The Cateye Tire Size Calculator is a great tool. If you are looking for Wheel Size Diameter in mm and do not want to be bothered with entering data into the Cateye tool, I have used these successfully:
20 x 1.50 = 1490
20 x 1.75 = 1502
20 x 1.95 = 1575
These are approximations. Tires from different manufacturers will vary slightly and you may have to adjust accordingly.
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Don
Last edited by GeezyRider; 04-03-21 at 03:52 PM.