TIRES 101: Making Some Sense of Metric and American Standard Tire Sizing (2024)

FAQs

What is the difference between metric and standard tire size? ›

Metric tire sizes are widely used around the world while standard sizes are more commonly used in the United States. Metric tire sizes consist of three main measurements: tire width, aspect ratio, and rim diameter. An example of this would be 245/40R18 for instance.

Start by converting the section width from inches to millimeters. To do this, multiply the section width (in inches) by 25.4 (the number of millimeters in an inch). Next, determine the sidewall measurement, which is the tire diameter minus the wheel size, divided by two.

The two-digit number after the slash mark in a tire size is the aspect ratio. For example, in a size P215/65 R15 tire, the 65 means that the height is equal to 65% of the tire's width. The bigger the aspect ratio, the bigger the tire's sidewall will be.

On metric studs, the thread pitch is the distance in milimeters between each thread. On standard lug nuts, the thread pitch is the number of threads per inch. For example, a 12mmx1. 25 lug nut has a 12mm diameter, and a thread pitch of 1.25mm.

One reason for using different tyre sizes is to improve the car's handling characteristics. By using wider tyres at the rear, the car can have more grip and stability when accelerating and cornering. This setup can also help to reduce understeer, which is when the front tyres lose grip before the rear tyres.

If you mean a 32″ TALL tire simply multiply. 32x25. 4=812.8mm tall.

A: The 295/60R20 is only 11.62 wide and 33.94 tall. The 295 will also hold more weight. The 35 has a maximum load of 3195 and the 295 has a maximum load of 3750.

As a general rule, you want replacement tires that are within 3 percent of the diameter (height) measurement of your existing tires' diameter — assuming your current tires are what your owner's manual recommends.

Yes, these tires should fit just fine. The only difference is that the 265 series tires will be about 10mm shorter in width across the tread in comparison to the 275 series tires. The side wall will also be marginally taller on the 265 series tires.

Choosing tire size wisely

Secondly, to ensure the accuracy of speed data through the car's computer, it's important to look at tire diameter. A good rule of thumb is to stay within a 3% diameter change (3/4 inch diameter change), though pick-ups and SUVs can often handle up to a 15% oversize tire.

Can you use 225 tires instead of 235? ›

Yes you could but it would reduce the overall diameter of the wheel and tyre, so the height would be slightly less, as would the tread width.

Find the information in your vehicle owner's manual in the glove compartment or on the tire information sticker on your driver's side door. Usually those elements contain all the information related to your tire size and specifications as well as the appropriate tire pressure.

After tire width, you'll find a slash and a two digit number. This indicates the aspect ratio, which gives the tire height. Aspect ratio specifically is the tire sidewall height as a percentage of the width. A high aspect ratio means that a tire has a larger sidewall while a lower one means a lower sidewall.

It's highly recommended to use the exact tire size recommended for your car. However, in a pinch the tire width and aspect ratio can be changed slightly and still fit on your rim. Although this will still work, keep in mind it may have adverse effects on the performance of your car.

Metric tire sizes are listed with the width first, then the sidewall height (shown as a percentage of the tire width), [usually] followed by an “R” to designate radial construction, and lastly the wheel/rim size.