But if you've ever tried to build or restore a bike then the exact size of wheels can become very important to you, especially if you've bought a bike with almost no provenience, and crucially if you've bought a vintage bike. So because I'm a helpful elf type I'm going to give you a very quick rundown of bike wheel sizes:
Bike wheel size chart
(wheel size followed by typical usage)
- 27" x 111/4" - Old touring bikes
- 700c - If you have a road bike (racer) made in the last twenty years then this is probably the wheel size that you have
- 16" x 1 3/8" - These days mostly used on Brompton folding bikes
There's a LOT more information (including ISO numbers) over on the ever-crucial Sheldon Brown website...