Wheel Fitment, Tyre Stretch, Rolling Radius and Speedometer Error Calculator
Insert your existing wheel and tyre specs, and the desired size, and the outcome is shown on the diagram. Bear in mind most tyre manufacturers vary slighty from the specs, and that it could be dangerous to run tyres on wheels they aren't designed to fit. The strut shown in the diagram is for show only - Don't worry if the wheel looks like it fouls!