P-Metric sizing is the standard sizing used today. The size is preceded by a letter indicating usage such as P = passenger, ST = Special Trailer, or LT = Light Truck and then followed by three sets of numbers. The size will be express be as tread width in MM, a forward slash and then Aspect ratio (sidewall height as a percentage of tread width), another letter such as R=Radial or D= bias and then the final number in the size is rim diameter in inches.
Metric non-series sizes are not preceded by a letter indicating usage. They also do not include the aspect ratio. Just width in MM and rim diameter in inches.
Alpha-numeric sizing was used in the 1960's thru 1970's. It was phased out and replaced by the P-metric system used today as all modern passenger tires went to radial construction.
The size contains only numbers. This method was used only on bias tires and preceded the use of Alpha-numeric sizing.
To use the search box below enter the NUMBERS ONLY of your tire size in order in the search box WITHOUT any punctuation.
Examples:
P235/75R15 you would enter 2357515
20X10.00-8 you would enter 2010008
5.50-16 you would enter 55016
18.4R38 you would enter 18438
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