Rolling Noise Emission of Tyres – A Market Survey

Hans G. Jonasson

Energy Technology

SP Report 2007:70

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Abstract Rolling Noise Emission of Tyres – A Market Survey 21 C1 tyres, 20 C2 tyres and 9 C3 tyres for passenger cars, vans and trucks respectively have been tested according to the European tyre noise directive. In addition the tyres were tested on two typical Swedish roads. Two different ISO tracks were used and the difference between them was estimated to be about 2 dB. All tyres, C1, C2 and C3, complied with the requirements laid down in the current tyre directive. However, the marginal was not large. At most 50% of the C1 tyres have the potential of meeting the proposed 2012 requirements if tested on an optimum ISO test track. None of the tyres met these proposed values on the ISO track used. 6(20) of the C2 tyres met the 2012 limit values proposed by the Commission. As to C3 tyres 2 (9) tyres met the 2012 proposal. The difference between normal roads and ISO tracks is according to expectations, that is quite large. The difference is about 2 dB greater for C2 tyres than for C3 tyres. Also, as expected, the relative ranking of the different tyres are different between an ISO track and a normal road. Normally the difference is manageable but there are cases when it is quite significant. Key words: tyre, tyre/road, noise, measurement SP Sveriges Tekniska Forskningsinstitut SP Technical Research Institute of Sweden SP Report: 2007:70 ISBN 978-91-85829-02-6 ISSN 0284-5172 Borås 2007-11-06

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Contents Abstract 3

Contents 4

Preface 5

1 Introduction 7 1.1 Background 7 1.2 Practical problems during the tests 7

2 Some facts on tyres 9 2.1 General 9 2.2 Marking on tyres 9 2.3 Tyre noise directive 9 2.4 Public consultation document from the Commission 10

3 Practical arrangements 12 3.1 Tyre selection 12 3.2 Description of tyres tested 13 3.2.1 C1 tyres 13 3.2.2 C2 tyres 15 3.2.3 C3 tyres 17 3.3 Vehicles used for the tests 18 3.3.1 Passenger cars 18 3.3.2 Vans, light trucks 19 3.3.3 Heavy truck 20

4 Description of the measurement sites 22 4.1 Volvo Hällered 22 4.2 Volvo Torslanda 23 4.3 Comparison between the Hällered and the Torslanda track 23 4.4 Nävraspång 24 4.5 Sörredsvägen 25

5 Description of measurements 26 5.1 Principle 26 5.2 Test procedure on the ISO tracks. 26 5.3 Test procedure on the roads. 27

6 Results 28 6.1 General 28 6.2 C1 tyres 28 6.3 C2 tyres 31 6.4 C3 tyres 35

7 Conclusions 38

8 References 39

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Preface This project has been an assignment from the Swedish Road Administration represented by Sören Hedberg. The project would not have been possible without the kind support from Volvo Truck Corporation and Volvo Car Corporation which both gave SP access to their ISO test tracks at Hällered and Torslanda respectively. Volvo Car Corporation also generously offered cars, tyres and a mechanic at SP:s disposal. C3 tyres and C2 tyres were leased from Vianor and Arnes Gummiverkstad respectively, both in Borås. Toveks Bil and Borås Bil generously put one van each at SP:s disposal. At Hällered Geir Andresen and Göran Pettersson offered excellent support as did Roger Andersson at Torslanda. From SP Xuetao Zhang carried out the test track measurements and Joachim Stadig, supported by Florian Mack, carried out the road measurements. Mohammad Jalalian, Mikael Karlsson and Sune Claesson were drivers. The support of the above mentioned organizations and individuals is gratefully acknowledged. Hans Jonasson

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1 Introduction 1.1 Background About 25% of the population within the European Union is disturbed by traffic noise, predominantly road traffic noise. Road traffic noise is mostly generated by the tyre/road interaction although also engine noise may be important during acceleration and at speeds below 50 km/h. To erect a platform to deal with this problem the European directive 2001/43/EC on tyre/road noise was adopted in 2001 as an amendment to directive 92/23/EEC, [1], dealing with the safety of tyres. According to this directive all tyres first put on the market after 4 August 2003 shall be type approved according to the requirements given. After 1 October 2009 to 1 October 2011, depending on tyre type, all tyres, with few exceptions, put on the market shall be type approved with respect to noise. The Commission has the task to prepare a step 2 for further reduction in permissible levels. It has been recognized that the current values in the directive will not contribute to a significantly quieter road traffic noise environment. As part of this process the FEHRL report, [4], has been elaborated. In this report background material is presented and discussed and new limit values are proposed. Based on this report the Commission has made a proposal, [6], for new limit values to become effective in 2012. This proposal has been subject to public consultation until 18 October 2007. Sweden has special interests in this field, partly for having promoting the first tyre/road noise directive and partly for having conditions deviating from many other countries in Europe. In Sweden studded tyres are extensively used during winter time and because of the increased wear of the roads Swedish roads have on average greater chipping size than what is common elsewhere. Swedish truck and trailer combinations are also, on average, longer with more axles compared to continental Europe. The most typical roads are DAC or SMA 0/16. These roads are quite noisy and they are also very different from the specified test track according to ISO 10844, [3], specified in the tyre/noise directive. Another difference is that winter tyres are mandatory in Sweden during 1 Dec – 31 March in case of winter conditions on the roads. The aim of this project is to supply the Swedish Road Administration with some up-to-date data on tyre/road noise conditions in Sweden. 1.2 Practical problems during the tests In Sweden the only test tracks according to ISO 10844 available are those of the car manufacturers. These tracks are very busy and there are severe restrictions on external organizations to get access to them. Nevertheless SP managed to make arrangements with Volvo Truck Corporation and Volvo Car Corporation to borrow the tracks at Hällered and Torslanda respectively. However , the time was limited to one week only at each site and this, together with the rainiest summer for many years, made it quite difficult to manage the test programme. At Hällered we planned to test 20 C2 and 10 C3 tyres but due to long rain periods we had to cancel the last C3 measurement. Two whole days were lost because of rain and also the other days were affected by rain disturbances. At Torslanda we were fortunate to start with two very nice (and long) days during which we managed to test 22 different tyres but the rest of the week was spoiled because of rain.

