

j

5. is the counter from 2 to n for the number of repetitions of each measurement for a given alignment tyre

n

6. is the number of repetitions of tyre measurements (n ≥4)

p

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