861 Car tyres

Current tyres are marked in accordance with the standards agreed by the European Tyre and Rim Technical Organisation. Tyres with cross-ply construction and normal 82% aspect ratio do not indicate these features but radial construction and lower aspect ratios are indicated. Tyre section width, speed capacity, wheel rim diameter and tread pattern are always indicated.

Example 1

165 or 185 = nominal section width of tyre in millimetres

70 = 70% aspect ratio (Note no figures following 165 indicates 82% aspect ratio) S or V = letter indicates speed capability

13 or 15 = nominal wheel rim diameter in inches

MX, XWX = manufacturer's tread pattern

In some instances section width is indicated in inches.

Example 2 6.45 Q 14

6.45 = nominal section width of tyre in inches Q = letter indicates speed capability

(speed symbol Q=160 km/h) 14 = nominal wheel rim diameter in inches

Note No aspect ratio or construction indicated. Therefore assume 82% aspect ratio and cross-ply construction.

A revised form of marking has been introduced to include the maximum speed and load carrying capacity of the tyre under specified operating conditions.

A letter symbol indicates the maximum speed (Table 8.1) and a numerical code will identify the load carrying capacity (Table 8.2).

Example of new form of marking MXV

205 = normal section width in millimetres

70 =70% aspect ratio

R =radial construction

13 =nominal wheel rim diameter in inches

S = speed symbol (from Table 8.1: S = 180 km/h) MXV = manufacturer's tread pattern code

Table 8.1 Speed symbols (SS)

Speed

Speed

SS Speed

SS Speed SS

Speed

symbol

(km/h)

(km/h)

(km/h)

(km/h)

(SS)

A4

20

E 70

L

120

R

170

A6

30

F 80

M

130

S

180

A8

40

G 90

N

140

T

190

B

50

J 100

P

150

U

200

C

60

K 110

Q

160

H

210

(V =

over 210)

Table 8.2 Load index (LI)

LI kg

LI

kg LI

kg

LI

kg

10 60

80

450 150

3350

220

25000

20 80

90

600 160

4500

230

33500

30 106

100

800 170

6000

240

45000

40 140

110

1060 180

8000

250

60000

50 190

120

1400 190

10600

260

80000

60 250

130

1900 200

14000

270

106000

70 335

140

2500 210

19000

280

140000

8.6.2 Light, medium and heavy truck tyres Truck tyres sometimes include ply rating which indicates the load carrying capacity.

Example 10 R 20.0 PR12 XZA

10 = nominal section width of tyre in inches

R = radial construction

20.0 = nominal wheel rim diameter in inches

PR12 = ply rating

XZA = manufacturer's tread pattern

The revised form of marking indicates the load carrying capacity and speed capability for both single and twin wheel operation. The ply rating has been superseded by a load index because with improved fabric materials such as rayon, nylon and polyester as opposed to the original cotton cord ply, fewer ply are required to obtain the same strength using cotton as the standard, and therefore the ply rating does not give an accurate indication of tyre load bearing capacity.

Example 295/70 R 22.5 Tubeless 150/140L XZT

295 = nominal section width of tyre in millimetres 70 = 70% aspect ratio R = radial construction 22.5 = nominal rim diameter in inches 150 = load index for singles (from

Table 8.2: 150 = 3350 kg per tyre) 140 = load index for twins (from

Table 8.2: 140 = 2500 kg per tyre) L = speed symbol (from Table 8.1:

L = 120 km/h) XZT = manufacturer's tread pattern

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