245/60R20 vs 255/60R20
255/60R20 is taller than 245/60R20 by 1.50% — a diameter difference of 0.48″.
What changes between 245/60R20 and 255/60R20
Switching from 245/60R20 to 255/60R20 changes overall diameter by +1.50%, a taller tire by 0.48 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″ (245mm → 255mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.23″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -10, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 66.0 mph. Both sizes share the same 20″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 245/60R20 | 255/60R20 |
|---|---|---|
| Overall diameter | 31.57″ | 32.05″ |
| Section width | 9.65″ (245 mm) | 10.04″ (255 mm) |
| Sidewall height | 5.79″ (60%) | 6.02″ (60%) |
| Rim diameter | 20″ | 20″ |
| Circumference | 99.2″ | 100.68″ |
| Revs per mile | 639 | 629 |
Interactive comparison
275/65R18 or "33" for inch aliases245/60R20
- Diameter
- 31.57″ / 802mm
- Section Width
- 9.65″
- Sidewall
- 5.79″ / 147mm
- Circumference
- 99.2″
- Revs/Mile
- 639
255/60R20
- Diameter
- 32.05″ / 814mm
- Section Width
- 10.04″
- Sidewall
- 6.02″ / 153mm
- Circumference
- 100.68″
- Revs/Mile
- 629
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 60.9 mph (98.01 km/h). Your speedometer reads 1.50% low versus actual speed.