Council directive 92/23/EEC (repealed)Show full title

2. For the purposes of this Directive: U.K.

2.1. ‘type of tyre’ means a category of tyres which do not differ in such essential respects as: U.K.

2.1.1. manufacturer's name or trade mark; U.K.

2.1.2. tyre-size designation; U.K.

2.1.3. category of use: U.K.

— normal

:

normal road-use tyre,

— special

:

special-use tyre, e.g. tyre for mixed use (both on and off the road) and at restricted speed,

• snow tyre,

• temporary-use spare tyre;

2.1.4. structure (diagonal (bias-ply), bias-belted, radial-ply); U.K.

2.1.5. speed category; U.K.

2.1.6. load capacity index; U.K.

2.1.7. tyre cross-section; U.K.

2.2. ‘snow tyre’ means a tyre the tread pattern and structure of which are primarily designed to ensure in mud and fresh or melting snow a performance better than that of a normal tyre. The tread pattern of a snow tyre generally consists of groove (rib) and/or solid-block elements more widely spaced than on a normal tyre; U.K.

2.3. ‘structure’ of a tyre means the technical characteristics of the tyre's carcass. The following structures are distinguished in particular: U.K.

2.3.1. ‘diagonal’ or ‘bias-ply’ describes a tyre structure in which the ply cords extend to the bead and are laid at alternate angles of substantially less than 90^o to the centreline of the tread; U.K.

2.3.2. ‘bias-belted’ describes a tyre structure of diagonal (bias-ply) type in which the carcass is restricted by a belt comprising two or more layers of substantially inextensible cord material laid at alternate angles close to those of the carcass; U.K.

2.3.3. ‘radial’ describes a tyre structure in which the ply cords extend to the beads and are laid substantially at 90^o to the centreline of the tread, the carcass being stabilized by an essentially inextensible circumferential belt; U.K.

2.3.4. ‘reinforce’ describes a tyre structure in which the carcass is more resistant than that of the corresponding standard tyre; U.K.

2.3.5. ‘temporary-use spare tyre’ means a tyre different from a tyre intended to be fitted to any vehicle for normal driving conditions; but intended only for temporary use under restricted driving conditions; U.K.

2.3.6. ‘T-type temporary-use spare tyre’ means a type of temporary-use spare tyre designed for use at inflation pressure higher than those established for standard and reinforced tyres; U.K.

2.4. ‘bead’ means the part of a tyre which is of such shape and structure as to fit the rim and hold the tyre on it(1); U.K.

2.5. ‘cord’ means the strands forming the fabric of the plies in the tyre(1); U.K.

2.6. ‘ply’ means a layer of rubber-coated parallel cords(1); U.K.

2.7. ‘carcass’ means that part of a tyre other than the tread and the rubber sidewalls which, when inflated, bears the load(1); U.K.

2.8. ‘tread’ means that part of a tyre which comes into contact with the ground(2); U.K.

2.9. ‘sidewall’ means the part of the tyre, excluding the tread, which is visible when the tyre, fitted to a rim, is viewed from the side(2); U.K.

2.10. ‘lower sidewall’ means the area below the line of maximum section width of the tyre, which is visible when the tyre, fitted to a rim, is viewed from the side(2); U.K.

2.11. ‘tread groove’ means the space between the adjacent ribs or blocks in the tread pattern(2); U.K.

2.12. ‘section width’ 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 ribs(2); U.K.

2.13. ‘overall width’ means the linear distance between the outsides of the sidewalls of an inflated tyre, including labelling (marking), decoration and protective bands or ribs(2); U.K.

2.14. ‘section height’ means a distance equal to half the difference between the outer diameter of the tyre and the nominal rim diameter(2); U.K.

2.15. ‘nominal aspect ratio Ra’ means one hundred times the number obtained by dividing the number expressing the nominal section height in millimetres by the number expressing the nominal section width in millimeters; U.K.

2.16. ‘outer diameter’ means the overall diameter of an inflated new tyre(2); U.K.

2.17. ‘tyre-size designation’: U.K.

2.17.1. means a designation showing: U.K.

2.17.1.1. the nominal secton width. This width must be expressed in mm, except in the case of tyres for which the size designation is shown in the first column of the tables in Appendix 5; U.K.

2.17.1.2. the nominal aspect ratio, except in the case of tyres for which the size designation is shown in the first column of the tables in Appendix 5; U.K.

2.17.1.3. a conventional number ‘d’ (the ‘d’ symbol) denoting the nominal rim diameter and corresponding to the diameter of the rim expressed either in inches (number below 100 — see table) or in mm (numbers above 100) but not both. U.K.

The exhaustive range of values is shown in the table below:
‘d’Nominal rim diameter (the symbol)
Expressed in inches(code)	Equivalence in mm(reference section 6.1.2.1)
10	254
11	279
12	305
13	330
14	356
15	381
16	406
17	432
18	457
19	483
20	508
21	533
22	559
24	610
25	635
14,5	368
16,5	419
17,5	445
19,5	495
20,5	521
22,5	572
24,5	622

2.17.1.4. the letter ‘T’ in front of the nominal section width in case of T-type temporary-use spare tyres; U.K.

2.18. ‘nominal rim diameter (d)’ means the diameter of the rim on which a tyre is designed to be mounted(3); U.K.

2.19. ‘rim’ means the support for a tyre-and-tube assembly, or for a tubeless tyre, on which the tyre beads are seated(3); U.K.

2.20. ‘theoretical rim’ means the notional rim whose width would be equal to x times the nominal section width of a tyre; the value ‘x’ must be specified by the tyre manufacturer; U.K.

