225/55R18 vs 235/55R18 at a glance
| Measure | 225/55R18 (current) | 235/55R18 (new) | Difference |
|---|---|---|---|
| Overall height | 27.74 in | 28.18 in | +0.43 in (+1.56%) |
| Width | 8.86 in (225 mm) | 9.25 in (235 mm) | +10 mm |
| Sidewall | 4.87 in | 5.09 in | +0.22 in |
| Wheel | 18 in | 18 in | +0 in |
| Circumference | 87.2 in | 88.5 in | +1.4 in |
| Revs per mile | 726.9 | 715.8 | −11.2 |
Verdict: close match
Within the 3% rule of thumb, so the speedometer, gearing and ride height change little. Going from 225/55R18 to 235/55R18 is a 1.6% increase in overall height (+0.43 in), and the vehicle sits about 0.22 in higher. The tire is 10 mm wider. The 3% rule of thumb comes from Discount Tire and 1010tires; it is not a guarantee of fit.
True speed and odometer
| Speedometer shows | You are really doing | Difference |
|---|---|---|
| 35 mph | 35.5 mph | +0.5 mph |
| 45 mph | 45.7 mph | +0.7 mph |
| 55 mph | 55.9 mph | +0.9 mph |
| 60 mph | 60.9 mph | +0.9 mph |
| 65 mph | 66.0 mph | +1.0 mph |
| 70 mph | 71.1 mph | +1.1 mph |
| 75 mph | 76.2 mph | +1.2 mph |
Odometer: 1,000 indicated miles is 1,016 real miles, and 10,000 is 10,156.
The math
225/55R18: 18 + 2 × (225 × 55% ÷ 25.4) = 27.74 in. 235/55R18: 18 + 2 × (235 × 55% ÷ 25.4) = 28.18 in. Change = 28.18 ÷ 27.74 − 1 = +1.56%. True speed at 60 = 60 × 28.18 ÷ 27.74 = 60.94 mph.
Check next
- Regear and RPM at cruise for this swap
- Speedometer and odometer correction
- Other sizes within ±3% of 225/55R18
Calculated from the size alone. Real tires vary a little by brand and model, and the loaded radius is a bit smaller. Confirm the wheel width range, clearance, load index and speed rating for your vehicle. See how to read a tire size, the load index chart and the speed rating chart.
Size pages: 225/55R18 · 235/55R18. More swaps: all tire size comparisons.