275/55R20 vs 245/65R20
245/65R20 is taller than 275/55R20 by 1.97% — a diameter difference of 0.63″.
What changes between 275/55R20 and 245/65R20
Switching from 275/55R20 to 245/65R20 changes overall diameter by +1.97%, a taller tire by 0.63 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 -1.18″ (275mm → 245mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.32″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -12, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 66.3 mph. Both sizes share the same 20″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 275/55R20 | 245/65R20 |
|---|---|---|
| Overall diameter | 31.91″ | 32.54″ |
| Section width | 10.83″ (275 mm) | 9.65″ (245 mm) |
| Sidewall height | 5.95″ (55%) | 6.27″ (65%) |
| Rim diameter | 20″ | 20″ |
| Circumference | 100.25″ | 102.23″ |
| Revs per mile | 632 | 620 |
Interactive comparison
275/65R18 or "33" for inch aliases275/55R20
- Diameter
- 31.91″ / 810.5mm
- Section Width
- 10.83″
- Sidewall
- 5.95″ / 151.25mm
- Circumference
- 100.25″
- Revs/Mile
- 632
245/65R20
- Diameter
- 32.54″ / 826.5mm
- Section Width
- 9.65″
- Sidewall
- 6.27″ / 159.25mm
- Circumference
- 102.23″
- Revs/Mile
- 620
Speedometer & Diameter Impact
Narrower tire — verify wheel widthAt an indicated 60 mph, your actual speed is 61.18 mph (98.47 km/h). Your speedometer reads 1.97% low versus actual speed.