The tire width is a millimetre measurement for the width of the tire. For example 245 mm when reading a tire size of 245/50R18 90/90 - 21: 54V: F: MT2.15: 1.85-2. 70/90-R17 tires are 1.29 inches (32.8 mm) larger in diameter than 80/90-R15 tires and the speedometer difference is 5.9% 100/70-R17 tires are 0.16 inches (4 mm) smaller in diameter than 80/90-R17 tires and the speedometer difference is 0.7%. Aug 20, 2016 · A set of 110/70R17 front and 140/70/R17 rear went for SGD155. The Pirelli Angel CiTy or Angel CT was designed by Pirelli specifically for the Asian “small bikes” market – targeting at bikes around the 150-300cc range – who wants to upgrade from the OEM tires. The thread pattern and tire design was inspired by and derived from the 110/70-R12 tires are 0.39 inches (10 mm) larger in diameter than 90/80-R12 tires and the speedometer difference is 2.2% 120/70-R19 tires are 0.31 inches (8 mm) smaller in diameter than 110/80-R19 tires and the speedometer difference is 1.2%. 80/90-R16 tires are 0 inches (0 mm) smaller in diameter than 90/80-R16 tires and the speedometer difference is 0.0%. Cool and dignified cruising with the superior EXEDRA MAX. Tires for American Cruiser Model. Optimum compound and structure/pattern design for cruisers are used. Excellent dry and wet grip performances, as well as long wear life, have been achieved. Recommended for: 130/90-R18 tires are 0.71 inches (18 mm) larger in diameter than 120/90-R18 tires and the speedometer difference is 2.6%. Apr 1, 2012 · Example: 90/90-21. 90 x .90 = 81. 81 x 2 = 162 (to calculate for the top & bottom portion of tire) 162 / 25.4 = 6.38 (25.4 will convert metric number to the standard inch) 6.38 + 21 = 27.38" overall height (21 being the rim height for this one) This will work for any metric tire size automobile or bike. hhCS.