255/50R20 vs 245/55R20
245/55R20 is taller than 255/50R20 by 1.90% — a diameter difference of 0.57″.
What changes between 255/50R20 and 245/55R20
Switching from 255/50R20 to 245/55R20 changes overall diameter by +1.90%, 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 -0.39″ (255mm → 245mm), 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 -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 | 255/50R20 | 245/55R20 |
|---|---|---|
| Overall diameter | 30.04″ | 30.61″ |
| Section width | 10.04″ (255 mm) | 9.65″ (245 mm) |
| Sidewall height | 5.02″ (50%) | 5.31″ (55%) |
| Rim diameter | 20″ | 20″ |
| Circumference | 94.37″ | 96.16″ |
| Revs per mile | 671 | 659 |
Interactive comparison
275/65R18 or "33" for inch aliases255/50R20
- Diameter
- 30.04″ / 763mm
- Section Width
- 10.04″
- Sidewall
- 5.02″ / 127.5mm
- Circumference
- 94.37″
- Revs/Mile
- 671
245/55R20
- Diameter
- 30.61″ / 777.5mm
- Section Width
- 9.65″
- Sidewall
- 5.31″ / 134.75mm
- Circumference
- 96.16″
- Revs/Mile
- 659
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 61.14 mph (98.4 km/h). Your speedometer reads 1.90% low versus actual speed.