255/45R20 Tires & Tire Size

255/45R20 refers to the size of the tire. It’s a standard which is used by car and tire manufacturers. By having the standard, tire manufacturers are able to manufacture same size tires independently and users can buy same size tires from different manufacturers.

Here’s an explanation of what these metrics mean in practice:

255	The tire width is 255mm.
45	The aspect ratio of the tire is 45. Aspect ratio refers to the height of tire sidewall in relation to tire width in percentages.
R	The letter in the middle refers to tire construction. Practically all tires sold for cars are radials. Sometimes you also see tires with RF or ZR. RF indicates the tire is run flat, whereas ZR means the tire has speed rating higher than V. These tires are also radials, as the R indicates.
20	Rim diameter for the tire. 255/45R20 tire can be mounted only to a 20″ rims.

What is 255/45R20 tire size in inches?

Because the width of 255/45R20 tire is stated in millimeters and sidewall height in percentages, you have to make calculations to see what the true size of 255/45R20 is in inches. Luckily, we have made these calculations for you.In this table you can see size of 255/45R20 in inches, as well as few additional metrics:

	In inches	In millimeters
Section Width	10.0″	255mm
Sidewall height	4.5″	115mm
Diameter / Height	29.0″	738mm
Circumference	91.2″	2317mm
Rim Diameter	20″
Revolutions	695 per mile	432 per kilometer

Recommended Rim Sizes for 255/45R20 Tires

For 255/45R20 tires you need to have correct size rims to install the tires to. There are different width rims available in the market, and you can run into problems by installing 255/45R20 to a too wide or too narrow rim. Here are the recommended rim sizes for 255/45R20 tire:

Diameter	Width Range
20″	8-9.5″

255/45R20 – Variations

When you look at the tire code on 255/45R20 tires, you may see there are additional numbers and letters after the code 255/45R20. These numbers and letters refer to speed rating and load index of the tire. 255/45R20 has at least following variations available on the markets: