235/65R16 vs 225/55R18
225/55R18 is 0.28 in (7.2 mm) shorter than 235/65R16, a −1.01% diameter difference. With the speedometer set for 235/65R16, an indicated 60 mph is 59.4 mph on 225/55R18.
Is this a safe swap?
Diameter difference −1.01%: within the ±3% guideline
By overall diameter alone, 225/55R18 falls inside the ±3% range commonly used as a guideline when replacing 235/65R16. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.
| Measurement | 235/65R16 | 225/55R18 | Difference | % diff |
|---|---|---|---|---|
| Overall diameter | 28.03 in (711.9 mm) | 27.74 in (704.7 mm) | −0.28 in (−7.2 mm) | −1.01% |
| Sidewall height | 6.01 in (152.8 mm) | 4.87 in (123.8 mm) | −1.14 in (−29.0 mm) | −18.99% |
| Section width | 9.25 in (235.0 mm) | 8.86 in (225.0 mm) | −0.39 in (−10.0 mm) | −4.26% |
| Circumference | 88.05 in (2,236.5 mm) | 87.16 in (2,213.9 mm) | −0.89 in (−22.6 mm) | −1.01% |
| Revolutions per mile | 720 | 727 | +7 | +1.02% |
| Indicated | Actual on 235/65R16 | Actual on 225/55R18 | Difference |
|---|---|---|---|
| 30 mph | 30.0 mph | 29.7 mph | −0.3 mph |
| 60 mph | 60.0 mph | 59.4 mph | −0.6 mph |
| 75 mph | 75.0 mph | 74.2 mph | −0.8 mph |
Ride-height change: 225/55R18 lowers the vehicle by 0.14 in (3.6 mm) at the axle (half the −7.2 mm diameter difference).
225/55R18 is 0.28 in shorter than 235/65R16 and 10 mm narrower, a 1.01% difference in overall diameter.
With the speedometer calibrated for 235/65R16, an indicated 60 mph is actually 59.4 mph on 225/55R18, and revolutions per mile change from 720 to 727.
225/55R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 235/65R16.
Size pages
Other comparisons with 235/65R16
- 225/75R14 vs 235/65R16
- 215/75R15 vs 235/65R16
- 235/70R15 vs 235/65R16
- 225/75R15 vs 235/65R16
- 215/65R16 vs 235/65R16
- 235/60R16 vs 235/65R16
- 225/65R16 vs 235/65R16
- 215/70R16 vs 235/65R16
Other comparisons with 225/55R18
- 225/65R16 vs 225/55R18
- 245/60R16 vs 225/55R18
- 215/70R16 vs 225/55R18
- 205/75R16 vs 225/55R18
- 245/55R17 vs 225/55R18
- 225/60R17 vs 225/55R18
- 215/65R17 vs 225/55R18
- 225/50R18 vs 225/55R18
Source: Calculated from standard tire geometry formulas. Verified . How these numbers are calculated.