Tire Calculator

A tire size calculator can be used for comparing various tires. Because there are many different specs available, knowing how to use these will come in handy. These are available for free on the Internet.

Ways of Using the Calculators

You start by choosing the vehicle stock tire. You can specify the car and the year (example, Acura 2008) or you can choose the tread width, the profile and diameter. Some calculators have additional sizes for you to choose from.

To compare the tire you can select from the various specs listed on the site. Once you make your selection, the results will appear automatically.

How to Determine the Tire Specs

You can use a tire calculator only if you know the facts about your tires. Here is what you need to know.

Service Type

The letter at the beginning of the tire signifies its purpose. The letter P means the tire is for mini vans, cars, light pickups, sports utility vehicles and other passenger vehicles. If the tire says P225/50R16 91S, it is for passenger vehicles.

If the letter is a T, it is a temporary spare. LT means it is for trucks carrying large cargo. If the letters are ST, it is a special trailer service tire utilized for trailers. They are not to be used on cars.

What is the Section Width?

Sometimes a tire calculator will require you to input the section width. This is the cross section of the tire indicated in mm. A P225/50R16 91S tire measures 225 mm from the outer to the inner sidewall.

Sidewall Aspect Ratio

Next to the section width is the aspect ratio, for example, P225/50R16 91S. The 50 after the 225 means the tire is 50 percent higher than the measured section width. The height is measured from rim to the tread.

Note: you cannot just rely on a tire calculator if you want to change the size. It is best to consult a professional or the dealer you bought the vehicle from to get the best fit.

The Internal Construction

This is the R in the P225/50R16 91S. R means radial tires and is in 98% of all tires used. If the letter is D, it means the tire plates have a bias ply configuration.

Wheel and Tire Diameter

The 16 after the R refers to the tire and wheel diameter. Other sizes are 8, 10, 12, 13, 14, 15, 17, 18, 19, 20, 22, 23, 24, 26 and 28. These are known as inch rim. They are utilized in SUVs, light trucks, cars and vans. There are other kinds of tire/wheel diameters used, but the inch rims are the most common.

Warning: it is crucial that the tire and wheels are correctly matched prior to mounting.

Service Description

This would be the 91S. It refers to the load index and speed rating.

Using a tire calculator helps you get insights into how well a tire can fit. However, be certain the data input is correct so you can get an accurate result.