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Because of the short time periods available the logistics also got complicated. It was not possible to use the same vehicle for all tyres of the same category except for the C3 tyres. We had to use 3-4 vehicles simultaneously which meant that we were up to 9 people working simultaneously with the project. Another problem was that the project didn’t start until the beginning of the holiday season. Thus we had to get access to the tyres during a period when hardly anybody worked in Sweden. This put some restraints on our choice of tyres. We more or less had to test what we could get. Because of the limited time available we also had to simplify the tests on ordinary roads. We could not afford to drive too far to get a suitable road with our preferred surface and nice measurement conditions nor could we afford to make a complete test according to the directive. We had to select a site very close to the ISO track and limit the number of coast-by measurements.

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2 Some facts on tyres 2.1 General The tyre directive, [1] uses three main categories of tyres: C1, C2 and C3 for passenger cars, vans and light trucks and heavy trucks respectively. Commercial tyres in the C2 and C3 categories are normally reinforced with more layers. Some C1 tyres may also be reinforced in which case they are marked reinforced or extra load. The tyres are intended for different maximum loads and different speeds. Usually these are denoted as special load and speed indices. The maximum load is coupled to the maximum inflated pressure. Trucks often use different tyres on different axles. The drive axle is normally equipped with tyres with better grip whereas tyres for trailers and steering axles tend to have lower rolling resistance. 2.2 Marking on tyres There are several markings on the side of a tyre carcass. The markings are on both sides of the tyre but they may be a little different from side to side. Depending on rolling direction this means that the outside sides of the tyres on a specific car may have slightly different markings. The most important markings are as follows:

• Brand and product identity, e.g. Avon Avanza; • width, aspect ratio, rim size, load and speed index, e.g. 225/65/16 W 96, which

means that the width of the tyre is 225 mm, the height of the side is 65% of 225 mm, the rim diameter is 16 inches, the load index is 96 (= 710 kg) and the speed index W (= 270 km/h), other indices can be found in [1] or [2];

• max load at max pressure, e.g. 710 kg at 275 kPa; • ECE and EEC type approval numbers, e.g. E2009606, e20003600-s; • indication M+S (mud and snow); • indication of month and year of manufacture, e.g. 4606 indicating that the tyre

was manufactured week 46 in 2006; • indication if it is reinforced (C, commercial, or extra load).

There are additional markings especially for the American market but these are not dealt with here. 2.3 Tyre noise directive The European Union directive 92/23/EEC, [1], prescribes procedures and requirements for the type approval of tyres to be used within the Community. Noise is among the properties regulated and it is dealt with in Annex V with appendix 1 and 2 and in Annex VI.

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Table 2.1 Limit values, LAFmax for category C1 according to 92/23/EEC. Limit value,

LAFmax, dB Limit value, LAFmax, dB

Limit value, LAFmax, dB

Tyre class Nominal section width mm

A B C

C1a < 145 72(*) 71(*) 70 C1b > 145 < 165 73(*) 72(*) 71 C1c >165 < 185 74(*) 73(*) 72 C1d >185 < 215 75(**) 74(**) 74 C1e > 215 76(***) 75(***) 75 (*) Limit values in column A shall apply until 30 June 2007 Limit values in column B shall apply as from 1 July 2007 (**) Limit values in column A shall apply until 30 June 2008 Limit values in column B shall apply as from 1 July 2008 (***) Limit values in column A shall apply until 30 June 2009 Limit values in column B shall apply as from 1 July 2009 The tabular values given in column B and C are indicative values only and are to be followed up by an amendment later giving definitive values. For reinforced (or Extra Load) the limit values in table 2.1 shall be increased by 1 dB and for “Special” tyres they shall be increased by 2 dB. The corresponding values for category C2 and C3 are given in table 2.2 and 2.3 respectively. Table 2.2 Limit values, LAFmax for category C2 according to 92/23/EEC Category of use Limit value, LAFmax, dB Normal 75 Snow 77 Special 78 Table 2.3 Limit values, LAFmax for category C3 according to 92/23/EEC Category of use Limit value, LAFmax, dB Normal 76 Snow 78 Special 79 2.4 Public consultation document from the

Commission Based on the FEHRL-report, [4], the European Commission proposes new limit values for tyre/road noise in a public consultation in July 2007, [6]. The FEHRL report includes proposals for both 2008 and 2012 but the proposal of the Commission is restricted to the 2012 values taken from the report. The proposed limit values are given in tables 2.4 – 2.6. In addition to the amended limit values it is also proposed to dispose of the one dB subtraction from the measured value to “take the measurement uncertainty into account”. Table 2.4 Proposed tyre noise limits(2012) for C1 tyres (rounding to nearest integer only) New tyre class

Nominal section width (mm)

Limit value, LAFmax, dB

Reduction compared with current limit value, dB

C1a_new < 185 71 2,5 – 4,5 C1b_new 185-215 72 4,5 C1c_new 215 - 245 72 5,5 C1d_new 245 - 275 73 4,5 C1e_new > 275 75 2,5

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For tyres classified in the category of use “Special” the limit values given in table 2.4 shall be increased by 1 dB. Special use tyre means a tyre intended for mixed use both on- and off-road or for other special duty and which has all of the following characteristics: tread depth ≥11 mm, void-to-fill ratio ≥ 35%, max speed rating ≤160 km/h and marking to denote mud and snow use. Table 2.5 Proposed tyre noise limits (2012) for C2 tyres (rounding to nearest integer only) Tyre class

Type Limit value, LAFmax, dB

Reduction compared with current limit value, dB

C2 Normal 71 5,5 C2 Snow (M+S) 72 6,5 C2 Special 74 5,5 Table 2.6 Proposed tyre noise limits (2012) for C3 tyres (rounding to nearest integer only) Tyre class

Type Limit value, LAFmax, dB

Relative decrease compared to current limit value

C3 Normal 71 6,5 C3 Snow (M+S) 73 6,5 C3 Special 75 5,5

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3 Practical arrangements 3.1 Tyre selection The starting point for the selection of tyres to be tested was some general guidelines from the Swedish Road Administration. In principal these guidelines requested that the tyres were manufactured not earlier than 2006 and that they were representative to the Swedish market. However, some practical considerations also influenced the choices made. One restraint was economy and the other time. As to time the project started just before the summer holidays in Sweden and we could only gain access to the ISO test tracks during this holiday time. Thus there was little time for elaborate planning or to wait for tyres. As to C3 tyres they were the most expensive to lease and one condition to be able to do so was that they should be of such brand and type that they could be sold afterwards. As super singles are rarely used in Sweden it was not possible to lease such tyres at a reasonable cost. Instead we tested two such tyres that Volvo Truck Corporation happened to have access to. However, we then had to accept that they were manufactured before 2006. All the other C3 tyres were quite new. The situation for C2 tyres was similar although the cost was significantly lower. All C2 tyres were quite new apart from a few that were already mounted on the test vehicle and which were judged to be as good as to be equivalent to new ones. C1 tyres were selected from tyres available at Volvo from different test vehicles. They were selected to be in very good condition and not older than 2006 although, due to time pressure, some exceptions were unintentionally made. The tread depth of all these tyres was measured.