2.21. ‘measuring rim’ means the rim on which a tyre must be fitted for size measurements; U.K.

2.22. ‘test rim’ means the rim on which a tyre must be fitted for testing; U.K.

2.23. ‘chunking’ means the breaking away of pieces of rubber from the tread; U.K.

2.24. ‘cord separation’ means the parting of the cords from their rubber coating; U.K.

2.25. ‘ply separation’ means the parting of adjacent plies; U.K.

2.26. ‘tread separation’ means the pulling away of the tread from the carcass; U.K.

2.27. ‘tread-wear indicators’ mean projections within the tread-grooves designed to give a visual indication of the degree of wear of the tread; U.K.

2.28. ‘load-capacity index’ means one or two numbers which indicate the load the tyre can carry in single or in single and dual formation at the speed corresponding to the associated speed category and when operated in conformity with the requirements governing utilization specified by the manufacturer. The list of these indices and their corresponding masses is given in Annex II, Appendix 2; U.K.

2.28.1. on passenger car tyres there must be one load index only; U.K.

2.28.2. on commercial vehicle tyres there may be one or two load indices, the first one for single formation and the second one, when present, for dual (twin) formation in which case the two indices are divided by a slash (/); U.K.

2.28.3. a type of tyre may have either one or two sets of load capacity indices depending on whether or not the provisions of section 6.2.5 are applied; U.K.

2.29. ‘speed category’, expressed by the speed category symbol as shown in the table in 2.29.3; U.K.

2.29.1. in the case of a passenger car tyre, the maximum speed which the tyre can sustain; U.K.

2.29.2. in the case of a commercial vehicle tyre, the speed at which the tyre can carry the mass corresponding to the load capacity index; U.K.

2.29.3. The speed categories are as shown in the table below: U.K.

Speed category symbol	Corresponding speed(km/h)
F	80
G	90
J	100
K	110
L	120
M	130
N	140
P	150
Q	160
R	170
S	180
T	190
U	200
H	210
V	240

2.29.4. tyres suitable for maximum speeds higher than 240 km/h are identified by means of the letter code ‘Z’ placed within the tyre size designation; U.K.

2.29.5. a type of tyre may have either one or two sets of speed category symbols depending on whether or not the provisions of section 6.2.5 are applied; U.K.

2.30. ‘table: Variation of load capacity with speed’ means: the table, in Annex II Appendix 8, showing as a function of the load capacity indices and nominal speed category symbols the load variations which a tyre can withstand when used at speeds different from that corresponding to its speed category symbol; U.K.

2.30.1. the load variations do not apply in the case of passenger car tyres nor, in the case of commercial vehicle tyres, to the additional load capacity indices and speed category symbol when the provisions of section 6.2.5 are applied; U.K.

2.31. ‘maximum load rating’ means the maximum mass the tyre is rated to carry: U.K.

2.31.1. in the case of passenger car tyres suitable for speeds not exceeding 210 km/h, the maximum load rating must not exceed the value associated with the load capacity index of the tyre; U.K.

2.31.2. in the case of passenger car tyres suitable for speeds exceeding 210 km/h, but not exceeding 240 km/h (tyres classified with speed category symbol ‘V’), the maximum load rating must not exceed the percentage of the value associated with the load capacity index of the tyre, indicated in the table below, with reference to the speed capability of the vehicle to which the tyre is fitted; U.K.

Maximum speed(km/h)	Load(%)
215	98,5
220	97
225	95,5
230	94
235	92,5
240	91

for intermediate maximum speeds linear interpolations of the maximum load rating are allowed;

2.31.3. for speeds exceeding 240 km/h (‘Z tyres’) the maximum load rating must not exceed the value specified by the tyre manufacturer with reference to the maximum speed capability of the vehicle to which it is fitted; U.K.

2.31.4. in the case of commercial vehicle tyres, the maximum load rating, both for single and for dual formation, must not exceed the percentage of the value associated with the relevant load capacity index of the tyre as indicated in the table ‘Load-capacity variation with speed’ (see 2.30), with reference to the speed category symbol of the tyre and the speed capability of the vehicle to which the tyre is fitted. When additional load capacity indices and speed category symbols apply, those too are considered to determine the maximum load rating of the tyre; U.K.

2.32. ‘passenger car tyre’ means a tyre designed primarily, but not only, for passenger cars (motor vehicles in category M1) and their trailers (01 and 02); U.K.

2.33. ‘commercial vehicle tyre’ means a tyre designed primarily, but not only, for vehicles other than passenger cars (motor vehicles in categories M2, M3, N) and their trailers (03, 04); U.K.

2.34. ‘tyre ground pressure (F/Ac)’ means the average until load transmitted by the tyre, through its contact area, to the road surface expressed as the ratio between the vertical force (F), in static conditions on the axis of the wheel and the tyre contact area (Ac) measured with the tyre inflated at the cold inflation pressure recommended for the intended type of service. It is expressed in kN/m²; U.K.

2.35. ‘tyre contact area (Ac)’ means the area of the flat surface contained within the virtual perimeter of the tyre footprint. It is expressed in m²; U.K.

2.36. ‘virtual perimeter of the tyre footprint’ means the convex polygonal curve circumscribing the smallest area containing all points of contact between the tyre and the ground; U.K.

2.37. ‘cold inflation pressure’ means the internal pressure of the tyre with the tyre at ambient temperature and does not include any pressure build up due to tyre usage. It is expressed in bar kPa. U.K.

(1)

See explanatory figure, Appendix 1.

(2)

See explanatory figure, Appendix 1.

(3)

See explanatory figure, Appendix 1.