700C vs 650B Wheels: Which One is Faster?

by Jeff Whitfield on | 0 Comments

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Rene Herse Barlow Pas 700C x 38 TC Tire
Rene Herse Barlow Pas 700C x 38 TC Tire

Ever since getting my road bike, I’ve embraced the idea of using multiple wheelsets to get the benefits of different wheel and tire sizes. Currently, there is a debate within the cycling industry on not only tire width but also wheel size. Many riders are considering 650B wheels so they can add wider tires onto their bikes. However, I think many riders are hesitant and aren’t sure about them due to the fear of them not rolling as fast as a 700C wheel. But is that true? Fortunately, Rene Herse has some answers.

After getting my 700C x 38 Barlow Pass TC tires, I’ve followed Rene Herse on what they have to say about current trends in the bike industry. My impression is that they’re a company with a long history and know a thing or two about bike tires. They also make it super easy to chose a Rene Herse tire.

In his recent post entitled “Why 700C wheels DON’T roll faster”, Jan Heine of Rene Herse dispels a lot of the myths about larger wheels and the situations where smaller wheels can actually be faster. The basic conclusion is that wider, more supple tires are faster on tougher terrain than skinnier ones. Accomplishing this requires a smaller wheel in many cases.

Last month, I wrote a bit about Ted King’s 300+ mile romp across Vermont. Jan Heine mentions this ride in his post and how he rode on a 650B x 48 Switchback Hill TC tire for it. For most rides, like the Dirty Kanza, Ted has chosen mostly 700C wheels with anywhere from a 38mm to a 44mm tire. So, why a 650B wheelset this time? The reasoning is pretty simple. Since this wasn’t a race, he wasn’t really going for speed and more along the lines of comfort and better handling. For such a long ride, having extra air and suppleness in the tire allows for more energy absorption. This made for a more smoother ride which, for such a long ride, really helped in the long run.

But, like all things, there are limitations. As Jan mentions in his article, all things being equal, a 48mm tire on a 700C versus a 650B wheel will roll differently. While they might have the same contact patch, the amount of flex will be different. A 700C tire wouldn’t have to flex as much as a 650B tire with an equivalent width and thus would technically offer better rolling resistance.

On top of that, a 700C tire will have a significantly larger diameter than a 650B tire of the same width. That too has an impact on not just speed but the amount of power required to keep the wheel rolling. At that point, technically the larger diameter wheel and tire will roll faster than a smaller one. But it also takes more power to get up to speed and keep it rolling.

I’ve noticed this to some degree with my 700Cx38 and 650Bx47 wheelsets. The difference in diameter between them are pretty significant. Climbing with the 650B wheelset feels a bit easier than the same climb in the same gear on the 700C wheelset. But the 700C wheelset feels faster with smoother handling on downhills.

So why not just use a 700C tire then? Well, the problem comes down to tire clearance. While bike makers are constantly designing bikes with more tire clearance, not everyone can fit wider 700C tires on a bike. As such, dropping down to a 650B tire is necessary in order to fit wider tire sizes.

Actually, it’s a bit more complicated than that. It’s not that wider is better per se. It’s really more of a combination both a wider tire and bigger wheel. Even then, you have to consider your goals. If smoother handling is your goal then an emphasis on a larger wheel might be in order. However, if you need quicker, more agile handling, a smaller wheel would likely serve your needs better. After that, you can choose to go as wide as your bike can handle.

Now, does that mean you have to go with a wider tire? Not really. The thing to consider is the type of terrain you normally ride. If you ride predominately on the road and nothing else then your choice of width boils down to a matter of personal preference. If the road conditions are always mostly smooth then the benefits of a wider tire might not even be that noticeable. However, if you ride mixed terrain where road conditions are a mixed bag as well then a wider tire would likely be a better choice. In that case, consider going as wide as your bike allows.

As Jan says, in the end, it comes down to how you want your bike to feel. But remember that you don’t have to worry so much about losing speed with a 650B wheel. It’s the feel of it that changes. And when it comes to feel the suppleness of the tire makes all the difference.



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