Regulation (EU) 2020/740 of the European Parliament and of the CouncilShow full title

2. General provisions U.K.

2.1. Principle U.K.

The measured (m) rolling resistance coefficient obtained in a reference laboratory (l), (RRC_m,l ), shall be aligned to the assigned values of the network of reference laboratories.

The measured (m) rolling resistance coefficient obtained by a machine in a candidate laboratory (c), (RRC_m,c ), shall be aligned through one reference laboratory of the network of its choice.

2.2. Tyre selection requirements U.K.

Alignment tyre sets shall be selected for the laboratory alignment procedure in accordance with the following criteria. One alignment tyre set shall be selected for C1 tyres and C2 tyres together, and one set for C3 tyres:

(a)

the alignment tyre set shall be selected so as to cover the range of different RRCs of C1 tyres and C2 tyres together, or of C3 tyres; in any event, the difference between the highest RRC_m of the alignment tyre set, and the lowest RRC_m of the alignment tyre set shall be, before and after alignment, at least equal to:

(i)

3 N/kN for C1 tyres and C2 tyres; and

(ii)

2 N/kN for C3 tyres;

(b)

the RRC_m in the candidate or reference laboratories (RRC_m,c or RRC_m,l ) based on declared RRC values of each alignment tyre of the alignment tyre set shall be distributed evenly;

(c)

load index values shall adequately cover the range of the tyres to be tested, ensuring that the rolling resistance values also cover the range of the tyres to be tested.

Each alignment tyre shall be checked prior to use and shall be replaced when:

(a)

the alignment tyre shows a condition which makes it unusable for further tests; or

(b)

there are deviations of RRC_m,c or RRC_m,l greater than 1,5 % relative to earlier measurements after correction for any machine drift.

2.3. Measurement method U.K.

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:

(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);

(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

(c)

the standard deviation (σ_m ) as follows:

where:

i

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

j

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

n + 1

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

p

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

2.4. Data formats to be used for the computations and results U.K.

The measured RRC values corrected from drum diameter and temperature shall be rounded to two decimal places.

Then the computations shall be made with all digits: there shall be no further rounding except on the final alignment equations.

All standard deviation values shall be displayed to three decimal places.

All RRC values will be displayed to two decimal places.

All alignment coefficients (A1 _l , B1 _l , A2 _c and B2 _c ) shall be rounded and displayed to four decimal places.