Tire code
Automobile tires are described bu an alphanumeric code which is generally molded into the side-wall of the tire.
The meaning of tire codes
The tire code consists of a number of letters and numbers, as follows:
- An optional letter indicating the intended use for the tire (eg 'P' for 'Passenger vehicle').
- The width of the tire - in millimeters.
- A slash character ('/').
- The relation of the side-wall height to the total width of the tire - as a percentage. If this is missing, it is assumed to be 82%
- Construction of the fabric of the tire ('D' - diagonal or 'R' - radial)
- Diameter of the rim that this tire is designed to fit - in inches
- Load index.
- Speed rating - one or perhaps two letterd (see table below)
- Additional marks
Speed rating codes
The code is made up of one or two letters describing the maximum safe speed for the tire.
| Code | MPH | km/h |
|---|---|---|
| N | 93 | 150 |
| Q | 99 | 160 |
| R | 105 | 170 |
| S | 112 | 180 |
| T | 118 | 190 |
| U | 124 | 200 |
| H | 130 | 210 |
| V | 149 | 240 |
| W | 167 | 270 |
| Y | 186 | 300 |
| ZR | Over 149 | Over 240 |
The code "ZR" are means a speed limit for the tire of more than 240 km/h. In this case there is often an additional code, example: 225/45 ZR 17 Y.
On winter tires, at the end of the above mentioned codes the following abbreviation can be found: M&S for Mud and Snow. On spike tires there is an additional E after the S.
Additional marks
- E4
- Tire approved according ECE-regulations, 4 = Country of approval
- 030908
- Approval number of the tire
- DOT-Nummer
- Production date; DOT = Department of Transportation; example: DOT 3204 = 32nd week in 2004; before 2000 there was a 3 number code with triangle-symbol used, Example: 122? = 12th week of 1992; prior this the following code was used: 065 = 6th week of 1985
- Tubeless or TL
- Tubetype or TT, tire with a tube
- Made in
- Country of production
- C (commercial)
- Tires for light lorries (Example: 185 R14 C)
- B
- Bias Belted tires for motorcycles (Example: 150/70 B 17 69 H)=diagonal construction with belt added under the tread
- SFI
- abbr. for "side facing inwards" = inside of asymmetrically tires
- SFO
- abbr. for "side facing outwards" = outside of asymmetrically tires
- TWI
- Tire wear index, an indicator in the main tire profile which shows when the tire is worn down and needs to be replaced
- XL (extra load)
- Tire for heavy loads
- rf
- Reinforced tires
Example
185/65 R 15 85 H
- 185 the total width is 185 mm, on the widest part of the tire, i.e. approx at mid flank height
- 65 is the relation of flank height to width, here the height is 120 mm (65% of 185 mm).
- R radial fabric construction
- 15 necessary rim diameter in inches.
- 85 load index, here 515 kg.
- H speed index, this means the maximum permitted speed, here 210 km/h.