275/70R18 vs 305/65R18
305/65R18 is taller than 275/70R18 by 1.37% — a diameter difference of 0.45″.
What changes between 275/70R18 and 305/65R18
Switching from 275/70R18 to 305/65R18 changes overall diameter by +1.37%, 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 +1.18″ (275mm → 305mm), 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 -8, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 65.9 mph. Both sizes share the same 18″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 275/70R18 | 305/65R18 |
|---|---|---|
| Overall diameter | 33.16″ | 33.61″ |
| Section width | 10.83″ (275 mm) | 12.01″ (305 mm) |
| Sidewall height | 7.58″ (70%) | 7.81″ (65%) |
| Rim diameter | 18″ | 18″ |
| Circumference | 104.17″ | 105.59″ |
| Revs per mile | 608 | 600 |
Interactive comparison
275/65R18 or "33" for inch aliases275/70R18
- Diameter
- 33.16″ / 842.2mm
- Section Width
- 10.83″
- Sidewall
- 7.58″ / 192.5mm
- Circumference
- 104.17″
- Revs/Mile
- 608
305/65R18
- Diameter
- 33.61″ / 853.7mm
- Section Width
- 12.01″
- Sidewall
- 7.81″ / 198.25mm
- Circumference
- 105.59″
- Revs/Mile
- 600
Speedometer & Diameter Impact
Wider tire — verify wheel widthAt an indicated 60 mph, your actual speed is 60.82 mph (97.88 km/h). Your speedometer reads 1.37% low versus actual speed.