What Size Tire Does My Car Need?
Your car needs the correct tire size. Tire size is important for your cars handling and performance. But, it also helps keep you safe.
Cars and Trucks are designed so that all critical components work together. Our experts say the most crucial part of your car are the tires since they are the only part of your vehicle actually touch the road. Tires impact car handling, acceleration, braking forces, and overall car safety.
You need to know how to decode the digits…
The sidewall of a car tire informs you a lot about its size and characteristics, including its age and intended uses. This is in addition to the brand name and model of your vehicle's tire.
There are some basics to help you understand your tires code. First you need to find the size designation, which will look something like this: 245/50-25R. The first three numbers state the width of the tire in millimeters, from outer sidewall to inner sidewall (to get the measurement of your tire in inches, divide by 25.4).
The next two numbers (after the slash mark) inform you of the the height of the tires sidewall. This measurement is from the rim to tire tread. This is listed as a percentage (50% in the above case) of the width. This percentage is known as the tire aspect ratio. This is sometimes referred to as the tire's “profile,” and can also be called the “section.”
The hyphen "-" that follows the aspect ratio, the next two numbers, describe the wheel diameter that the tire can mount to. This is noted in inches. In our example this tire is for a 25-inch wheel. (Yes that is a massive wheel.) The “R” after the 25 in our example above means that the tire is a radial tire.
While you can sometimes find belted tires for trucks (designated B) and bias-ply tires for older vehicles (with a D, for the diagonal orientation of the belt), most tires will be radials.
More details can be found online here are the National Highway Traffic Safety Administration’s advice by CLICKING HERE.
The accuracy of your car’s speedometer is also impacted by tire size. Car speedometers are connected to the car’s transmission. It is calibrated based on the revolution of the manufacture’s recommended tire size. A shorter or taller tire will cause readings to be inflated or deflated (forgive the tire pun). Some people will choose to change their vehicle’s wheel diameter due to appearance or performance reasons. Your new tires should account for the fact that you have adjusted one aspect of your tire size. bThat is to say that the total diameter and circumference of your tire should stay the same. So a lower profile tire will require a larger wheel (or rim) to maintain the same total diameter of the tire and wheel together.
You can check your owner’s manual for more specific information on your tires or contact us at Ace Car Care Center if you still have questions. Our Tire Experts are always here to help.