245/45R18 vs 235/50R18
235/50R18 is taller than 245/45R18 by 2.14% — a diameter difference of 0.57″.
What changes between 245/45R18 and 235/50R18
Switching from 245/45R18 to 235/50R18 changes overall diameter by +2.14%, a taller tire by 0.57 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″ (245mm → 235mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.29″: 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 66.4 mph. Both sizes share the same 18″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 245/45R18 | 235/50R18 |
|---|---|---|
| Overall diameter | 26.68″ | 27.25″ |
| Section width | 9.65″ (245 mm) | 9.25″ (235 mm) |
| Sidewall height | 4.34″ (45%) | 4.63″ (50%) |
| Rim diameter | 18″ | 18″ |
| Circumference | 83.82″ | 85.61″ |
| Revs per mile | 756 | 740 |
Interactive comparison
275/65R18 or "33" for inch aliases245/45R18
- Diameter
- 26.68″ / 677.7mm
- Section Width
- 9.65″
- Sidewall
- 4.34″ / 110.25mm
- Circumference
- 83.82″
- Revs/Mile
- 756
235/50R18
- Diameter
- 27.25″ / 692.2mm
- Section Width
- 9.25″
- Sidewall
- 4.63″ / 117.5mm
- Circumference
- 85.61″
- Revs/Mile
- 740
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 61.28 mph (98.63 km/h). Your speedometer reads 2.14% low versus actual speed.