View Here : What Does Tire Size Numbers Mean
Tire Width. Is the width of the tire measured in millimeters from sidewall to sidewall. The first three-digit number in the tire size refers to the tire width. For instance, in a size P215/65 R15 tire, the width is 215 millimeters.
The tire size "P225/45R17 91V" may not mean much to the average person, but to tire geeks like us it speaks volumes. Read on to learn how to crack the tire code with this handy guide dedicated to tire types, sizes, and construction.
The measurement is the tire's section height, and also referred to as the tire's series, profile or aspect ratio. The higher the number, the taller the sidewall; the lower the number, the lower the sidewall. We know that this tire size's section width is 225mm and that its section height is 50% of 225mm.
North America. Tire size was again specified by width in inches and diameter in inches. To differentiate from the earlier 90-ratio tires, the decimal point is usually omitted from the width - for example 685-15 for a tire 6.85 inches wide. Starting in 1972 tires were specified by load rating, using a letter code.
225 identifies the tire section width, which is the measurement of the tire from sidewall to sidewall in millimeters. This measurement varies depending on the rim to which it is fitted. (There are 25.4 millimeters per 1 inch.) 50 is the two-figure aspect ratio.
Understanding Three Numbers in Tire Sizes. The first number in a tire size, say 225, is the width of the tire in millimeters. This is pretty straight forward except that in the days of buying tires sized by the inch (remember 31/10.50x15), the first number was the height rather than the width. Back then it was inches, not millimeters.