235/55R18 vs 275/50R18
275/50R18 is taller than 235/55R18 by 2.31% — a diameter difference of 0.65″.
What changes between 235/55R18 and 275/50R18
Switching from 235/55R18 to 275/50R18 changes overall diameter by +2.31%, a taller tire by 0.65 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 +1.58″ (235mm → 275mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.32″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -16, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 66.5 mph. Both sizes share the same 18″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 235/55R18 | 275/50R18 |
|---|---|---|
| Overall diameter | 28.18″ | 28.83″ |
| Section width | 9.25″ (235 mm) | 10.83″ (275 mm) |
| Sidewall height | 5.09″ (55%) | 5.41″ (50%) |
| Rim diameter | 18″ | 18″ |
| Circumference | 88.52″ | 90.56″ |
| Revs per mile | 716 | 700 |
Interactive comparison
275/65R18 or "33" for inch aliases235/55R18
- Diameter
- 28.18″ / 715.7mm
- Section Width
- 9.25″
- Sidewall
- 5.09″ / 129.25mm
- Circumference
- 88.52″
- Revs/Mile
- 716
275/50R18
- Diameter
- 28.83″ / 732.2mm
- Section Width
- 10.83″
- Sidewall
- 5.41″ / 137.5mm
- Circumference
- 90.56″
- Revs/Mile
- 700
Speedometer & Diameter Impact
Wider tire — verify wheel widthAt an indicated 60 mph, your actual speed is 61.38 mph (98.79 km/h). Your speedometer reads 2.31% low versus actual speed.