245/45R18 vs 215/55R18
215/55R18 is taller than 245/45R18 by 2.36% — a diameter difference of 0.63″.
What changes between 245/45R18 and 215/55R18
Switching from 245/45R18 to 215/55R18 changes overall diameter by +2.36%, 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 -1.19″ (245mm → 215mm), 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 -18, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 66.5 mph. Both sizes share the same 18″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 245/45R18 | 215/55R18 |
|---|---|---|
| Overall diameter | 26.68″ | 27.31″ |
| Section width | 9.65″ (245 mm) | 8.46″ (215 mm) |
| Sidewall height | 4.34″ (45%) | 4.66″ (55%) |
| Rim diameter | 18″ | 18″ |
| Circumference | 83.82″ | 85.8″ |
| Revs per mile | 756 | 738 |
Interactive comparison
275/65R18 or "33" for inch aliases245/45R18
- Diameter
- 26.68″ / 677.7mm
- Section Width
- 9.65″
- Sidewall
- 4.34″ / 110.25mm
- Circumference
- 83.82″
- Revs/Mile
- 756
215/55R18
- Diameter
- 27.31″ / 693.7mm
- Section Width
- 8.46″
- Sidewall
- 4.66″ / 118.25mm
- Circumference
- 85.8″
- Revs/Mile
- 738
Speedometer & Diameter Impact
Narrower tire — verify wheel widthAt an indicated 60 mph, your actual speed is 61.42 mph (98.84 km/h). Your speedometer reads 2.36% low versus actual speed.