The 255/45R18 is a common tire size for SUVs and crossovers such as Toyota RAV4, Honda CR-V, and Ford Explorer.
With a 114.8 mm sidewall (45% aspect ratio), this tire offers a balanced blend of ride comfort and handling precision — versatile for both city driving and spirited cornering.
Compared to the baseline 235/45R18, this tire's overall diameter differs by +2.7% — a speedometer calibrated for 235/45R18 would read 97.4 km/h at an actual 100 km/h.
OE on the Audi A8 (D4), Mercedes-Benz E-Class (W212) base and Porsche Panamera (970) base. Load index 99W or 103Y reinforced. Used both as a square fitment on luxury sedans and as a front pair in staggered setups with 275/40R19 rear.
Mainstream sedan sizes balance compound longevity against light all-season handling. When replacing, match the OE speed rating (H or V on most trims) — installing a lower rating voids many manufacturer load-test certifications and is illegal on autobahn-rated vehicles. Wheel-well clearance is rarely a concern at this rim diameter; speedometer drift across factory alternatives stays well inside the ±3% legal window.
| Tire Code | 255/45R18 |
| Section Width | 255 mm |
| Aspect Ratio | 45% |
| Rim Diameter | 18" |
| Sidewall Height | 114.8 mm |
| Overall Diameter | 686.7 mm / 27.04" |
| Circumference | 2157.3 mm / 84.93" |
| Revolutions per km | 463.5 |
| Revolutions per mile | 746.0 |
| Tire Code | OD (mm) | Δ mm | Δ % | Speedo at 100 km/h |
|---|---|---|---|---|
| 255/40R18 | 661.2 | -25.5 | -3.7% | 103.9 |
| 235/45R18 | 668.7 | -18.0 | -2.6% | 102.7 |
| 245/45R18 | 677.7 | -9.0 | -1.3% | 101.3 |
| 255/45R18 (current) | 686.7 | — | — | 100.0 |
| 255/45R19 | 712.1 | +25.4 | +3.7% | 96.4 |
| 255/45R20 | 737.5 | +50.8 | +7.4% | 93.1 |
| 255/55R18 | 737.7 | +51.0 | +7.4% | 93.1 |