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3.2 Description of tyres tested 3.2.1 C1 tyres The C1 tyres tested are listed in table 3.1. Table 3.1 C1 tyres tested Make Width Ratio Rim Load Speed Type Age Approval Approval1.Michelin Pilot Primacy Radial XSE 195 65 15 91 V 4806 E20289570 e20203504-s2.Continental 4x4 Contact Xtra load 215 65 16 102 V M+S 1007 E40236841 e40223360-S3.Pirelli standard load 235 55 17 99 H M+S 4605 E40219611 e40224426-s4.Continental 4x4 Contact 235 55 17 99 H M+S 806 e40223360-s5.Pirelli standard load 205 55 16 91 V 1707 E30253353 e40224422-s6.Continental Sport Contact 2 Xtra load 205 50 17 93 W 1707 E40219504 e40223362-s7.Pirelli standard load Winter 210 MO 205 55 16 91 H 4706 E4029673 e40224426-s8.Pirelli P7 Standard load 205 55 16 91 W 2406 E30253353 e40224422-s9.ContiWinterContact TS810 195 65 15 91 T M+S 2505 E40225019 e40227301-s10.Pirelli PZERO ROSSO extra load 215 45 18 93 W 3803 E3022243 e40224420-s11.Continental Cross Contact UHP 235 60 18 103 V 1506 E40219752 e40223345-s12.Continental Cross Contact UHP 235 60 18 103 V 1506 E40219752 e40223345-s13.Michelin 4x4 Synchrone 235 65 17 104 H M+S F23X E2028548 e20203501-s14.ContiWinterContact 4x4 235 65 17 104 H M+S 3906 E40211549 e40223997-s15.Pirelli standard load 255 50 19 103 W 806 E3022192 e40224420-s16.Michelin Xtra load 245 45 17 99 W 5106 E20205534 e20205502-s17.Pirelli PZERO Rosso Extra load (XL) 245 40 ZR18 97 Y 3506 E40211936 e40224420-s18.Continental Sport Contact 2 225 50 17 98 W 3806 E40218870 e40223362-219.Continental WinterContact TS810 XL 225 50 17 98 H M+S 4306 E40225026 e40227301-s20.Michelin exra load (XL) 225 50 17 98 W 4006 E20204555 e20205502-521.Pirelli P7 standard load 225 55 16 95 W 4806 E30251823 e40224422-s22.Michelin Pilot Sport 235 35 ZR19 87 Y 2305 E2022580 e20203508-s

All tyres were in very good condition but tyre 11 and 15 which were visibly worn but still far from being worn out. Tyre 12 was identical to tyre 11 but with 1,4 mm more tread depth. Photos of the different tyres are shown below. The number below each photo refers to the numbers in table 3.1. The mm figure is the measured tread depth.

T1 T2 7,8 mm T3 7,9 mm T4 7,4 mm

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T5 7,7 mm T6 6,7 mm T7 6,9 mm T8 7,4 mm

T9 8,4 mm T10 6,6 mm T11 4,9 mm T12 6,3 mm

T13 7,2 mm T14 7,7 mm T15 6,5 mm T16 6,1 mm

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T17 7,5 mm T18 7,6 mm T19 8,2 mm T20 6,4 mm

T21 7,3 mm T22 6,2 mm 3.2.2 C2 tyres The C2 tyres tested are listed in table 3.2. Table 3.2 C2 tyres tested. Make Width Ratio Rim Load Speed Type Age Approval Approval1.Michelin Agilis 81 225 65 16C 112 R M+S 1207 E2009606 e20003600-S2.Goodyear Cargo G26 225 65 16C 112 R 1807 E13008377 e13009260-s3.Nokian NRC-2 225 65 16C 112 R 1906 E170054101 e1700007-s4.Sava Trenta 225 65 16C 112 R 1607 E13008377 e13009233-s5.Bridgestone R630 Duravis 225 65 16C 112 R E400124946.Avon Avanza AV 9 225 65 16C 112 R 607 E110016547.Continental Vanco-8 205 70 16 107 T 2806 E40010113 e40013480-s8.Hankook 235 75 15 105 H 10059.Goodyear Ultra Grip 225 65 16C 112 R M+S 2307 E13008541 e13009238-s10.Avon Avanza 205 65 16C 107 R11.Nokian WRC 225 65 16C 112 T M+S 1407 E170054159 e1700011-s12.Vanpro Maxxis 225 65 16C 112 R 2007 E4001562-313.Bridgestone Blizzard W800 225 65 16C 112 R M+S 2406 E4001251514.Nokian Hakka C 205 65 16C 107 T 1407 E170054115 e170008-s15.Goodyear Marathon 205 65 16C 103 T 5106 E1300806516.Vanpro Maxxis 205 65 16C 107 T 2107 E4001563117.Hankook RA14 205 65 16C 107 R E40012743 e40014053-s18.Michelin Agilis 51 215 65 16C 106 T M+S 4306 E2001602 e20003602-s19.Michelin Agilis 81 205 65 16C 107 T 2607 E20003601 e20003600-s20.Avon Avanza AV 9 195 65 16C 104 R 307 E11001488

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Photos of the different tyres (except no. 7) are shown in the following.

