225/55R18 vs 235/55R18
235/55R18 is taller than 225/55R18 by 1.56% — a diameter difference of 0.44″.
What changes between 225/55R18 and 235/55R18
Switching from 225/55R18 to 235/55R18 changes overall diameter by +1.56%, a taller tire by 0.44 inches. This lands inside the ±3% fitment safe zone, so most vehicles will accept the swap without rubbing, speedometer recalibration, or ABS/TPMS complications. Section width moves by +0.39″ (225mm → 235mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.22″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -11, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 66.0 mph. Both sizes share the same 18″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 225/55R18 | 235/55R18 |
|---|---|---|
| Overall diameter | 27.74″ | 28.18″ |
| Section width | 8.86″ (225 mm) | 9.25″ (235 mm) |
| Sidewall height | 4.87″ (55%) | 5.09″ (55%) |
| Rim diameter | 18″ | 18″ |
| Circumference | 87.16″ | 88.52″ |
| Revs per mile | 727 | 716 |
Interactive comparison
275/65R18 or "33" for inch aliases225/55R18
- Diameter
- 27.74″ / 704.7mm
- Section Width
- 8.86″
- Sidewall
- 4.87″ / 123.75mm
- Circumference
- 87.16″
- Revs/Mile
- 727
235/55R18
- Diameter
- 28.18″ / 715.7mm
- Section Width
- 9.25″
- Sidewall
- 5.09″ / 129.25mm
- Circumference
- 88.52″
- Revs/Mile
- 716
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 60.94 mph (98.07 km/h). Your speedometer reads 1.56% low versus actual speed.