255/55R20 vs 245/60R20
245/60R20 is taller than 255/55R20 by 1.71% — a diameter difference of 0.53″.
What changes between 255/55R20 and 245/60R20
Switching from 255/55R20 to 245/60R20 changes overall diameter by +1.71%, 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 -0.39″ (255mm → 245mm), 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 -11, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 66.1 mph. Both sizes share the same 20″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 255/55R20 | 245/60R20 |
|---|---|---|
| Overall diameter | 31.04″ | 31.57″ |
| Section width | 10.04″ (255 mm) | 9.65″ (245 mm) |
| Sidewall height | 5.52″ (55%) | 5.79″ (60%) |
| Rim diameter | 20″ | 20″ |
| Circumference | 97.53″ | 99.2″ |
| Revs per mile | 650 | 639 |
Interactive comparison
275/65R18 or "33" for inch aliases255/55R20
- Diameter
- 31.04″ / 788.5mm
- Section Width
- 10.04″
- Sidewall
- 5.52″ / 140.25mm
- Circumference
- 97.53″
- Revs/Mile
- 650
245/60R20
- Diameter
- 31.57″ / 802mm
- Section Width
- 9.65″
- Sidewall
- 5.79″ / 147mm
- Circumference
- 99.2″
- Revs/Mile
- 639
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 61.03 mph (98.21 km/h). Your speedometer reads 1.71% low versus actual speed.