1. 225 Michelin 2. 225 Goodyear 3. 225 Nokian 4. 225 Sava Trenta

5. 225 Bridgestone 630 6. 225 Avon 8. 235 Hankook

9. 225 Goodyear 10. 225 Avon 11. 225 Nokian WRC 12. 225 Vanpro

13. 225 Bridgestone 14. 205 Nokian 15. 205 Goodyear 16. 205 Vanpro

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17. 205 Hankook 18. 215 Michelin 19. 205 Michelin 20. 195 Avon 3.2.3 C3 tyres The C3 tyres tested are listed in table 3.3. Table 3.3 C3 tyres tested Make Width Ratio Rim Load Speed Type Age Approval Approval1a.Michelin XDA2 495 45 22,5 5800 K LHD 2904 E2005815 e20003729-s1b.Michelin XZA2 315 70 22,5 3550 4306 E2005804 e20003728-s2.Michelin XFA1 385 65 22,5 4250 L 4206 E2002812 e20003734-s3.Nokian NTR844 385 65 22,5 4250 K M+S 3806 E90020444.Nordman NTR45 315 70 22,5 3750 L 407 E400169025.Michelin XZE2 315 70 22,5 3750 I M+S 2207 E2005804 e20003702-s6.Bridgestone M729 315 70 22,5 3550 M M+S 2505 E9002056 e40013987-s7.Michelin XDE2 315 70 22,5 3550 L M+S 2307 E2005803 e20003711-s8.Michelin XDN2 Grip 315 70 22,5 3750 L M+S 4306 E2002815 e20004709-s9.Bridgestone M788 385 65 22,5 4250 K 4706 E9002044 e40013986-s

Photos of the tyres tested are shown in Figure 3.1 and 3.2.

Figure 3.1 From left to right tyre no 1a (bottom), 1b (top), 2, 3, 4, 5 and 6 respectively.

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Figure 3.2 From left to right tyre no 7, 8 and 9 respectively. 3.3 Vehicles used for the tests 3.3.1 Passenger cars C1 tyres were tested using the cars listed in table 3.4. All cars but the V70, which was used to compare the test track of Volvo Torslanda with that of Volvo Hällered, were supplied by Volvo Car Corporation. During the tests the cars, except the V70, were loaded according to the requirements of the tyre directive. Photos of the cars are shown after table 3.4. Table 3.4 Cars used to test C1 tyres. Car type Reg no Total weight Service weightVolvo V70 FCM 403 2100 1570Volvo XC70 FTN 359 2200 1700Volvo XC90 XYA 261 2770 2180Volvo S80 FRS 078 2100 1670Volvo S40 MMR 684 1950 1450

Volvo XC 70 Volvo S40

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Volvo XC 90 Volvo S 80

Volvo V70 3.3.2 Vans, light trucks C2 tyres were tested using the vans listed in table 3.5. All vans were rented or borrowed by SP. During the tests the cars were loaded according to the requirements of the tyre directive. Wherever possible (one exception for one rear axle during one measurement only) the spray shields were dismounted as required by the tyre directive. Photos of the vans are shown after table 3.5. Table 3.5 Vans used to test C2 tyres Van type Reg no Total weight Service weightRenault Master WRH085 3500 2030Dodge Van DPE656 3010 2060VW Transporter CCE304 3000 2080Renault Trafic NLY803 2960 1820Iveco Daily XJM496 3500 2570

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Iveco Renault Master

Dodge Van Renault Trafic

Volkswagen Transporter 3.3.3 Heavy truck C3 tyres were tested using the truck listed in table 3.6. This truck was supplied by Volvo Truck Corporation. The rear spray shield was dismounted but for practical reasons the forward had to remain as shown in the picture. During the tests the truck was loaded according to the requirements of the tyre directive. A photo of the truck is shown after table 3.6. Table 3.6 Truck used to test C3 tyres Van type Reg no Total weight Service weightVolvo FM 4X2 SEO115 20000 6990

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Volvo FM 4X2

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4 Description of the measurement sites 4.1 Volvo Hällered Volvo Hällered has a test track, see figure 4.1, according to ISO 10844, [3], which is used for pass-by measurements on trucks by Volvo Truck Corporation. This track has heating of all relevant surfaces and as trucks are often very close to the type approval limits it is kept in very good condition. The Hällered track was used for all measurements on C2 and C3 tyres.

Figure 4.1 The ISO test track at Volvo Hällered. In contrast to Volvo Car Corporation Volvo Truck Corporation no longer has an accreditation for pass-by measurements. However, they do regular calibrations of track and equipment. Some of the routines are: Test track: The sound absorption of the track surface has been tested by taking core samples from the surface and by making measurements according to the impedance tube method. Frequently the surface is checked with a reference sound source for testing the noise characteristics of the drive-by noise track. The test method is used to check the tracks continuously over time and is used as a complement to the sound absorption measurements. Yearly measurement of the mean texture depth is made. Radar: The radar is calibrated by an accredited laboratory and the calibration interval is 5 years. The radar is also checked by internal routines frequently. Weather station: The weather station is calibrated annually. The weather station includes the barometric pressure, the wind speed, the road surface temperature, the air temperature and the air humidity. The calibration is traceable to relevant standards.

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4.2 Volvo Torslanda

Figure 4.2 The ISO test track at Volvo Torslanda. Volvo Torslanda has a test track according to ISO 10844, [3], which is used for accredited pass-by measurements on cars by Volvo Car Corporation. This track has heating of the driving surface only and as Volvo cars normally have no problems in meeting the relevant limiting values it is not kept in as good condition as the Hällered track. The Torslanda track was used for all measurements on C1 tyres. 4.3 Comparison between the Hällered and the

Torslanda track The two ISO tracks at Volvo Hällered and Volvo Torslanda were compared using a Volvo V70 with Michelin 195/65 R15 tyres. The difference Torslanda – Hällered when measured according to the directive but with normal load and tyre pressure was 2,1 dB. This confirms the subjective impression that the Hällered track was in a better condition than the Torslanda track. According to Volvo Truck Corporation another difference which might explain the difference is that the mean texture depth probably is greater at Hällered than at Torslanda. According to ISO 10844 it should be > 0,4 mm. At Hällered it is about 0,9 mm. The measured sound exposure level difference for the Volvo V70 is shown in frequency bands in figure 4.3.

Volvo V70, 78,9 km/h

35,0

40,0

45,0

50,0

55,0

60,0

65,0

70,0

75,0

20 31 50 80 125

200

315

500

800

1250

2000

3150

5000

8000

Frekvens (Hz)

SEL

(dB

)

Torslanda-rightTorslanda-leftHällered-rightHällered-left

Figure 4.3 Frequency spectra during coast-by at Hällered and Torslanda

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4.4 Nävraspång The site Nävraspång is located at a parking lot at road 180 north of Borås very close to the local road to Volvo Hällered. The width of the road is 9 m, and the posted speed is 90 km/h. It was selected for measurements on C2 and C3 tyres because it is very close to Volvo Hällered where all C2 and C3 measurements took place.

