Tire to Rim Fitment Guide
Whenever you fit tires to your car rims, it is important to consider several measurements. Tire sizes include the width in millimeters of the tire tread, the sidewall aspect ratio and the diameter of the wheel. It is also important to pick a tire with an appropriate speed rating. Picking the appropriate tire for your car's rims can improve handling and performance, safety, gas mileage and tire wear.
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Width of Tire
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The first measurement of a tire is its width. Tire width is the distance between the left and right sidewall of the tire and is measured in millimeters. A car rim can accommodate a small range of tire widths. Generally speaking, as tire width increases, performance and handling will increase. Wider tires also cost more and slightly reduce fuel efficiency, since there is increased contact with the road.
Tire Sidewall
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The second part of a tire measurement is the ratio of sidewall to tire width. This number is written as the percentage of the tire's width. In other words, if the sidewall ratio was 50, then the height of the sidewall is 50 percent of the width of the tire. While tire widths are measured in millimeters, sidewalls are measured in inches. Shorter sidewalls improve the handling of a car but increase the likelihood of rim damage.
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Diameter
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Diameter is the third part of a tire's measurement. The diameter of the rim must always match the diameter of the tire. This measurement usually ranges from 14 to 18 inches, but it can be more or less depending on the car and whether or not the wheel is an aftermarket rim. Generally, the greater the diameter, the better the handling and the heftier the price tag.
How to Write a Tire Measurement
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A tire that has a tread width of 225 mm, a sidewall ratio of 50, and a diameter of 17 is written as 225/50/17. Every tire has this information on its sidewall and most cars will have the recommended tire size in the door jamb and manufacturer's manual.
Speed Rating
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The final component of fitment is speed rating. Although the speed rating of a tire does not change its size, it can make it unsuitable for your vehicle. It is recommended to purchase tires with a speed rating that equals or exceeds the maximum speed of your car. Failure to do so can result in tire damage at high speeds. Higher speed ratings may cost more than lower ones.
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References
- Photo Credit line of tires image by ashotoflife from Fotolia.com
