275/65R20 vs 305/60R20
305/60R20 is taller than 275/65R20 by 0.98% — a diameter difference of 0.34″.
What changes between 275/65R20 and 305/60R20
Switching from 275/65R20 to 305/60R20 changes overall diameter by +0.98%, a taller tire by 0.34 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 → 305mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.16″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -6, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 65.6 mph. Both sizes share the same 20″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 275/65R20 | 305/60R20 |
|---|---|---|
| Overall diameter | 34.07″ | 34.41″ |
| Section width | 10.83″ (275 mm) | 12.01″ (305 mm) |
| Sidewall height | 7.04″ (65%) | 7.2″ (60%) |
| Rim diameter | 20″ | 20″ |
| Circumference | 107.05″ | 108.1″ |
| Revs per mile | 592 | 586 |
Interactive comparison
275/65R18 or "33" for inch aliases275/65R20
- Diameter
- 34.07″ / 865.5mm
- Section Width
- 10.83″
- Sidewall
- 7.04″ / 178.75mm
- Circumference
- 107.05″
- Revs/Mile
- 592
305/60R20
- Diameter
- 34.41″ / 874mm
- Section Width
- 12.01″
- Sidewall
- 7.2″ / 183mm
- Circumference
- 108.1″
- Revs/Mile
- 586
Speedometer & Diameter Impact
Wider tire — verify wheel widthAt an indicated 60 mph, your actual speed is 60.59 mph (97.51 km/h). Your speedometer reads 0.98% low versus actual speed.