Figure 4.4 Road surface at Nävraspång Measurement site, Nävraspång ABT

(DAC) surface. Table 4.1 summarises the most important data for the site. Table 4.1 Measurement site Nävraspång Measure or description Nävraspång Notes Basic surface type DAC Maximum chipping size 16 mm Age of the surface Approximately 7 years Total traffic exposure (No. of axles passing)

3100 vehicles/day

Composition of traffic (% of heavy vehicles, % of studded tyres)

7.7 % heavy vehicles, 74 % of tyres are studded in wintertime

Posted speed limit 90 km/h Type of road, measured lane National road, 2 lanes, both lanes measured Grade (longitudinal slope) 0 % Condition of surface (subjective, incl homogeneity)

Surface in partly worn cond., tracks visible but not deep, lateral variation clearly visible, binder worn in wheel tracks only

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4.5 Sörredsvägen

Figure 4.5 Test site at Sörredsvägen (The right lane) The Sörredsvägen site was chosen for measurements on C1 tyres as it was the only possible site close to the Volvo Torslanda ISO track. All other major roads in the area had far too heavy traffic to make it possible to carry out coast-by measurements with a reasonable efficiency. The surface was laid in 1999 and it will be replaced in a year or two. It is a 15 mm thick thin layer surface with 11 mm maximum stone size. According to the authorities it should be rather equivalent to a SMA 0/11 surface.

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5 Description of measurements 5.1 Principle Measurements according to the tyre directive are traditional coast-by measurements with the engine switched off and the gear in neutral. 8 complete measurements of the A-weighted maximum sound pressure level, LpAFmax, are carried out at 8 different speeds, 4 equally spaced below a specified reference speed and 4 above. The 8 measurements are used to determine a regression line the equation of which is used to determine LpAFmax at the reference speed. This value is then corrected to a reference road surface temperature of 20ºC using specified temperature coefficients. The final value to compare with regulations is obtained by subtracting 1 dB and rounding downwards to nearest whole decibels. The test vehicle is loaded taking the maximum permissible load of the tyres, the reference load, into consideration. The tyre pressure is a function of total load, reference load and reference pressure, which is normally the maximum permissible pressure. The tyre pressure used during the measurements is normally lower than the tyre pressure used under real driving conditions. The principle used to measure on the ordinary roads was to get one good average value of several coast-bys at the reference speed. 5.2 Test procedure on the ISO tracks. SP used test tracks and equipment for measuring speed and temperature as supplied by Volvo. Both Volvo sites and SP have Swedac accreditation for standardized pass-by measurements. The tyres tested , the vehicles used and the sites used are described in clause 4 and 5. The test geometry included microphones on both sides at a height of 1,2 m and 7,5 m from the centre axis of the vehicle. Tyre pressure and vehicle load was adjusted to comply with the requirements of the directive. The average test load, Qt, shall be 75 + 5% of the reference load Qr which corresponds to the maximum load capacity of the tyre. The tyre inflation pressure, Pt, is given by

25,125,1

1,1 ⎟⎟⎠

⎞⎜⎜⎝

⎛⋅≤≤⎟⎟

⎠

⎞⎜⎜⎝

⎛

r

trt

r

tr Q

QPPQQP (1)

For Class C1 the reference pressure is Pr= 250 kPa for standard tyres and 290 kPa for reinforced tyres. For the other tyres Pr= the maximum permissible pressure of the tyre as given by the marking on the tyre. The axle load was determined before each measurement and additional load was added or removed until the proper value of Qt was reached. This work was carried out by the Volvo personnel assigned to assist SP. The tyre pressure was adjusted to comply with eq. (1) before each measurement. The reference speed, vref, is 80 km/h for Class C1 and Class C2 tyres and 70 km/h for Class C3 tyres. 4 measurements were carried out equally spaced within the range (vref-10) – vref and 4 within the range vref – (vref + 10). The final result was normalized to the test surface reference temperature refϑ = 20ºC using the equation

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)()()( ϑϑϑϑ −+= refRrefR KLL (2)

This correction is carried out for C1 and C2 tyres only and NOT for C3. For C1 tyres the coefficient K is -0,03 dB/ºC when refϑϑ > and -0,06 when refϑϑ ≤ . For C2 tyres K = -0,02 dB/ºC. For the sound pressure level measurements SP used a two-channel realtime analyzer of the make dB 01. 5.3 Test procedure on the roads. In these cases the procedure was the same as on the ISO tracks with the following exceptions:

• No regression line was determined, instead all pass-bys were close to the reference speed and the result was taken as the average

• only one side was measured at a time • no temperature correction was made

SP used its own equipment. The sound pressure level was measured using a Norsonic 140 sound level meter and the speed was measured using a laser speed meter.

28

6 Results 6.1 General The values of the maximum A-weighted sound pressure levels reported in table 6.1, 6.3 and 6.5 have been determined according to the tyre noise directive including temperature correction (for C1 and C2; there is no temperature correction for C3) and using a regression line to determine the value at the reference speed. However, the values are reported both without correction and rounding and with the following correction according to

• first subtract 1 dB • then round downwards to the nearest whole dB

The value given in the right columns of table 6.2, 6.4 and 6.6 is the uncorrected test track value taken from table 6.1, 6.3 and 6.5 respectively. This means that it is normalized to a road surface temperature of 20ºC. As the correction is 0,02 dB/ºC of the road surface temperature, which often was around 30ºC, this reference value should have been about 0,2 dB lower in order to compare around the same temperature. 6.2 C1 tyres The results of the coast-by measurements according to the tyre directive are given in Table 6.1. Table 6.1 indicates that all tyres comply with all requirements laid down in the tyre/noise directive. Looking at the measured results for tyres of different width we find that for d < 215 mm LAFmax = 74,4 dB (calculated average from table 6.1) and for d > 215 mm LAFmax = 75,2. The difference 0,8 dB is very close to the 1,0 dB presumed by the directive. As to extra load tyres there are 5 among the tested ones giving an average of 73 dB. This result does not support the 1 dB “discount” of the directive for extra load tyres.

