Key to Tire Designation Codes

Speed Rating

Sustained speed rating is designated by a letter code: N 93 mph (150 km/h) S 112 mph (180 km/h) H 130 mph (210 km/h) V 149 mph (240 km/h) Z 149+ mph (240+ km/h)

Tire Size

Wheel diameters are usually in inches and tire width in millimeters or a letter designation.

Tire Widths

mm letter inches 80 MH 3.00 90 MJ 3.25 100 ML 3.50 110 MM 4.00 120 MP 4.50 130 MT 5.00 140 MU 5.50 150 MV 6.00

Shoulder Heights

The shoulder height is stated as a percentage of the tire width as in the following tire designation.


Where the 100 is tire width in mm. The 90 means the shoulder height is 90 mm or 90 percent of 100. It is a V speed rated or 149 mph. And fits a 18 inch wheel.

D.O.T. Number

The tire also contains a D.O.T. number. The last three digits show the year and week that the tire was manufactured. e.g., a tire stamped 324 means the tire was made in the 32nd week of 1994. Hopefully, it will not be too difficult to tell the difference in a tire made in 1984 from one made in 1994. Tires suffer from sunlight, ozone, and aging deterioration. You should choose the newer tire when the opportunity exists.

Source for decoding where the tire was manufactured

Addendum from "Craig" <hcat7@3lefties.com>

The place to see all manufacturing sites for DOT approved tires is at the following site:

At the top of the page will be a search box and above that is an alphabet list. Just select the first letter that follows the DOT stamp on your tire. My Michelins are HB. Shows to be made in Spain. (tires in the rain are mainly made in Spain) (sorry) My old .... Avons are AT and are of English ilk. Enjoy!

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Last Update: Monday, December 04, 2000