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How to Understand Your Car Tyres

The markings on your tyre sidewall can be a little confusing. The combination of numbers and letters all define different elements of your tyres such as the width, load rating, rim diameter and speed rating. With our help, you will easily be able to understand your vehicle’s tyre markings.

To start off, the below image shows a tyre with a mixture of numbers and letters: 205 55 R16 91W

Tyre with Tyre Size and information highlighted

To clearly understand each element of the tyre size, please see the below table:

Sidewall Marking

Explanation

The first 3 numbers e.g. 205

The width of the tyre in millimetres

The fourth and fifth numbers e.g. 55

A percentage of the tyre width, or otherwise known as the profile height.

The first letter e.g. R

The tyre is of Radial construction

The two numbers following the first letter e.g. 16

The tyre’s inner rim diameter in inches

The last two numbers e.g. 91

The Load Rating of the tyre

The second and final letter e.g. W

The Speed Rating which indicates the tyre’s maximum speed at full load

As well as these numbers and letters, you will notice a smaller combination of numbers and letters next to them. These represent the date of manufacture, whether the tyres have been reinforced, whether they are run flat and which car manufacturer the tyres are most suited for.

Tyre with Date of Manufacture and other informtion highlighted

You can read more about these tyre elements, as well as others, by clicking the text below.

Tyre Size
What is Tyre Speed Rating?
What is Tyre Load Rating?
Where can i gind the Tyre Date of Manufacture?
What does Reinforced mean on tyres?
Are my tyres Run Flat Tyres?
What is Homologation

Tyre Size

Your tyre size is the sequence of numbers and one letter that is 8 digits long. This looks like this: 205 55 R16, but each element can differ depending on your car and your wheels. It is crucial to check your current tyre sizes or your vehicle handbook before changing your tyres, as not all tyres will fit or be well-suited for your vehicle.

As discussed within the table above, these numbers include the tyre width, aspect ratio, radial and wheel diameter of your tyres.

What is Tyre Speed Rating?

Speed rating of a tyre is presented after the tyre size combination in the form of a letter. Each letter relates to a maximum speed that the tyres can perform. Although on the British roads these speed limits should never be reached, it is important to understand the absolute limit that your tyres can physically perform.

See the table below for more information on Speed Rating:

Speed Rating

Maximum Speed

Q

99mph

R

106mph

S

112mph

T

118mph

H

131mph

V

149mph

W

168mph

Y

186mph

What is Tyre Load Rating?

The tyre load rating shows the maximum weight each tyre is able to carry. It is important to take note of this information; carrying an incorrect load capacity in your vehicle can cause driving issues, invalidate your insurance or damage your car.

See the below table for the weight capacity in kg of each possible load rating:

Load Index

Load in kg

62

265

63

272

64

280

65

290

66

300

67

307

68

315

69

325

70

335

71

345

72

355

73

365

74

375

75

387

76

400

77

412

78

425

79

437

80

450

81

462

82

475

83

487

84

500

85

515

86

530

87

545

88

560

89

580

90

600

91

615

92

630

93

650

94

670

95

690

100

710

101

825

102

850

103

875

104

900

105

925

Where can I find the Tyre Date of Manufacture?

Your tyres will always be handily printed with information that informs you of when and where your tyres were manufactured. Following the tyre size, speed and load rating is the date of manufacture.

This information begins with the letters DOT, meaning the tyre exceeds Department of Transport safety standards.

After DOT, there are characters that are only applicable to individual manufacturers. These are displayed to identify which production facility it was made in and which exact tyre it is.

The last four numbers present the week and then the year of which the tyre was manufactured. For example, 1417 means that the tyre was created in the 14th week of 2017.

What does Reinforced mean on tyres?

Sometimes your tyres may have the word ‘Reinforced’ printed on the sidewall; or perhaps it is a two to five long combination of letters. In the table below, we explain what these letters mean.

If your tyres have an increased load rating they have an indication on the sidewall to show that they have been reinforced to handle the weight. It can often vary depending on your manufacturer.

‘Reinforced’ Combination

Definition

XL

Extra Load

EXL

Extra Load

RF

Reinforced

REINF

Reinforced

RFD

Reinforced

Are my tyres Run Flat Tyres?

If your tyres are Run Flat Tyres you will see a small combination of letters displayed after the date of manufacture.

Run Flat’s are specially manufactured tyres that boast strengthened sidewalls. This helps to avoid losing pressure in the case of a puncture, ultimately holding the weight of the vehicle until it is possible to be replaced.

Below is a table that represents the different kinds of Run Flat Tyre combinations you may see on your tyres:

Letter Combination

Definition

Manufacturer

RFT

Run Flat Technology

Pirelli, Firestone, Bridgestone

EMT

Extended Mobility Technology

Goodyear

ROF

RunOnFlat

Goodyear

DSST

Dunlop Self Supporting Technology

Dunlop

SSR

Self-Supporting Run Flat

Continental

MOE

Michelin Run Flat

Michelin

ZP

Zero Pressure

Michelin

What is Homologation?

Depending on the tyres that you buy, you may see another combination of letters after the Run Flat digits.

These letters are the homologation of the tyre; this means the tyres were designed to be specifically used for certain vehicle manufacturers.

Most well-known and prestigious brands have their own designated symbol to show that they have met the tyre manufacturer’s safety standards and have been given an OE status.

Refer to the table below for more information regarding particular manufacturer’s homologation symbols:

Homologation Symbol

Manufacturer

A0

Audi

R0

Audi Quattro and S variants

A

Toyota Auris

G

Volkswagen Golf

VO

Volkswagen Touareg

LRO

Land Rover

FO

Ford

MO

Mercedes

MO1

Mercedes AMG

J

Jaguar

N0, N1, N2, N3, N4, N5, N6

Porsche

AR, AZ

Alfa Romeo

MOE

Mercedes Run Flat

BMW and Mini