29

Table 6.1 Test results from the ISO track at Volvo Torslanda Vehicle Tyre type Width/Side/Rim

Load and speed coefficient

maxAFL (dB) Corrected rounded

LAFmax, dB Volvo S40 5. Pirelli P7 standard load 205/55 R16 91V 73,9 72 6. Continental Sport Contact 2

Xtra load 205/50 R17 93W 74,6 73

7. Pirelli Winter 210 MO 205/55 R16 91H 75,7 74 8. Pirelli P7 standard load 205/55 R16 91W 75,3 74 9. ContiWinterContact TS810 195/65 R15 91T M+S 73,7 72 10. Pirelli PZERO Rosso 215/45 R18 93W 73,9 72 Volvo S80 16. Michelin Xtra load 245/45 R17 99W 74,6 73 17. Pirelli PZERO Rosso extra

load 245/40 ZR18 97Y 76,4 75

18. Continental Sport Contact 2

225/50 R17 98W 74,5 73

19. Continental ContiWinter Contact TS810 extra load

225/50 R17 98H M+S 73,1 72

20. Michelin Xtra load 225/50 R17 98W 73,9 72 21. Pirelli P7 standard load 225/55 R16 95W 75,3 74 22. Michelin Pilot Sport 235/35 ZR19 87Y 76,8 75 Volvo XC70 2. Continental 4x4 Contact

Xtra load 215/65 R16 102V M+S 74,0 73

3. Pirelli standard load 235/55 R17 99H M+S 75,9 74 4. Continental 4x4 Contact 235/55 R17 99H M+S 76,1 75 Volvo XC90 11. Continental Cross Contact

UHP but more worn than the other tyres

235/60 R18 103V 75,1 74

12. the same as 11 but 2-3mm less worn

74,8 73

13. Michelin 4x4 Synchrone 235/65 R17 104H M+S 75,0 74 14. ContiWinterContact 4x4 235/65 R17 104H M+S 75,8 74 15. Pirelli PZERO standard

load 255/50 R19 103W 75,1 74

Average Maximum Minimum Standard deviation

74,9 76,8 73,1 1,0

73,4 75 72 1,0

Volvo V70 1. Michelin 195/65 75,01) 741)

1) Tested at normal tyre pressure and service load Comparing the results with the Commission’s proposal for 2012 in table 2.4 which suggests LAFmax = 72 dB, without 1 dB subtraction, we find that no tyre meets this proposal. However, if we assume that the Volvo Torslanda ISO track is 2 dB worse than an optimum ISO track as indicated in 4.3, 8(21) will meet the 2012 proposal. In table 6.2 the results for the normal road is given together with the measured ISO track values without subtraction of 1 dB and without rounding downwards to the nearest whole dB. In addition the relative ranking of the different tyres on the two surfaces is given within parenthesis. 1 indicates the quietest tyre, 2 the second quietest, etc. If there is more than one number within the parenthesis this means that more than one tyre had the same sound pressure level. In figure 6.1 a comparison between the ISO track and the road measurements is made.

30

Table 6.2 Test results on C1 tyres from Sörredsvägen (relative ranking within parenthesis) Vehicle Tyre Average

speed on road

maxAFL (dB)

maxAFL , dBISO track 80 km/h

Volvo S40 MMR 684

5. Pirelli P7 standard load 205/55 R16 91V

80,5 76,8 (1,2)

73,9 (3,4,5)

6. Continental Sport Contact 2 Xtra load 205/50 R17 93W

80,3 78,8 (8) 74,6 (8,9)

7. Pirelli Winter 210 MO 205/55 R16 91H

79,3 80,1 (15)

75,7 (16)

8. Pirelli Winter 210 MO 205/55 R16 91H

77,7 78,1 (4) 75,3 (14,15)

9. ContiWinterContact TS810 195/65 R15 91T M+S

78,3 76,8 (1,2)

73,7 (2)

10. Pirelli PZERO Rosso 215/45 R18 93W

80 79,5 (10,11)

73,9 (3,4,5)

Volvo S80 FRS 078

16. Michelin Xtra load 245/45 R17 99W

81 80,5 (17,18)

74,6 (8,9)

17. Pirelli PZERO Rosso extra load 245/40 ZR18 97Y

79 79,8 (12,13)

76,4 (21)

18. Continental Sport Contact 2 225/50 R17 98W

79,3 78,5 (6) 74,5 (7)

19. Continental ContiWinter Contact TS810 extra load 225/50 R17 98H M+S

81,3 77,8 (3) 73,1 (1)

20. Michelin Xtra load 225/50 R17 98W

78 78,4 (5) 73,9 (3,4,5)

21. Pirelli P7 standard load 225/55 R16 95W

79,5 79,8 (12,13)

75,3 (14,15)

22. Michelin Pilot Sport 235/35 ZR19 87Y

80,3 82,1 (21)

76,8 (21)

Volvo XC70 FTN 359

2. Continental 4x4 Contact Xtra load 215/65 R16 102V M+S

80 79,2 (9) 74,0 (6)

3. Pirelli standard load 235/55 R17 99H M+S

80,3 80,7 (19)

75,9 (19)

4. Continental 4x4 Contact 235/55 R17 99H M+S

77 80,0 (14)

76,1 (20)

Volvo XC90 XYA 261

11. Continental Cross Contact UHP 235/60 R18 103V

80 80,8 (20)

75,1 (12,13)

12. The same as the one above, 2-3mm depper profile

81 80,4 (16)

74,8 (10)

13. Michelin 4x4 Synchrone 235/65 R17 104H M+S

80 80,5 (17,18)

75,0 (11)

14. ContiWinterContact 4x4 235/65 R17 104H M+S

78 78,6 (7) 75,8 (17)

15. Pirelli PZERO standard load 255/50 R19 103W

78,8 79,5 (10,11)

75,1 (12,13)

Average Standard deviation

79,5 1,2

79,4 1,3

74,9 1,0

31

C1-tyres at 80 km/h

727374757677787980818283

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Tyre no

LpFA

max

,7,5

m, d

B

Road<215Road >215ISO <215ISO>215

Figure 6.1 Comparison between the different C1 measurements Table 6.2 and figure 6.1 indicate that the real road used for the measurements is 4,5 dB noisier than the ISO test track. As a comparison the FEHRL report, [4], reports a difference of about 2,5 dB for an SMA 0/10 and 4 dB for an SMA 0/14. Looking at different tyre widths we find that for d < 215 mm LAFmax= 78,5 and for d > 215 mm LAFmax = 79,8 that is a difference of 1,3 dB, which is slightly greater than that of the ISO track but still rather close to 1,0 dB. Comparing the relative ranking of the different tyres we see that there are differences between the ranking on the ISO track and on the normal road but in general it is not too bad. 6.3 C2 tyres In table 6.3 the test results for C2 tyres on the Volvo Hällered ISO track are given and in figure 6.2 a comparison is made with the measurements on the road at Nävraspång..

