A tool that determines the overall size of a tire when fully inflated and not under load. This calculation is based on the tire’s sidewall markings, specifically the tire width, aspect ratio, and rim diameter. As an example, a tire marked 225/50R17 indicates a width of 225 millimeters, an aspect ratio of 50% (meaning the sidewall height is 50% of the width), and a rim diameter of 17 inches. These figures are then used in a formula to derive the overall measurement from bead to bead.
Understanding the fully inflated size of a tire offers several advantages. It aids in selecting appropriate replacements that maintain correct speedometer readings, ensure proper vehicle clearance, and preserve handling characteristics. Historically, determining this measurement required manual calculations, which were prone to error. Modern tools automate this process, providing accurate results quickly and efficiently, mitigating potential issues related to incorrect tire sizing.
