Find the Right Size Tire for My Car

Look at the sidewall of any tire on the vehicle. You will see a code such as 245/65R17. That is your size: 245mm section width, 65 aspect ratio, radial construction, 17-inch rim. Confirm it against the placard on your driver's door jamb, which lists the size the manufacturer specified from the factory.

Start with the OEM size on your door placard. That size is guaranteed to fit and delivers the handling, load capacity, and speedometer accuracy the manufacturer engineered. Alternative sizes may fit, but changing width, aspect ratio, or diameter affects speedometer calibration, load capacity, and clearance, so verify any alternative with a tire professional first.

Driving creates friction, friction creates heat, and heat raises the pressure inside the tire. A tire checked right after driving reads higher than its true cold pressure, and setting pressure from that reading leaves you underinflated once it cools. Three hours parked, or before you drive in the morning, gives an accurate cold reading.

On most vehicles yes, but some performance cars use a staggered fitment with wider tires on the rear. Check the placard carefully, because it lists front and rear sizes separately when they differ. It may also list different recommended pressures front to rear based on weight distribution.

Speedometer and odometer readings become inaccurate, which affects your fuel economy math and your warranty mileage records. Load capacity may be insufficient for the vehicle's weight. Clearance problems can cause rubbing under full steering lock or suspension compression. Stability control and ABS calibration can also be affected.