Question: what are bike tube sizes?
Answer: Sizes such as 26, 24, 20, 27.5, 29 and 700c are common tire diameters. The second number (after the X) is the width of your tire. The range for widths is usually between 1 and 3 inches. For example, a 26 x 1.75 size means the tire diameter is 26 inches and the tire width is 1.75 inches.