Document ID: chunk:federal_register_of_legislation:F2018L01517:front:0:p5
Version: federal_register_of_legislation:F2018L01517
Segment Type: other
Provision Reference: 
Character Range: 13067–15740

the part of a tyre which is of such shape and structure as to fit the rim and to hold the tyre on it[3];
2.8. "Cord" means the strands forming the fabric of the plies in the tyre3;
2.9. "Ply" means a layer of rubber-coated parallel cords3;
2.10. "Carcass" means that part of a tyre other than the tread and the rubber sidewalls which, when inflated, bears the load3;
2.11. "Tread" means that part of a pneumatic tyre which comes into contact with the ground, protects the carcass against mechanical damage and contributes to ground adhesion3;
2.12. "Sidewall" means the part of a tyre between the tread and the area designed to be covered by the rim flange3;
2.13. "Lower sidewall" means the area included between the line of maximum section width of the tyre and the area designed to be covered by the rim flange3;
2.13.1. However, in case of tyres identified by the "tyre to rim fitment configuration" (see paragraph 3.1.12.) symbol "A", it means the area of the tyre which is seating on the rim;
2.14. "Tread groove" means the space between two adjacent ribs and/or blocks in the tread pattern3;
2.15. "Section width (S)" means the linear distance between the outsides of the sidewalls of an inflated tyre, excluding elevations due to labelling (marking), decoration or protective bands or ribs3;
2.16. "Over-all width" means the linear distance between the outsides of the sidewalls of an inflated tyre, including labelling (marking), decoration and protective bands or ribs3;
2.17. "Section height (H)" means a distance equal to half the difference between the outer diameter of the tyre and the nominal rim diameter;
2.18. "Nominal aspect ratio (Ra)" means one hundred times the number obtained by dividing the number expressing the section height (H) by the number expressing the nominal section width (S1), both dimensions expressed in the same units;
2.19. "Outer diameter (D)" means the overall diameter of an inflated new tyre3;
2.20. "Tyre-size designation" means:
2.20.1. A designation showing:
2.20.1.1. The nominal section width (S1).  This width must be expressed in mm, except in the case of types of tyre for which the size designation is shown in the first column of the tables in Annex 5 to this Regulation;
2.20.1.2. The nominal aspect ratio, except in the case of certain types of tyre for which the size designation is shown in the first column of the tables in Annex 5 to this Regulation or, depending on the tyre design type, the nominal outer diameter expressed in mm;
2.20.1.3. A conventional number "d" (the "d" symbol) denoting the nominal diameter of the rim and corresponding to its diameter expressed either in codes (number below 100) or in