265/45R20 vs 255/50R20
255/50R20 is taller than 265/45R20 by 2.21% — a diameter difference of 0.65″.
What changes between 265/45R20 and 255/50R20
Switching from 265/45R20 to 255/50R20 changes overall diameter by +2.21%, a taller tire by 0.65 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″ (265mm → 255mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.33″: 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 | 265/45R20 | 255/50R20 |
|---|---|---|
| Overall diameter | 29.39″ | 30.04″ |
| Section width | 10.43″ (265 mm) | 10.04″ (255 mm) |
| Sidewall height | 4.69″ (45%) | 5.02″ (50%) |
| Rim diameter | 20″ | 20″ |
| Circumference | 92.33″ | 94.37″ |
| Revs per mile | 686 | 671 |
Interactive comparison
275/65R18 or "33" for inch aliases265/45R20
- Diameter
- 29.39″ / 746.5mm
- Section Width
- 10.43″
- Sidewall
- 4.69″ / 119.25mm
- Circumference
- 92.33″
- Revs/Mile
- 686
255/50R20
- Diameter
- 30.04″ / 763mm
- Section Width
- 10.04″
- Sidewall
- 5.02″ / 127.5mm
- Circumference
- 94.37″
- Revs/Mile
- 671
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 61.33 mph (98.69 km/h). Your speedometer reads 2.21% low versus actual speed.