Labels and measuring units:

1. Tyre manufacturer (brand)
2. Designation of the tread / type of tyre
3. Cross-sectional width in mm
4. Height/width relation in %
5. Radial ply tyre
6. Diameter of the rim in inches
7. Index for the load-bearing capacity
8. Speed index
9. Tubeless
10. Date of manufacture (XX = week, X = year, < = 9th decade)
11. Tread wear indicator (1.6 mm)
12. Additional identifier for tyres with increased load-bearing capacity
13. Notes on the winter suitability of winter and all-season tyres

Source: Reifenfibel, 1.Edizione 1999, Schweiz
Copyright by Bridgestone, Continental, Dunlop, Goodyear, Michelin, Pirelli

The dimension of a tyre

Dimension of the tyre

The technical layout of tyres is specified in § 36 StVZO (German Road Traffic Licensing Regulation). According to this regulation, the tyres of passenger cars are standardised in accordance with the European Directive ECE-R 30. This applies particularly to the labelling on the flank of the tyres. This labelling provides information on the major data of the tyre, including all the important information for the driver of the car. In addition, the standard requires such information as the name of the tyre manufacturer and the type of the tyre.

Tyre width (3)

The width of the tyre is stated in millimetres (e.g. 175 mm). For common passenger car tyres, a cross-sectional width between nominally 125 mm (e.g. 125/80 R 12) and approx. 335 mm (e.g. 335/30 R 19) is sufficient. The values for the cross-sectional width rise in steps of 10 mm. Special tyres for new tyres systems (e.g. TD tyres by Dunlop, or TRX / TDX tyres by Michelin) have other width gauges given in millimetres. The width gauges range from 160 mm to 240 mm. The actual width usually deviates from the nominal width due to production tolerances, and these again differ by some millimetres between different manufacturers. Furthermore it depends on the width of the rim which the tyre is mounted on. The standardisation of tyres makes it possible for most tyres to be mounted on rims of variable widths. These differences might be the cause for the fact that on some vehicles only the tyres of certain manufacturers (brand attachment) or combinations of certain tyres and rims may be used, because only the permitted tyres/combinations guarantee that the tyres can rotate uninhibited in all operational situations (e.g. during deflecting or at full steering angle). The useability of snow chains can also be linked to certain tyre brands and rim widths. Please note the relevant instructions in the car documents and manuals.

Height/width relation / series ....../50, /60, /70, /80 (4)

This value stands for the relation of the height of the tyre to the width of the tyre's cross section in percent. The "/50" statement thus means that the tyre height is half the size of the width of the tyre. Lower relation indexes mean lower flanks – which is the usual appearance of sports cars (225/45...). Exception: In the past, the "/80" statement was not common for tyres of the 80 and 82 series, that's why in older car documents the tyre specification might be given as "155 R 13" which means, if you are buying new tyres, you have to look for "155/80 R 13".

Tyre design (5)

"R" means "radial" here (additionally written out in full in many cases). This is the design common today with radially arranged carcass wires. Diagonal ply tyres used to be the standard until the '60s. Those which are still produced today for special purposes (e.g. vintage cars), are labelled "D" or "-" instead of "R". Note: On principle, mounting tyres of different types (diagonal ply and radial ply) on the same car is not allowed according to StVZO § 36.

Rim diameter (6)

The rim diameter is measured diagonally from one edge of the rim to the other, and given in inches ( " ). The most common sizes range from 10 " to 20 ". Dunlop state the diameters of their TD tyres in millimetres, as do Michelin for their TRX and TDX tyres or their PAX system. The most common diameters range from 315 mm to 440 mm.

Load Index (LI) (7)

This is the index for the load-bearing capacity of the tyre. Each LI value relates to a certain load-bearing capacity of the tyre at a specified tyre pressure – represented in a standardised table. Example: "85" = 515 kg. The mounted tyres have to meet at least the LI given in the car documents, higher values are permissible. Additional entries:

"Speed index" (8)

This index states the permissible maximum speed of the tyre. The letters have the following speed categories assigned to them (shown here: common speed indexes for passenger cars).

GSY      km/h
M        130
N        140
P        150
Q        160
R        170
S        180
T        190
U        200
H        210
V        240
W        270
Y        300
ZR        >240

Specified direction of rotation:

Mostly on tyres with a special profile design, statements such as "Rotation" or "Direction" can be found on the flank in connection with an arrow. This direction of rotation has to be observed when mounting the tyre.

Tubeless (9)

Tyres for passenger cars are usually of the tubeless type. Inserting a tube is not only unnecessary, it is – with few exceptions – not allowed. If in doubt, ask the tyre manufacturer. In case of a flat tyre, inserting a tube is allowed as a temporary makeshift measure.

Date of manufacture (10)

The encoding system up to now: The final three digits of the so-called "DOT" number state the date of manufacture. The two leading digits state the week of production, the final digit states the final digit of the year. Example: 409 = 40th week of 1999. The fact that the '90s are meant, is indicated by a small triangle (on the right-hand side of the three-digit number).

Tread wear indicator ("TWI") (11)

Around the side of the tyre, you will find the token "TWI" (other signs are also possible). If you follow the arrow, you will notice that in this area the profile does not have the full depth. The reason for this: If a tyre is worn down to (the legally permitted) 1.6 mm, these parts of the profile lie clearly visible on the surface; the wear limit is reached. You shouldn't let things get this far: Experiments have shown that below approx. 3 mm, traction – on wet roads in particular – is considerably reduced!

"Reinforced": (12)

This label can be found on tyres with a particularly high load-bearing capacity (for vans, pick-up trucks, off-road vehicles... ). The determining factor is, however, the (appropriately high) LI index.

M&S (winter tyres / all-season tyres) (13)

Winter tyres are marked "M&S", "M+S" or with similar abbreviations. This label clearly indicates that the tyre in question is of a type especially suited for the requirements of the winter season.

Test mark "E":

The "ECE test mark" is represented as an E or e. It confirms the observance of the European standard (ECE- R 30). Fig. 6: The appended "12" indicates Austria as the testing country. Important note: For tyres produced after 1st October 1998 (40th week 98, corresponds to DOT number 408) this labelling on the tyre flank is mandatory in Europe. Consequently, a vehicle may not drive on tyres which – if they were produced after 1st October 1998 – do not bear this test mark. In the course of the general inspection ("TÜV"), the missing of this mark is qualified as a "grave deficiency" in the vehicle.

Retreaded tyres:

Retreaded tyres bear are marked "R", "retread" or "retreaded". The date of retreading is stated in the same way as the date of manufacture on new tyres.