Candidate laboratories shall repeat the alignment procedure at least once every second year for every machine and always after any significant machine change or any drift in machine control tyre monitoring data.
A common set of five different tyres that have been selected in accordance with Section 2.2 shall be measured in accordance with Section 2.3 first by the candidate laboratory and then by one reference laboratory. More than five alignment tyres may be tested at the request of the candidate laboratory.
The candidate laboratory shall provide the alignment tyre set to the selected reference laboratory.
The candidate laboratory (c) shall comply with the specifications of Annex 6 to UNECE Regulation No 117 and preferably have standard deviations (σm ) as follows:
not greater than 0,075 N/kN for C1 tyres and C2 tyres; and
not greater than 0,06 N/kN for C3 tyres.
If the standard deviation (σm ) of the candidate laboratory is higher than those values after four measurements, the last three being used for the computations, then the number n + 1 of measurement repetitions shall be increased as follows for the entire batch:
n + 1 = 1 + (σm /γ)2, rounded up to the nearest higher integer value
where:
γ = 0,043 N/kN for C1 tyres and C2 tyres;
γ = 0,035 N/kN for C3 tyres.