Regulation No. 117 (Tyres rolling noise and wet grip adhesion) Proposal for amendments to ECE/TRANS/WP.29/GRB/2010/3

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1 Transmtted by the expert from France Informal Document No. GRB (67 th GRB, February 2010, agenda tem 7) Regulaton No. 117 (Tyres rollng nose and wet grp adheson) Proposal for amendments to ECE/TRANS/WP.29/GRB/2010/3 Ths document supersedes nformal document No GRRF transmtted by France and presented at GRRF of February The text reproduced below was prepared by the expert from France to ntroduce some correctons n the document ECE/TRANS/WP.29/GRB/2010/3 and to adjust some values remaned between brackets. An explanaton of the choce of these new values s provded n the appendx. It also ncludes addtonal results from expermental values to llustrate the nfluence of the tyre type number to be used for the algnment process. The modfcatons to the document ECE/TRANS/WP.29/GRB/2010/3 are marked n bold or strkethrough characters and supersedes GRRF A. PROPOSAL Annex 6 paragraph 2.2 (a), 3.4 table 2 note (a) and annex 6 appendx 1 paragraph 2.1: Replace ISO :[2009] by ISO :2007 Annex 6 paragraph 3.2 table 1: correct to read Tyre Type C1 C2 and C3 C3 Class Load Index All LI=121 and below LI 121 LI=122 and above LI > 121 Speed Symbol All All J 100 km/h and lower or tyres not marked K 110 km/h and hgher wth speed symbol Speed Annex 6 paragraph 4.4 table 3: correct to read Tyre Type Class Class C1 Class C2 and C3 LI 121 Class C3 LI > 121 Nomnal Rm Dameter All All < Warm up duraton 30 mn. 50 mn mn. 180 mn.

2 page 2 Annex 6 paragraph 6.5 correct the formula n = ( σ m,i / x)² n = (σ m, / x)² Annex 8: Ttle: Annex 8 [(nformatve)] amend to read Annex 8 (nformatve) Annex 8 paragraph 1: correct to read.1. Ths clause descrbes the procedure to be followed to perform nter-laboratory comparson. It can be used for determnaton of assgned values (see paragraph below) for a set of reference tyres. Annex 8 Add new paragraphs 2, 3 and 4 2. Any addtonal techncal servce wshng to refer to assgned values shall perform the same set of measurements than those partcpatng to the nter laboratory comparson. 3. Any new measurements wll not affect the current assgned values 4 The nter laboratory shall be repeated perodcally (e.g. at every two years). Annex 8 1.2, Annex 9 1.1, 2.2, 4.1: Delete the word predetermned Annex 9: Ttle: Annex 9 [(nformatve)] amend to read Annex 9 (nformatve) Annex 9 paragraph 1.1: correct to read: 1.1. Algnment tyres Set of [1-5] [at least 5] predetermned tyres measured by both the canddate and Techncal Servce machnes to perform machne algnment. Annex 9 paragraph 2.2: correct to read: 2.2. The machne algnment procedure requres [1-5] [at least 5] predetermned algnment tyres used by the canddate laboratory operatng the machne. These tyres are used to algn canddate machne(s) by comparng the measured Cr results to the ones obtaned by a Techncal Servce elgble n the nter-laboratory comparson. An algnment formula s then establshed and shall be used to translate the results obtaned on the canddate machne nto algned results.

