# What tire markings mean

When buying a new tire or when we just want to check the parameters and performances of our current vehicle tires, we need to read the tire side markings. The numbers and symbols found on the sidewall of every tire give significant details about their size, performance and manufacturing dates.

The most common and visible marking is the size marking. The symbol for size has the following format:

TireWidth [mm] / AspectRatio [%] Construction RimDiameter [in]

Example: 225/60R18

Image: BF Goodrich Advantage tire marking

The tire width (255), in millimeters, is the distance measured from sidewall to sidewall.

The aspect ratio (60), in percentage, is the ratio between the tire height and width.

$\text{Aspect Ratio [%]}=\frac{\text{Tire Height [mm]}}{\text{Tire Width [mm]}} \cdot 100$

An aspect ratio of 60 means that the height of the tire is equal to 60% of the tire’s width. The higher the aspect ratio, the higher the height of the tire. Off road tires have high aspect ratio since tire height is good for rocky, bumpy roads. Sports, high performance tires have low aspect ratio, since the lower the height of the tire, the better is the stability of the vehicle and the grip of the wheel.

Image: Tire size and aspect ratio

The construction symbol gives details about the inside layers of the tire (plies), how are they arranged across the tire. The most common type of tires is the Radial tire (R). There are also Diagonal tires (D) or Belted (B).

The wheel/rim diameter, in inches, is the external diameter of the wheel/rim. It is also the internal diameter of the tire.

The are also additional markings after the size marking. These are the load index and the speed index.

TireWidth [mm] / AspectRatio [%] Construction RimDiameter [in] LoadIndex SpeedIndex

Example: 245/40R18 97V

Image: Continental Winter Contact tire marking

The load index (LI) indicates the maximum weight supported by the tire when properly inflated. For example the load index 97 means that the tire can withstand 730 kg of load (weight).

A comprehensive load index table is below:

 LI kg LI kg LI kg LI kg LI kg LI kg LI kg 0 45 25 92.5 50 190 75 387 100 800 125 1650 150 3350 1 46.2 26 95 51 195 76 400 101 825 126 1700 151 3450 2 47.5 27 97.5 52 200 77 412 102 850 127 1750 152 3550 3 48.7 28 100 53 206 78 425 103 875 128 1800 153 3650 4 50 29 103 54 212 79 437 104 900 129 1850 154 3750 5 51 30 106 55 218 80 450 105 925 130 1900 155 3850 6 53 31 109 56 224 81 462 106 950 131 1950 156 4000 7 54.5 32 112 57 230 82 475 107 975 132 2000 157 4125 8 56 33 115 58 238 83 487 108 1000 133 2060 158 4250 9 58 34 118 59 243 84 500 109 1030 134 2120 159 4375 10 60 35 121 60 250 85 515 110 1060 135 2180 160 4500 11 61.5 36 125 61 257 86 530 111 1090 136 2240 161 4625 12 63 37 128 62 265 87 545 112 1120 137 2300 162 4750 13 65 38 132 63 272 88 560 113 1150 138 2360 163 4875 14 67 39 136 64 280 89 580 114 1180 139 2430 164 5000 15 69 40 140 65 290 90 600 115 1215 140 2500 165 5150 16 71 41 145 66 300 91 615 116 1250 141 2575 166 5300 17 73 42 150 67 307 92 630 117 1285 142 2650 167 5450 18 75 43 155 68 315 93 650 118 1320 143 2725 168 5600 19 77.5 44 160 69 325 94 670 119 1360 144 2800 169 5800 20 80 45 165 70 335 95 690 120 1400 145 2900 170 6000 21 82.5 46 170 71 345 96 710 121 1450 146 3000 171 6150 22 85 47 175 72 355 97 730 122 1500 147 3075 172 6300 23 87.5 48 180 73 365 98 750 123 1550 148 3150 173 6500 24 90 49 185 74 375 99 775 124 1600 149 3250 174 6700

The speed index (SI) or speed rating, indicates the maximum speed which can be withstand by the tire. Usually the speed index of the tire is matching the maximum speed of the vehicle. For example, the speed index V means that the maximum speed capability of the tire is 240 kph.

A comprehensive speed index table is below:

 SI Maximum Speed [kph] SI Maximum Speed [kph] A1 5 L 120 A2 10 M 130 A3 15 N 140 A4 20 p 150 A5 25 Q 160 A6 30 R 170 A7 35 S 180 A8 40 T 190 B 50 U 200 C 60 H 210 D 65 V 240 E 70 Z over 240 F 80 W 270 G 90 (W) over 270 J 100 Y 300 K 110 (Y) over 300

The manufacturing date of the tire is usually displayed by four digits inside an oval filed. For example 2514 means that the tire was produced in the 25th week of the year 2014.

A special marking is for winter tires. If the tire has the symbols M+S (Mud and Snow), it’s designed to achieve better values for handling and traction in winter conditions, compared with a summer tire (without M+S marking).

Image: Tire identification diagram

The snow flake symbol also known as 3PMSF (Three Peak Mountain Snow Flake) symbol is is also related to winter tires and it’s required by North American legislation.

Tires can also have traction and temperature grades. The traction grade indicates the wet traction performance of the tire under controlled testing conditions. A tire with an “AA” traction rating has outstanding traction performance in wet conditions. Traction grades can be: AA, A, B or C

Temperature grade indicates the capacity of the tire to withstand high temperature. A tire with a high temperature grade can operate at higher vehicle speeds. The best temperature grade is A, followed by B (medium) and C (low).

Treadwear grades are set based on standardized government tests, which predict the expected treadwear of a tire. For example, a tire with a treadwear grade of 220 should last twice as long as a tire with a treadwear grade of 110.

Introduced by the Economic Commission for Europe (ECE), the tire E mark is now mandatory on all European tires. It also signals that the tire meets certain requirements in terms of sizing, performance and marking. For example E4 enclosed in a circle means that the tire was produced and approved in Netherlands.

A comprehensive E mark table is below:

 Code Country Code Country E1 Germany E21 Portugal E2 France E22 Russian Federation E3 Italy E23 Greece E4 Netherlands E24 Ireland E5 Sweden E25 Croatia E6 Belgium E26 Slovenia E7 Hungary E27 Slovakia E8 Czech Republic E28 Belarus E9 Spain E29 Estonia E10 Yugoslavia E31 Bosnia and Herzegovina E11 United Kingdom E32 Latvia E12 Austria E34 Bulgaria E13 Luxembourg E37 Turkey E14 Switzerland E40 Macedonia E16 Norway E43 Japan E17 Finland E45 Australia E18 Denmark E46 Ukraine E19 Romania E47 South Africa E20 Poland E48 New Zealand

Starting with November 2012 all new tires sold in the European Union (EU) must be provided with a standardized tire label. The information on the label is related to three tire properties:

• rolling resistance
• grip in wet conditions

Image: EU standardized tire label

The labels are divided in three categories: C1 (passenger vehicles), C2 (light utility vehicles) and C (heavy commercial vehicles). Best grade is A, worst is G.

The maximum permissible inflation pressure (e.g. 45 psi = 3.1 bar) is the maximum air pressure at which the tire can be inflated. This pressure should be much higher than the nominal working pressure of the tire (e.g. 2.1 bar).

For any questions or observations regarding this tutorial please use the comment form below.

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