235/50R18 vs 245/50R18
245/50R18 is taller than 235/50R18 by 1.44% — a diameter difference of 0.40″.
What changes between 235/50R18 and 245/50R18
Switching from 235/50R18 to 245/50R18 changes overall diameter by +1.44%, a taller tire by 0.40 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 +0.40″ (235mm → 245mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.19″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -10, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 65.9 mph. Both sizes share the same 18″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 235/50R18 | 245/50R18 |
|---|---|---|
| Overall diameter | 27.25″ | 27.65″ |
| Section width | 9.25″ (235 mm) | 9.65″ (245 mm) |
| Sidewall height | 4.63″ (50%) | 4.82″ (50%) |
| Rim diameter | 18″ | 18″ |
| Circumference | 85.61″ | 86.85″ |
| Revs per mile | 740 | 730 |
Interactive comparison
275/65R18 or "33" for inch aliases235/50R18
- Diameter
- 27.25″ / 692.2mm
- Section Width
- 9.25″
- Sidewall
- 4.63″ / 117.5mm
- Circumference
- 85.61″
- Revs/Mile
- 740
245/50R18
- Diameter
- 27.65″ / 702.2mm
- Section Width
- 9.65″
- Sidewall
- 4.82″ / 122.5mm
- Circumference
- 86.85″
- Revs/Mile
- 730
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 60.87 mph (97.96 km/h). Your speedometer reads 1.44% low versus actual speed.