32

Table 6.3 Test results from the ISO track at Volvo Hällered Vehicle Tyre type Width/side

maxAFL (dB) Corrected rounded LAFmax.

Iveco 2. Goodyear Cargo G26 225/65 73,5 72 4. Sava Trenta 225/65 72,1 71 6. Avon Avanza AV 9 225/65 73,4 72 9. Goodyear Ultra Grip 225/65 M+S 74,0 73 12. Vanpro Maxxis 225/65 73,1 72 13. Bridgestone Blizzard

W800 225/65 M+S 73,2 72

16. Vanpror Maxxis 205/65 72,5 71 19. Michelin Agilis 81 205/65 71,9 70 Master 1. Michelin Agilis 81 225/65 M+S 72,2 71 3. Nokian NRC-2 225/65 72,5 71 5. Bridgestone R630 Duravis 225/65 72,3 71 11. Nokian WRC 225/65 M+S 72,9 71 Trafic 7. Continental Vanco-8 205/70 72,1 71 10. Avon Avanza 205/65 72,2 71 14. Nokian Hakka C 205/65 71,7 70 15. Goodyear Marathon 205/65 71,7 70 17. Hankook RA14 205/65 72,1 71 20. Avon Avanza AV 9 195/65 71,2 70 VW 18. Michelin Agilis 51 215/65 M+S 73,2 72 Dodge 8. Hankook Dynapro HP 235/75 73,5 72 Average

Maximum Minimum

Standard deviation

72,6 74

71,2 0,7

71,2 73 70 0,8

Table 6.3 indicates that all tyres comply with all requirements laid down in the tyre/noise directive. Looking at the measured results for tyres of different width we find that for d < 215 mm LAFmax = 71,9 dB and for d > 215 mm LAFmax = 73,0. The difference 1,1 dB is very close to the 1,0 dB presumed by the directive. Comparing the results with the Commission’s proposal for 2012 in table 2.5 which suggests LAFmax = 71 and 72 (M+S) dB, without 1 dB subtraction, we find that only 6(20) of the tyres tested meet this proposal.

33

Table 6.4 Test results from the road at Nävraspång (relative ranking within parenthesis) Vehicle Tyre type Average

speed km/h

maxAFL (dB)

maxAFL (dB) ISO track 80 km/h

Iveco 2. Goodyear Cargo G26 78 80,0 (9) 73,5 (18,19) 4. Sava Trenta 80,2 79,7 (6) 72,1(5,6,7) 6. Avon Avanza AV 9 78 80,2

(10,11) 73,4 (17)

9. Goodyear Ultra Grip 80 80,5 (12,13,14)

74,0 (20)

12. Vanpro Maxxis 80 81,3 (16) 73,1 (14) 13. Bridgestone Blizzard

W800 79,8 79,1 (2) 73,2 (15,16)

16. Vanpro Maxxis 78,7 81,6 (17,18,19)

72,5 (11,12)

19. Michelin Agilis 81 80,5 79,4 (3) 71,9 (4) Master 1. Michelin Agilis 81 79,3 78,9 (1) 72,2 (8,9) 3. Nokian NRC-2 80 79,9 (8) 72,5 (11,12) 5. Bridgestone R630 Duravis 79 81,7 (20) 72,3 (10) 11. Nokian WRC 79,7 79,6 (4,5) 72,9 (13) Trafic 7. Continental Vanco-8 77,5 80,5

(12,13,14) 72,1 (5,6,7)

10. Avon Avanza 80,8 81,6 (17,18,19)

72,2 (8,9)

14. Nokian Hakka C 82 80,5 (12,13,14)

71,7 (2,3)

15. Goodyear Marathon 81,3 79,8 (7) 71,7 (2,3) 17. Hankook RA14 80,3 80,2

(10,11) 72,1 (5,6,7)

20. Avon Avanza AV 9 79 79,6 (4,5) 71,2 (1) VW 18. Michelin Agilis 51 80,5 81,6

(17,18,19) 73,2 (15,16)

Dodge 8. Hankook Dynapro HP 79 81,1 (15) 73,5 (18,19) Average

Standard deviation 79,7 1,1

80,3 0,9

72,6 0,7

34

C2 tyres at 80 km/h

7071727374757677787980818283

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Tyre no

LpaF

max

,7,5

m, d

B

RoadISO

Figure 6.2 Comparison between the different C2 measurements Table 6.4 and figure 6.2 indicate that the real road used for the measurements is 7,7 dB noisier than the ISO test track. As a comparison the FEHRL report (C1 tyres), [4], reports a difference of about 5 dB for an SMA 0/14. According to Harmonoise, [5], 16 mm chipping size should make 0,5 dB more noise than 14 mm. Looking at different tyre widths we find that for d < 215 mm LAFmax= 80,4 and for d > 215 mm LAFmax = 80,3, that is there is no difference between the widths. Comparing the relative ranking of the different tyres we see that there is little correlation between the ranking on the ISO track and on the normal road.

35

6.4 C3 tyres In table 6.5 the results on the Volvo Hällered ISO track for the tested C3 tyres are given. Table 6.5 Test results for C3 tyres from the ISO track at Volvo Hällered

Vehicle Tyre type Width/Side maxAFL (dB) Corrected

rounded LAFmax.