3 page 3 Annexe 9 paragraph 4.1: correct to read: 4.1. The predetermned algnment tyres used to conduct the algnment procedure shall be dentfed to cover the needed usage range n terms of load ndex, Cr and Fr Cr, dmensons, Fr and load ndex as follows: (a) Cr values shall have a mnmum range gap between two algnment tyres of: [3 N/kN] [1.5 +/- 0.5 N/kN] for Class C1 and C2 tyres, and [2 N/kN] [1.0 +/- 0.5 N/kN] for Class C3 tyres. (b), (c), (d) are nchanged The number of algnment tyres shall be equal to [1-5] [at least 5],.e. there shall be: [1-5] [at least 5] algnment tyres for Class C1 and C2 tyres, and [1-5] [at least 5] algnment tyres for Class C3 tyres. Annex 9 paragraph 5.1, 5.2, 5.3 replace paragraph 4 by paragraph 4 of annex 6 and paragraph 3 by paragraph 3 of annex 6 Annex 9 paragraph 5.3 (a) and (b), correct to read: (a) (b) not greater than [0.05] [0,075 N/kN] for Class C1 and C2 tyres, and not greater than [0.05] [0,06 N/kN] for Class C3 tyres. B. JUSTIFICATIONS Annex 6: - The current standard ISO s dated 2007 and not It exst a new draft for ths standard but t s not yet voted. - Table 1and Table 3: -The replacement of Tyre Type by Tyre Class s n accordance wth the defnton (see 2.4). -C3 has been added n the second column because some of current tyres of ths class have a load ndex <= LI = 121 and below and LI=122 and above replaced respectvely by LI<=121 and LI>121 s to be n coherence between the dfferent tables. -Table 3: 150 mn nstead 550 mn to be n coherence wth ISO : Index n the formula has to be n small letter and not n captal letter Annex 8: - Ttle: Ths annex shall be nformatve.

4 page 4-1: Error n the number of paragraph referred n the parenthess. - 2: Ths added paragraph s needed to nclude the case where a techncal servce wants to perform tests after the nter laboratory comparson s fnshed. It has to use the same set of samples n order to be compared wth the other laboratores. - 3: Ths paragraph means that the assgned values are not modfed f a techncal servce performs tests after the nter laboratory comparson. Annex 8 1.2, Annex 9 1.1, 2.2, 4.1: The word predetermned can be deleted because the manner to choose the tyres are well defned trough the range to be covered and the dstrbuton of the tyres wthn the range (see the new paragraph 4.1). Annex 9 - Ttle ths annex shall be nformatve Annex 9 1.1, 2.2 and 4.1: Durng the dfferent meetngs of the STD nformal group no consensus was obtaned among the partcpants on the number of tyres to be used for the algnment process. For that reason, we try to show theoretcally n the appendx of ths nformal document why a number of at least 5 tyres s needed to have a good precson n the algnment process. Annex (a): - Takng nto account both the number of tyres used.n the algnment process (at least 5) and the total usage range of the coeffcents (e.g. 5.5 to 12 for C1 Tyre Class), we need to lmt the gap between each algnment tyre n order to have a homogeneous dstrbuton. Annex 9 paragraphs 5.1, 5.2, 5.3: The number of the annex has been added. Annex 9 paragraph 5.3 (a) and (b): The values nto brackets have been changed to be n coherence wth the other parts of the document

5 page 5 Appendx Accordng to the 5.4 of the annex 9, the algnment process conssts to establsh a lnear regresson between two varables based on a regresson model smlar to: y = a + + ε from whch we are able to estmate the parameters a and b by â and bx bˆ. The standard devaton for a new predcted value y ˆ ˆ ˆ 0 = a + bx0 s gven by the formula: x x t ) 2 1 ( 0 ) σ 1+ + (1) n 2 ( x x) ± n σˆ beng an estmaton of the repeatablty standard devaton such as defned n 5.3, the above quantty can be only reduced n ncreasng: - n and 2 - the sum of square ( x x. n ) n represents n our case the number of algnment tyres and the sum of square represents the varaton range of the data x that s to say the needed usage range. By ncreasng n both quantty n 1 and t value comng from the Student s dstrbuton test, accordng to the table below, are decreasng. n value Number of degrees of freedom t such P( Tn 2 > t) = 5% ,2 Consderng that the mpact of t s mportant n the relaton (1) and lookng at ts varaton versus the n values (see table above) there s a bg nterest to have the most mportant number of tyre types samples n to reduce the standard devaton of the predcted values

