QUESTION: I’m confused about all the different terminology for bicycle wheel sizes. Just tell me straight, which size is a road bike wheel? – Justin T
ANSWER: Well, it’s unfortunately a little bit more complicated than that. I can tell you which size is the most common size for road bike wheels, but that’s not the only size available, period.
If you’re an average sized man or woman shopping for a road bike from a major manufacturer at a local bike shop, then chances are very high that your road bike wheel size is going to be 700c. That’s generally going to be the case whether it’s a pure road bike, a hybrid bike, a cyclocross bike or a triathlon / time trial bike.
Although the vast majority of the time you’re going to see a 700c wheel on these bikes, there are a few exceptions.
1. Gravel and adventure style bikes often have the option for a smaller 650b wheel, because this allows them to use a wider tire inside the frame. Many of them allow you to switch between 700c and 650b, so you can run either size.
2. If it is a women’s road bike designed for shorter women, it might have 650c wheels, which are different than 650b wheels, although similarly named. These are smaller wheels that work better with an extremely small frame.
3. If it’s a very old road bike, and especially a touring road bike, it might have 27 inch wheels, also known as ISO 630.
Mountain bikes are an entirely different story, and not covered here because it’s too big of a topic to include.