Abstract
This paper deals with the legal demands and its consequences of both Regulations (UN/ECE) No. R 117 and (EU) No. 1235/2011, with regards to the tyre wet grip performance for Passenger Car tyres C1, Light Commercial Vehicle tyres C2 and Truck and Bus tyres C3.
The Geneva international UN/ECE Regulation No. 117, valid from Oct. 2009, has defined only one wet grip index G for Passenger Car tyres C1 with G≥1.1. Light Truck tyres C2 and Truck and Bus tyres C3 were not covered in this international Regulation.
The current Brussels EU Regulation No. 1235/2011, valid from May 30, 2012, has in contrast introduced a European Tyre Label with wet grip index G classes from A to G for Passenger Car tyres C1, Light Commercial Vehicles tyres C2 and Truck/Bus tyres C3. Every wet grip class for each vehicle category has a defined band of numerical values for the wet grip index G. The legislated wet grip values G in this Regulation are very low, given the state of the art for tyre manufacturing and resultant safety on European Roads. (Note: In addition, this Regulation (EU) No. 1235/2011 has NO lower wet grip limit set for the wet grip index G with tyres in wet grip class F in any of the vehicle categories C1, C2 or C3!)
The Paper compares measurements of braking distances on vehicles with tyres of different wet grip classes in line with the proposed changes for C1 tyres in UN/ECE R 117 and its proposed numerical amendment to C2 and C3 tyres. These proposed changes and amendments are carbon copies of the wet grip values G in Regulation (EU) No. 1235/2011 for the European Tyre Label, with the vital distinction, that in the above UN/ECE R 117 proposal, at least the lower limits of tyre class F are correctly defined.
The measured braking distances and corresponding impact speeds of the test vehicles, by using tyres with wet grip indices G according to the proposed amendments of UN/ECE R 117 on vehicles of all classes, are showing very critical results. For example a passenger car braking from 100 km/h with budget-tyres of class F compared to one with premium tyres of class A shows an increased stopping distance of about 25m in the extreme. This vehicle will therefore hit the already stationary vehicle in front of it with a remaining impact speed of about 58 km/h. A Bus will impact with about 75 km/h.
EVU welcomes the new European Tyre Label Regulation. Independent market surveillance should be introduced in addition as focal point to the concepts of monitoring this regulation. (The current EU regulation calls for a “self-certification of the tyre manufacturers” only.)
The Regulation No. 1235/2011 of the European Parliament and the Council for Type Approval of vehicles (EU) as well as the Regulation No. 117.02 of the Economic Commission of the United Nations for Europe (UN/ECE) should be changed in such a way, that for C1-tyres (normal passenger cars) the minimum wet grip index G is 1.25. All C2-tyres (light commercial vehicles) should at least meet a minimum wet grip index of G = 1.1. All C3-tyres (heavy trucks and busses) should at least meet a minimum wet grip index of G = 0.95.
All C1-winter tyres should at least meet the demand of the minimum wet grip value G of 1.15. The minimum wet grip value for C2-winter tyres should be 0.95 and for C3-winter tyres it should be 0.85.
The listed official document “ECE/TRANS/WP.29/GRRF/2013/9, Proposal for Amendments to Regulation No. 117”, dated 7th of December 2012, as discussed in the 74th session of GRRF, 19th- 21st of February 2013, should be changed according to the above requested and listed minimum wet grip values G for C1-, C2- and C3-tyres. Wet grip classes D, E, F and G could therefore be eliminated.
Due to the missing lower limits for G in the wet grip class F for C1, C2 and C3 tyres according to Commission Regulation (EU) No. 1235/2011, officially valid from 30 May 2012, a tyre-to-road coefficient of adhesion in the extreme of 0 (zero) is legally permitted. This is an apparent flaw in above cited EU regulation, which causes a potential danger to the road traffic safety for all motor vehicles in Europe with such tyres. It is strongly recommended, that the wet grip class F is urgently removed with top priority from said EU regulation, since a direct liability of the responsible EU Commission can not be excluded.
KEYWORDS: UN/ECE- and EU-Tyre Regulations, wet grip index, vehicle braking tests, EU-Tyre Label, accident analysis