[F1ANNEX IVa U.K. Laboratory alignment procedure for the measurement of rolling resistance

Textual Amendments

2. GENERAL PROVISIONS U.K.

2.1. Principle U.K.

The measured Rolling Resistance Coefficient ( RRC m ) in a reference laboratory ( l ) shall be aligned to the assigned values of the network of reference laboratories.

The RRC m in a candidate laboratory ( c ) shall be aligned through one reference laboratory of the network of its choice.

2.2. Tyre selection requirements U.K.

A set of five or more alignment tyres shall be selected for the alignment procedure in compliance with the criteria below. One set shall be selected for C1 and C2 tyres together, and one set for C3 tyres.

(a)

The set of alignment tyres shall be selected so as to cover the range of different RRCs of C1 and C2 tyres together, or of C3 tyres. In any event, the difference between the highest RRC m of the tyre set, and the lowest RRC m of the tyre set shall be at least equal to:

(i)

3 kg/t for C1 and C2 tyres; and

(ii)

2 kg/t for C3 tyres.

(b)

The RRC m in the candidate or reference laboratories ( c or l) based on declared RRC values of each alignment tyre of the set shall be spaced out as follows and distributed uniformly:

(i)

1,0 +/– 0,5 kg/t for C1 and C2 tyres; and

(ii)

1,0 +/– 0,5 kg/t for C3 tyres.

(c)

The selected tyre section width of each alignment tyre shall be:

(i)

≤ 245 mm for machines measuring C1 and C2 tyres; and

(ii)

≤ 385 mm for machines measuring C3 tyres.

(d)

The selected tyre outer diameter of each alignment tyre shall be:

(i)

between 510 to 800 mm for machines measuring C1 and C2 tyres; and

(ii)

between 771 to 1 143  mm for machines measuring C3 tyres.

(e)

Load index values shall adequately cover the range of the tyres to be tested, ensuring that the rolling resistance force (RRF) values also cover the range of the tyres to be tested.

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

(a)

it shows a condition which makes it unusable for further tests; and/or

(b)

there are deviations of RRC m greater than 1,5 per cent 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 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:

(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);

(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

(c)

the standard deviation (σ m ) as follows:

where:

i

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

j

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

n

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

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 2 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 3 decimal places.

  • All RRC values will be displayed to 2 decimal places.

  • All alignment coefficients (A1 l , B1 l , A2 c and B2 c ) shall be rounded and displayed to 4 decimal places.]