245/45-R17 tires are 0.65 inches (16.5 mm) larger in diameter than 255/40-R17 tires and the speedometer difference is 2.5%.
Published by Dustin Babich on 12 June 2023. The main difference between 245/45zr20 and 245/45r20 is the tire type. A ‘z’ rating means the tire has a speed rating of over 149 mph, while ‘r’ indicates a standard performance tire with a maximum speed of 106 mph. Both refer to the same size of tire – 245mm width, 45mm aspect ratio, and a245/40-R19 tires are 0.31 inches (8 mm) larger in diameter than 235/40-R19 tires and the speedometer difference is 1.2%.
245/40-R17 tires are 0.26 inches (6.5 mm) smaller in diameter than 225/45-R17 tires and the speedometer difference is 1.0%.
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