225/45R18 vs 215/50R18
215/50R18 is taller than 225/45R18 by 1.89% — a diameter difference of 0.49″.
What changes between 225/45R18 and 215/50R18
Switching from 225/45R18 to 215/50R18 changes overall diameter by +1.89%, a taller tire by 0.49 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 -0.40″ (225mm → 215mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.24″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -15, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 66.2 mph. Both sizes share the same 18″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 225/45R18 | 215/50R18 |
|---|---|---|
| Overall diameter | 25.97″ | 26.46″ |
| Section width | 8.86″ (225 mm) | 8.46″ (215 mm) |
| Sidewall height | 3.99″ (45%) | 4.23″ (50%) |
| Rim diameter | 18″ | 18″ |
| Circumference | 81.59″ | 83.14″ |
| Revs per mile | 777 | 762 |
Interactive comparison
275/65R18 or "33" for inch aliases225/45R18
- Diameter
- 25.97″ / 659.7mm
- Section Width
- 8.86″
- Sidewall
- 3.99″ / 101.25mm
- Circumference
- 81.59″
- Revs/Mile
- 777
215/50R18
- Diameter
- 26.46″ / 672.2mm
- Section Width
- 8.46″
- Sidewall
- 4.23″ / 107.5mm
- Circumference
- 83.14″
- Revs/Mile
- 762
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 61.14 mph (98.39 km/h). Your speedometer reads 1.89% low versus actual speed.