245/50R20 vs 285/45R20
285/45R20 is taller than 245/50R20 by 1.53% — a diameter difference of 0.45″.
What changes between 245/50R20 and 285/45R20
Switching from 245/50R20 to 285/45R20 changes overall diameter by +1.53%, a taller tire by 0.45 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 +0.23″: 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 | 245/50R20 | 285/45R20 |
|---|---|---|
| Overall diameter | 29.65″ | 30.1″ |
| Section width | 9.65″ (245 mm) | 11.22″ (285 mm) |
| Sidewall height | 4.82″ (50%) | 5.05″ (45%) |
| Rim diameter | 20″ | 20″ |
| Circumference | 93.13″ | 94.56″ |
| Revs per mile | 680 | 670 |
Interactive comparison
275/65R18 or "33" for inch aliases245/50R20
- Diameter
- 29.65″ / 753mm
- Section Width
- 9.65″
- Sidewall
- 4.82″ / 122.5mm
- Circumference
- 93.13″
- Revs/Mile
- 680
285/45R20
- Diameter
- 30.1″ / 764.5mm
- Section Width
- 11.22″
- Sidewall
- 5.05″ / 128.25mm
- Circumference
- 94.56″
- Revs/Mile
- 670
Speedometer & Diameter Impact
Wider tire — verify wheel widthAt an indicated 60 mph, your actual speed is 60.92 mph (98.04 km/h). Your speedometer reads 1.53% low versus actual speed.