I already had my tires but wanted a very accurate backspace before I ordered my 15x12 wheels. I bought this tool. Use of the tool does require one to already have the tires they plan to use.


https://www.speedwaymotors.com/Wheel-Fitment-Tool-Tire-Fit-Size-Measuring-Mockup-4-Lug,508754.html?utm_medium=CSEGoogle&utm_source=CSE&utm_campaign=CSEGOOGLE&gad_source=1&gclid=EAIaIQobChMIjPq5x8qAhQMVSgOtBh1wXgOBEAQYCyABEgL4ifD_BwE