255/45R22 vs 315/40R21 tire size comparison
315/40R21 is 0.1 in (0.37%) shorter than 255/45R22 and 2.4 in wider. They fit different wheels: 255/45R22 a 22-inch wheel and 315/40R21 a 21-inch wheel.
255/45R22 and 315/40R21 side by side
| Measurement | 255/45R22 | 315/40R21 | Difference | Difference % |
|---|---|---|---|---|
| Section width | 10.0 in (255 mm) | 12.4 in (315 mm) | +2.4 in (+60 mm) | +23.53% |
| Sidewall height | 4.5 in (115 mm) | 5.0 in (126 mm) | +0.5 in (+11 mm) | +9.80% |
| Wheel (rim) diameter | 22.0 in (559 mm) | 21.0 in (533 mm) | -1.0 in (-26 mm) | -4.55% |
| Overall diameter | 31.0 in (788 mm) | 30.9 in (785 mm) | -0.1 in (-3 mm) | -0.37% |
| Circumference | 97.5 in (2477 mm) | 97.1 in (2467 mm) | -0.4 in (-10 mm) | -0.37% |
| Revolutions per mile | 650 | 652 | +2 | +0.37% |
Differences are 315/40R21 minus 255/45R22; percentages are relative to 255/45R22. These are nominal design dimensions. Real tires vary by brand, tread depth, wheel width, load and pressure.
The overall diameter differs by 0.37%, which is within the common 3% rule of thumb.
The rule of thumb keeps a replacement size within about 3% of the original overall diameter. It covers diameter only. It is not a fit, load or safety check, because width, wheel diameter, load capacity and clearance matter too. Confirm any size change with your vehicle's owner's manual or a tire professional.
Speedometer difference
When the speedometer reads 60 mph on a vehicle built for 255/45R22, the actual speed on 315/40R21 is about 59.8 mph. When it reads 60 mph on a vehicle built for 315/40R21, the actual speed on 255/45R22 is about 60.2 mph. These figures assume the speedometer is accurate on the original size and use nominal dimensions, so treat them as estimates.
| Speedometer reads | Actual on 315/40R21 (built for 255/45R22) | Actual on 255/45R22 (built for 315/40R21) |
|---|---|---|
| 20 mph | 19.9 mph | 20.1 mph |
| 30 mph | 29.9 mph | 30.1 mph |
| 40 mph | 39.9 mph | 40.1 mph |
| 50 mph | 49.8 mph | 50.2 mph |
| 60 mph | 59.8 mph | 60.2 mph |
| 70 mph | 69.7 mph | 70.3 mph |
| 80 mph | 79.7 mph | 80.3 mph |
A common rule of thumb is to keep a replacement size within about 3% of the original overall diameter. Check the tire placard on the driver's door jamb and your owner's manual for the sizes your vehicle was built for. Confirm any size change with your vehicle's owner's manual or a tire professional.
Which vehicles use each size?
These vehicles list the size among their verified sizes, by trim. Open one to see all of its sizes.
Check it in the calculator
The calculator takes the same two sizes and shows the full comparison, or lets you swap either one for another size.
Open this comparison in the calculatorShop for 255/45R22 or 315/40R21 tires
Confirm the size on your tire sidewall or door placard first. These links open each store's own search; prices and stock are on their sites.
255/45R22
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Other comparisons with 255/45R22
Side-by-side dimensions and speedometer difference for sizes close to 255/45R22 in overall diameter.
- 255/45R22 vs 255/50R21+0.01% taller than 255/45R22
- 255/45R22 vs 255/55R20+0.03% taller than 255/45R22
- 255/45R22 vs 255/60R19+0.04% taller than 255/45R22
- 255/45R22 vs 255/65R18+0.05% taller than 255/45R22
- 255/45R22 vs 255/70R17+0.06% taller than 255/45R22
Other comparisons with 315/40R21
Side-by-side dimensions and speedometer difference for sizes close to 315/40R21 in overall diameter.
- 275/55R19 vs 315/40R21-0.04% shorter than 315/40R21
- 275/60R18 vs 315/40R21+0.23% taller than 315/40R21
- 275/50R20 vs 315/40R21-0.31% shorter than 315/40R21
- 255/50R21 vs 315/40R21+0.38% taller than 315/40R21
- 255/55R20 vs 315/40R21+0.39% taller than 315/40R21
You might also need
- Digital tire pressure gauge (Amazon search, opens in a new tab)
Check your tire pressure against the number on your door placard.
- Portable tire inflator (Amazon search, opens in a new tab)
Top up a low tire at home without a trip to the gas station.
- Tire tread depth gauge (Amazon search, opens in a new tab)
Measure how much tread is left before you decide to replace.
- Lug wrench or torque wrench (Amazon search, opens in a new tab)
Useful for rotations and tire changes; follow the torque spec in your owner's manual.
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