6 page 6 An example based on expermental measurement values obtaned for 11dfferent tyre types n sx dfferent labs, s gven hereafter, at fgure 1. Two measurements were performed for each tyre n each lab. RR measured coeffcents are plotted versus the calculated average of the RR obtaned for the sx labs, for each tyres type. Fgure 1 RR Coeffcent Scatter Plot 13, ,5 y = 1,03x - 0,1306 R 2 = 0, RR value (N/kN) 11, ,5 10 9,5 Lab # 1 Lab # 2 Lab # 3 Lab # 4 Lab # 5 Lab # 6 Lnear regresson 9 8,5 8 7,5 7,50 8,00 8,50 9,00 9,50 10,00 10,50 11,00 11,50 12,00 12,50 13,00 13,50 14,00 14,50 15,00 15,50 Tyre Type Seral Mean Value (N/kN) The evoluton of standard devaton (SD) for the predcted value versus tyre types number s plotted n fgure 2. The standard devaton accordng to paragraph 5.3 of annex 9 s fxed to 0,075 N/kN. A range of tyre type n between : 8,30 and 10,21 for 3 tyre types; 8,30 and 10,72 for 5 tyre types; 8,30 and 11,47 for 7 tyre types; 8,30 and 11,59 for 9 tyre types were consdered. 1) predcted value s performed from a gven value x0 =12N/kN located out of the range; 2) predcted value s performed from a gven value x0 equal to the mean of the x 3) predcted value s performed from a gven value x0 =9N/kN located wthn range

7 page 7 Conclusons: These results confrm that the SD for predcted values decreases wth the number of tyre types, whatever the case. It also confrms the need to measure at least more than fve tyre types to obtan a good SD for predcted value. The worst case, n ths example, s obtaned when the SD for predcted value s evaluated, for a gven value x0 located out of the range, especally for a reduced number of tyres. The SD for predcted value evaluated for a gven value x0, equal to the mean of the x or located wthn the range, s lower. Therefore, more than 5 tyre types are stll necessary. Fgure 2 Evoluton of SD for predcted value, versus tyre types number 2,500 SD for predcted value (N/kN) 2,000 1,500 1,000 0,500 value x0 out of the range x0 equal to the mean of the x x0 located located wthn the range 0, Number of Tyre Types

8 page 8 Table 1: calculaton x Average 9,41 9,91 10,25 10,56 Resdual STD 0,075 0,075 0,075 0,075 t(n-2) 12,706 3,182 2,571 2,447 n ,21 10,72 11,47 11,47 9,73 10,59 10,72 10,72 8,30 10,21 10,75 10,75 9,73 10,21 11,71 RR 8,30 10,59 11,59 9,73 10,21 8,30 10,59 9,73 8,30 STD predcted value 2,07 0,37 0,25 0,21 x0 average average average average Average 9,41 9,91 10,25 10,56 Resdual STD 0,075 0,075 0,075 0,075 t(n-2) 12,706 3,182 2,571 2,447 n ,21 10,72 11,47 11,47 9,73 10,21 10,72 10,72 8,30 10,59 10,75 10,75 9,73 10,21 11,71 8,30 10,59 11,59 9,73 10,21 8,30 10,59 9,73 8,30 STD predcted value 1,10 0,26 0,21 0,19 x Average 10,13 10,18 10,31 10,58 Resdual STD 0,075 0,075 0,075 0,075 t(n-2) 12,706 3,182 2,571 2,447 n ,89 11,89 11,89 11,89 10,21 10,75 10,75 11,59 8,30 10,21 10,72 11,47 9,73 10,59 10,75 RR 8,30 10,21 10,72 9,73 10,59 8,30 10,21 9,73 8,30 STD predcted value 1,18 0,28 0,23 0,21