215/55R18 vs 275/45R18
275/45R18 is taller than 215/55R18 by 1.59% — a diameter difference of 0.43″.
What changes between 215/55R18 and 275/45R18
Switching from 215/55R18 to 275/45R18 changes overall diameter by +1.59%, a taller tire by 0.43 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 +2.37″ (215mm → 275mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.21″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -11, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 66.0 mph. Both sizes share the same 18″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 215/55R18 | 275/45R18 |
|---|---|---|
| Overall diameter | 27.31″ | 27.74″ |
| Section width | 8.46″ (215 mm) | 10.83″ (275 mm) |
| Sidewall height | 4.66″ (55%) | 4.87″ (45%) |
| Rim diameter | 18″ | 18″ |
| Circumference | 85.8″ | 87.16″ |
| Revs per mile | 738 | 727 |
Interactive comparison
275/65R18 or "33" for inch aliases215/55R18
- Diameter
- 27.31″ / 693.7mm
- Section Width
- 8.46″
- Sidewall
- 4.66″ / 118.25mm
- Circumference
- 85.8″
- Revs/Mile
- 738
275/45R18
- Diameter
- 27.74″ / 704.7mm
- Section Width
- 10.83″
- Sidewall
- 4.87″ / 123.75mm
- Circumference
- 87.16″
- Revs/Mile
- 727
Speedometer & Diameter Impact
Wider tire — verify wheel widthAt an indicated 60 mph, your actual speed is 60.95 mph (98.09 km/h). Your speedometer reads 1.59% low versus actual speed.