How to read a tire size
The string of numbers and letters on a tire sidewall looks like a code, but it is a simple description of the tire. Once you can read it, it is much easier to ask for the right replacement, compare quotes and avoid buying something that does not fit your vehicle.
Breaking down 275/65R18
- 275 is the section width: how wide the tire is, measured in millimeters.
- 65 is the aspect ratio: the height of the sidewall as a percentage of that width. A lower number means a shorter sidewall.
- R means radial construction, which is how nearly all modern car and light truck tires are built.
- 18 is the wheel diameter in inches: the size of the wheel the tire is made to fit.
All four parts have to match what your vehicle calls for. Changing any of them changes how the tire fits the wheel and the vehicle.
Letters in front: P and LT
Some sizes start with a letter. P indicates a passenger tire and LT indicates a light truck tire. Even when the numbers after the letter are the same, the two types are built differently and are not interchangeable by default. Light truck tires are made for heavier loads and towing, and a vehicle that came with them generally needs them again. If your current tires have a letter in front of the size, include it when you ask for a quote.
Load index and speed rating
Right after the size you will usually find a number and a letter. The number is the load index, which describes how much weight the tire is built to carry, and the letter is the speed rating. Both matter for safety. Replacement tires should generally meet what the vehicle maker specifies, so read these off your current tires or the placard before you shop.
Where to find the right size
There are two reliable places to look. The first is the sidewall of the tires on your vehicle now, as long as they are the original size. The second is the placard on the driver-door jamb, which lists the size the vehicle maker fitted, along with the recommended pressures. The owner's manual has the same information.
If the tires on the car do not match the placard, or you are simply not sure, call the shop and we will check it with you. It helps to have the full size, including any letters in front and the load index and speed rating after it.
Any size can be sourced
If the size you need is not on our racks, we can source it from nearby warehouses, usually the same day. Prices are quoted by phone, so you can compare before you decide. You can also search our current stock by size online.
Size pages: 265/70R17 · 245/70R19 · 225/55R17 · 215/65R15 · 225/65R17 · 215/60R16 · 225/50R18 · 245/40R20