Tire size calculator.
Bigger wheels, done right.
Enter the size on your sidewall and the wheel you want. Get the tire sizes that keep your speedometer honest, or compare any two sizes.
Practically the same height as your tires now, the same width. At 60 mph your speedometer is off by 0.2 mph.
| Tire size for 20" wheels | Overall | vs. now | Width | Speedo at 60 |
|---|---|---|---|---|
| 265/55R20Best match | 31.5" | -0.4% | same | 59.8 mph |
| 245/60R20 | 31.6" | -0.1% | -0.79" | 59.9 mph |
| 295/50R20 | 31.6" | +0.0% | +1.18" | 60.0 mph |
How plus sizing works
A bigger wheel looks better because it fills the arch, but the whole wheel and tire still has to stay about the same height. So as the wheel grows, the sidewall gets lower. Moving from a 17" to a 20" wheel on a truck that runs 265/70R17 usually means a 275/55R20: almost the same height, three more inches of wheel.
Questions
What tire size do I need for bigger wheels?
One that keeps the overall diameter of the wheel and tire close to what you have now, within about 3%. A bigger wheel needs a lower sidewall to stay the same height. Enter your current size and the new wheel diameter above and the calculator lists the sizes that fit that rule.
Why does the 3% rule matter?
Your speedometer, odometer, ABS and traction control are calibrated to the original tire height. Within about 3% they stay accurate. Beyond that the speedometer drifts, and on many vehicles the tire can rub or the systems need recalibration.
How do I read a tire size like 265/70R17?
265 is the tire's width in millimeters, 70 is the sidewall height as a percentage of that width, R means radial, and 17 is the wheel diameter in inches. Flotation sizes like 33x12.50R20 give the overall diameter (33 inches), the width (12.5 inches) and the wheel (20 inches).
Does a bigger tire lift my truck?
A taller tire raises ground clearance by half the difference in overall diameter. Going from a 31.6 inch to a 33 inch tire adds about 0.7 inches at the axle. It also changes your speedometer reading, which the comparison above shows.
Will a lower sidewall ride rougher?
Usually yes. A shorter sidewall flexes less, so the ride is firmer and the wheel is more exposed to potholes. In exchange, steering feels sharper and the bigger wheel fills the arch.