255/45R20 vs 245/50R20
245/50R20 is taller than 255/45R20 by 2.10% — a diameter difference of 0.61″.
What changes between 255/45R20 and 245/50R20
Switching from 255/45R20 to 245/50R20 changes overall diameter by +2.10%, a taller tire by 0.61 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 +0.30″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -15, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 66.4 mph. Both sizes share the same 20″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 255/45R20 | 245/50R20 |
|---|---|---|
| Overall diameter | 29.04″ | 29.65″ |
| Section width | 10.04″ (255 mm) | 9.65″ (245 mm) |
| Sidewall height | 4.52″ (45%) | 4.82″ (50%) |
| Rim diameter | 20″ | 20″ |
| Circumference | 91.22″ | 93.13″ |
| Revs per mile | 695 | 680 |
Interactive comparison
275/65R18 or "33" for inch aliases255/45R20
- Diameter
- 29.04″ / 737.5mm
- Section Width
- 10.04″
- Sidewall
- 4.52″ / 114.75mm
- Circumference
- 91.22″
- Revs/Mile
- 695
245/50R20
- Diameter
- 29.65″ / 753mm
- Section Width
- 9.65″
- Sidewall
- 4.82″ / 122.5mm
- Circumference
- 93.13″
- Revs/Mile
- 680
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 61.26 mph (98.59 km/h). Your speedometer reads 2.10% low versus actual speed.