245/50R20 vs 235/55R20
235/55R20 is taller than 245/50R20 by 1.79% — a diameter difference of 0.53″.
What changes between 245/50R20 and 235/55R20
Switching from 245/50R20 to 235/55R20 changes overall diameter by +1.79%, a taller tire by 0.53 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 +0.27″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -12, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 66.2 mph. Both sizes share the same 20″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 245/50R20 | 235/55R20 |
|---|---|---|
| Overall diameter | 29.65″ | 30.18″ |
| Section width | 9.65″ (245 mm) | 9.25″ (235 mm) |
| Sidewall height | 4.82″ (50%) | 5.09″ (55%) |
| Rim diameter | 20″ | 20″ |
| Circumference | 93.13″ | 94.8″ |
| Revs per mile | 680 | 668 |
Interactive comparison
275/65R18 or "33" for inch aliases245/50R20
- Diameter
- 29.65″ / 753mm
- Section Width
- 9.65″
- Sidewall
- 4.82″ / 122.5mm
- Circumference
- 93.13″
- Revs/Mile
- 680
235/55R20
- Diameter
- 30.18″ / 766.5mm
- Section Width
- 9.25″
- Sidewall
- 5.09″ / 129.25mm
- Circumference
- 94.8″
- Revs/Mile
- 668
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 61.08 mph (98.29 km/h). Your speedometer reads 1.79% low versus actual speed.