235/60R17 vs 315/40R18 tire size comparison
315/40R18 is 0.2 in (0.64%) shorter than 235/60R17 and 3.1 in wider. They fit different wheels: 235/60R17 a 17-inch wheel and 315/40R18 an 18-inch wheel.
235/60R17 and 315/40R18 side by side
| Measurement | 235/60R17 | 315/40R18 | Difference | Difference % |
|---|---|---|---|---|
| Section width | 9.3 in (235 mm) | 12.4 in (315 mm) | +3.1 in (+80 mm) | +34.04% |
| Sidewall height | 5.6 in (141 mm) | 5.0 in (126 mm) | -0.6 in (-15 mm) | -10.64% |
| Wheel (rim) diameter | 17.0 in (432 mm) | 18.0 in (457 mm) | +1.0 in (+25 mm) | +5.88% |
| Overall diameter | 28.1 in (714 mm) | 27.9 in (709 mm) | -0.2 in (-5 mm) | -0.64% |
| Circumference | 88.3 in (2242 mm) | 87.7 in (2228 mm) | -0.6 in (-14 mm) | -0.64% |
| Revolutions per mile | 718 | 722 | +4 | +0.65% |
Differences are 315/40R18 minus 235/60R17; percentages are relative to 235/60R17. These are nominal design dimensions. Real tires vary by brand, tread depth, wheel width, load and pressure.
The overall diameter differs by 0.64%, 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 235/60R17, the actual speed on 315/40R18 is about 59.6 mph. When it reads 60 mph on a vehicle built for 315/40R18, the actual speed on 235/60R17 is about 60.4 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 315/40R18 (built for 235/60R17) | Actual on 235/60R17 (built for 315/40R18) |
|---|---|---|
| 20 mph | 19.9 mph | 20.1 mph |
| 30 mph | 29.8 mph | 30.2 mph |
| 40 mph | 39.7 mph | 40.3 mph |
| 50 mph | 49.7 mph | 50.3 mph |
| 60 mph | 59.6 mph | 60.4 mph |
| 70 mph | 69.5 mph | 70.5 mph |
| 80 mph | 79.5 mph | 80.5 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 235/60R17 or 315/40R18 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.
235/60R17
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Other comparisons with 235/60R17
Side-by-side dimensions and speedometer difference for sizes close to 235/60R17 in overall diameter.
- 235/60R17 vs 295/35R20+0.10% taller than 235/60R17
- 235/60R17 vs 255/45R19-0.24% shorter than 235/60R17
- 235/60R17 vs 255/40R20-0.25% shorter than 235/60R17
- 235/55R18 vs 235/60R17+0.27% taller than 235/60R17
- 235/60R17 vs 255/35R21-0.27% shorter than 235/60R17
Other comparisons with 315/40R18
Side-by-side dimensions and speedometer difference for sizes close to 315/40R18 in overall diameter.
- 285/35R20 vs 315/40R18-0.24% shorter than 315/40R18
- 215/70R16 vs 315/40R18-0.25% shorter than 315/40R18
- 215/65R17 vs 315/40R18+0.30% taller than 315/40R18
- 255/35R21 vs 315/40R18+0.38% taller than 315/40R18
- 255/40R20 vs 315/40R18+0.39% taller than 315/40R18
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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