The 215/40R18 is a common tire size for performance and sports cars such as BMW 3 Series, Volkswagen GTI, and Audi A4.
With a 86.0 mm sidewall (40% aspect ratio), this low-profile tire delivers sharp steering response and precise cornering grip, though the ride feels firmer over rough surfaces.
Compared to the baseline 235/45R18, this tire's overall diameter differs by -5.9% — a speedometer calibrated for 235/45R18 would read 106.3 km/h at an actual 100 km/h.
When replacing, verify that your wheel well can accommodate the 629.2 mm overall diameter. Keep speedometer deviation within ±3% for safety and legal compliance.
| Tire Code | 215/40R18 |
| Section Width | 215 mm |
| Aspect Ratio | 40% |
| Rim Diameter | 18" |
| Sidewall Height | 86.0 mm |
| Overall Diameter | 629.2 mm / 24.77" |
| Circumference | 1976.7 mm / 77.82" |
| Revolutions per km | 505.9 |
| Revolutions per mile | 814.2 |
| Tire Code | OD (mm) | Δ mm | Δ % | Speedo at 100 km/h |
|---|---|---|---|---|
| 215/40R18 (current) | 629.2 | — | — | 100.0 |
| 225/40R18 | 637.2 | +8.0 | +1.3% | 98.7 |
| 235/40R18 | 645.2 | +16.0 | +2.5% | 97.5 |
| 215/45R18 | 650.7 | +21.5 | +3.4% | 96.7 |