Sidewall (mm) = width × aspect ratio ÷ 100. Diameter (mm) = rim (in) × 25.4 + 2 × sidewall. Circumference = π × diameter. Actual speed = indicated speed × (new diameter ÷ original diameter). Measurements are nominal and may differ from mounted tire specifications.

Diameter similarity alone does not establish safe fitment. Check wheel width, offset, clearance, load index, speed rating, manufacturer approval and vehicle requirements.