Your tire is the only thing touching the road. Here is how to read a size and pick the right one for your build.
Reading a tire size
245/40R18 97Y
- 245: section width in millimeters
- 40: aspect ratio, the sidewall is 40% of the width (98 mm here)
- R: radial construction
- 18: fits an 18 inch wheel
- 97: load index, the weight each tire can carry
- Y: speed rating (Y = 186 mph, W = 168, V = 149, H = 130)
Keep the overall diameter close to stock
When you go up in wheel size, the sidewall has to get shorter so the whole tire stays the same height. Stay within about 3% of the factory overall diameter. Bigger than that and your speedometer reads wrong, ABS and stability control can act up, and the tire can hit the fender or suspension. Example: a factory 235/35R19 (25.5 in tall) becomes 235/40R18 on an 18 inch wheel or 245/30R20 on a 20.
Match tire width to wheel width
- 7 to 7.5 inch wheel: 215 to 225 tires
- 8 to 8.5 inch wheel: 225 to 245 tires
- 9 to 9.5 inch wheel: 245 to 265 tires
- 10 to 10.5 inch wheel: 265 to 285 tires
- 11 inch and up: 285 to 305 tires
A slightly narrower tire on a wide wheel gives a stretched look. A little stretch is common in stance builds. Big stretch is not something we recommend for street driving.
Which type?
- Summer / max performance: the most grip in warm weather. Not for snow or near-freezing temps.
- All-season UHP: strong grip with year-round use in mild climates.
- All-weather: carries the snowflake rating for real winter use while staying usable in summer.
- Track / 200 treadwear: autocross and track days. Wears fast on the street.
Staggered tires
If your car runs wider rear wheels, the rear tires are a different size than the fronts. Buy them as a set of two front and two rear. Our Tires by Vehicle tool lists both axles for every wheel diameter.