Volvo FM 1a. SS Michelin XDA2 495/45 75,3 74 2. Michelin XFA1

Steering axle 385/65 72,3 71

3. Nokian NTR 844 Steering axle

385/65 M+S 72,4 71

4. Nordman NTR 45 Driving axle

315/70 74,1 73

5. Michelin XZE2 Steering axle

315/70 M+S 73,0 72

6. Bridgestone M 729 Driving axle

315/70 M+S 75,1 74

7. Michelin XDE2 Driving axle

315/70 M+S 77,4 76

8. Michelin XDN2 Grip Driving axle

315/70 M+S 77,0 76

9. Bridgestone M788 All positions

385/65 75,2 74

Average Max Min

Standard deviation

74,6 77,4 72,3 1,9

73,4 76 71 1,9

Volvo V70 1. Michelin 195/65 72,9 Table 6.5 indicates that all tyres comply with all requirements, also for the future, laid down in the tyre/noise directive. The 3 steering tyres average 72,6 dB whereas the 4 driving tyres average 75,9 dB (excluding super single and the Bridgestone all position tyre). This indicates that the driving axle may yield more tyre/road noise than the other axles. It is interesting to notice that the quietest tyre has a width of 385 mm and not 315 mm. Comparing the results with the Commission’s proposal for 2012 in table 2.6 which suggests LAFmax = 71 and 73 (M+S) dB, without 1 dB subtraction, we find that only 2(9) of the tyres tested meet this proposal. In table 6.6 the results from the road measurements at Nävraspång are given and in figure 6.3 these results are compared with those of the ISO track.

36

Table 6.6 Test results for C3 tyres from the Nävraspång road (relative ranking within parenthesis)

Vehicle Tyre type Average speed (road)

km/h

maxAFL (dB) Road

maxAFL (dB) ISO track 70 km/h

Volvo FM 1a. SS Michelin XDA2 70,6 82,9 (9) 75,3 (7) 2. Michelin XFA1

Steering axle 70,5 80,5 (5) 72,3 (1)

3. Nokian NTR 844 Steering axle

71,2 82,0 (7,8) 72,4 (2)

4. Nordman NTR 45 Driving axle

70,5 79,9 (3) 74,1 (4)

5. Michelin XZE2 Steering axle

69,5 80,1 (4) 73,0 (3)

6. Bridgestone M 729 Driving axle

69 79,2 (1) 75,1 (5)

7. Michelin XDE2 Driving axle

71,0 82,0 (7,8) 77,4 (9)

8. Michelin XDN2 Grip Driving axle

72,0 81,8 (6) 77,0 (8)

9. Bridgestone M788 All positions

69,5 79,2 (2) 75,2 (6)

Average Standard deviation

70,4 1,0

80,8 1,4

74,6 1,9

C3-tyres at 70 km/h

7071727374757677787980818283

1 2 3 4 5 6 7 8 9

Tyre no

LpFA

max

,7,5

m, d

B

Road driveRoad steerISO driveISO steer

Figure 6.3 Comparison between the different C3 measurements Table 6.6 and figure 6.3 indicate that the normal road makes about 6,2 dB more tyre/road noise than the ISO track. The 3 steering tyres average 80,9 dB whereas the 4 driving tyres average 80,7 dB (excluding super single and the Bridgestone all position tyre). This indicates that there is no difference between steering and driving tyres, something that contradicts the results from the ISO track.

37

Comparing the relative ranking of the different tyres we see that there is little correlation between the ranking on the ISO track and on the normal road.

38

7 Conclusions This limited investigation on tyres found on the market in 2007 indicates the following conclusions: There are differences between different ISO tracks. The track used to test C1 tyres was probably about 2 dB louder than the one used to test C2 and C3 tyres. All tyres, C1, C2 and C3, comply with the requirements laid down in the current tyre directive. However, the marginal is not as large as indicated in e.g. the FEHRL report, [4]. At most 50% of the C1 tyres have the potential of meeting the proposed 2012 requirements if tested on an optimum ISO test track. None of the tyres met these proposed values on the ISO track used. 6(20) of the C2 tyres met the 2012 limit values proposed by the Commission. As to C3 tyres 2 (9) tyres met the 2012 proposal. On average the tests carried out on C1 and C2 tyres on ISO tracks confirm the assumption of the directive that wider tyres make more noise and that the 1 dB difference in requirements between C1e and C1d tyres is reasonable provided that one wishes to compensate wider tyres for making more noise. It should be noted, however, that this difference is not found for C2 tyres on a DAC 0/16 road although it is found on the SMA 0/11 for C1 tyres. This investigation does not support that it is necessary to allow for 1 dB more noise from C1 extra load tyres. Based on the rather few measurements on C3 tyres there are strong indications that the drive axle tyres, mostly of M+S type, make considerably (about 3 dB) more noise than steer axle tyres on an ISO test track. However, no difference was found on a normal Swedish DAC 0/16 road. The difference in A-weighted sound pressure level between normal roads and ISO tracks is according to expectations, that is quite large. The difference is about 2 dB greater for C2 tyres than for C3 tyres. Also, as expected, the relative ranking of the different tyres are different between an ISO track and a normal road. Normally the difference is manageable but there are several cases where it is quite significant. In order not to optimize tyres for the present ISO type of road surface only but also for a normal road network it seems necessary to establish a second, alternative road surface with a coarser structure than that of the ISO 10844 surface.

39

8 References [1] Directive 92/23/EEC relating to tyres for motor vehicles and their trailers and to

their fitting [2] Tyre and rim data book, The Scandinavian Tire and Rim Organization [3] ISO 10844:94 Specification of test tracks for the purpose of measuring noise

emitted by road vehicles [4] Study S12.408210 Tyre/road noise, final report, FEHRL (the Forum of European

National Highway Research Laboratories). [5] Source modelling of road vehicles, HAR11TR-041210-SP10 [6] Public consultation on outline proposals for a Regulation of the European

Parliament and of the Council on Advanced Safety Features and Tyres

SP Technical Research Institute of Sweden Box 857, SE-501 15 BORÅS, SWEDEN Telephone: +46 10 516 50 00, Telefax: +46 33 13 55 02 E-mail: info@sp.se, Internet: www.sp.se www.sp.se

Energy Technology SP Report 2007:70 ISBN 978-91-85829-02-6 ISSN 0284-5172

SP Technical Research Institute of Sweden develops and transfers technology for improving competitiveness and quality in industry, and for safety, conservation of resources and good environment in society as a whole. With Sweden’s widest and most sophisticated range of equipment and expertise for technical investigation, measurement, testing and certification, we perform research and development in close liaison with universities, institutes of technology and international partners. SP is a EU-notified body and accredited test laboratory. Our headquarters are in Borås, in the west part of Sweden.