Tool description: Enter your old bias-ply tire size (format: width-rim diameter, e.g., 5.60-15) to get the closest modern radial equivalent, including sidewall height, total diameter, and speedometer impact.
Old bias-ply tires use a format like 5.60-15: 5.60 = section width in inches, 15 = rim diameter in inches. Aspect ratio is typically assumed to be around 90-100% for bias-ply tires. Our converter uses a standard aspect ratio of 82% for vintage bias tires.
Modern radial tires improve handling, fuel economy, and tread life. However, you must maintain the same overall diameter (±3%) to keep your speedometer accurate and avoid clearance issues.
Last updated: May 10, 2026