Question: what size are my bike tyres?
Answer: Tyre Sizes The size of bike tyres is normally shown by two numbers, which give the size of the wheel it's designed for as well as the width of the tyre. You might see this written as 700x23c (a 23mm wide tyre for a 700c wheel) or 26x2. 1" (a 2.1 inch wide tyre for a 26 inch wheel).