How to Tell Whether Tires Will Fit on Rims

by Contributor

If you're changing tires, you should first tell whether the new models will fit on the rims of your car. Or if you're upgrading your rims, you want to make sure that the tires will fit. Obtaining the metrics you need to make these determinations is easy.

Measure the rims. You're looking for overall diameter, width and offset. Measure with a tape measure for precise results. Rim width is measured between the flanges (the part which the bead of the tire touches). Be sure to measure it from those specification. If you have an owner's manual for your vehicle, that should contain the information and you can save time by skipping this measurement.

Determine whether the new tires you want will fit your vehicle and whether they are appropriate for the kind of driving you do. Check the tire's code (the string of letters and/or numbers written on the side). The first letter indicates what type of vehicle they are for. "P" for passenger vehicles, "LT" for light truck and "T" for a spare tire.

Check the inter-hole diameter of your tires and make sure it conforms to the diameter of the rims. You can't put a 15-inch tire on a 16-inch rim or a 17-inch tire on a 15-inch rim.

Get the tire's rim width recommendations. Tires have fairly flexible sidewalls, which will allow them to fit a fair range of rim widths. Make sure your tires fit within the range of your rim's width.

Subtract the diameter of your rims from the overall diameter of the tires currently on the rims (from tread-mark to tread-mark) and divide the result by 2. The result is your tire's sidewall height. You can also get this figure by multiplying the tire's listed width (the first 3 numbers on its code after the letter, measured in mm) times the tire's listed sidewall height percentage (the numbers after the slash on its code: the percentage of its width).

Compare the tire's sidewall height to the sidewall height of the new tires. They should be as close to each other as possible.

Tip

  • check Tires are usually measured in mm, which the numbers on the code represent. If you're comparing such numbers to measurements you make with a ruler, you will probably need to convert the figures into universal terms (inches to mm or mm to inches). 1 inch equals 25.4 mm.

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