245/60R20 vs 285/55R20
285/55R20 is taller than 245/60R20 by 2.43% — a diameter difference of 0.77″.
What changes between 245/60R20 and 285/55R20
Switching from 245/60R20 to 285/55R20 changes overall diameter by +2.43%, a taller tire by 0.77 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 +1.57″ (245mm → 285mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.38″: 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 66.6 mph. Both sizes share the same 20″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 245/60R20 | 285/55R20 |
|---|---|---|
| Overall diameter | 31.57″ | 32.34″ |
| Section width | 9.65″ (245 mm) | 11.22″ (285 mm) |
| Sidewall height | 5.79″ (60%) | 6.17″ (55%) |
| Rim diameter | 20″ | 20″ |
| Circumference | 99.2″ | 101.61″ |
| Revs per mile | 639 | 624 |
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
285/55R20
- Diameter
- 32.34″ / 821.5mm
- Section Width
- 11.22″
- Sidewall
- 6.17″ / 156.75mm
- Circumference
- 101.61″
- Revs/Mile
- 624
Speedometer & Diameter Impact
Wider tire — verify wheel widthAt an indicated 60 mph, your actual speed is 61.46 mph (98.91 km/h). Your speedometer reads 2.43% low versus actual speed.