Wheely? Does Size Matter?

Size MattersI know there’s a difference in wheel sizes between certain types of mountain bikes and city bikes, but what do the differences mean and why should I care?

First let’s go over wheel sizes.

Mountain bikes were originally designed with 26-inch diameter wheels. The thinking back in the 1980’s was that to climb hills a rider could transfer more power per square inch to the wheel surface by reducing the traditional bike rim size. In addition, the resulting shorter overall bike length was more adept at clearing short turning radiuses. The only downside to this design is that it is less efficient on flats. But, then it is called mountain biking.

Road bikes have standardized on a larger 700c wheel size for exactly the opposite reasons. A longer overall bike length provides stability at speed and the larger rim size in combination with gearing reduces the amount of effort from the rider to achieve higher speeds. The ‘c’ in this system does not stand for centimeters. It stands for size c in an obsolete French system in which ‘a’ meant skinny, ‘b’ meant not so skinny and ‘c’ meant wider. All Greek to most, I know.

A couple of new standard wheel sizes have emerged in the mountain bike market. The 29er and the 650b (there’s that French again). The 29er is just that – a bike with 29-inch rims. These wheels are great at rolling over obstacles in environments where turning radius is not such a huge obstacle. They also provide a higher bottom bracket which means you don’t hit things as regularly. The effort to ride is similar to the 700 cm wheel size, but in the cushy 2-inch knobby tire format. 29ers attempt to blend the efficiency of the larger wheel size with the general inefficiency of suspension. In some conditions, this works great – and many people would argue that in cross-country and all mountain situations, they are the bomb. However, downhillers might still prefer 26-inch rims for their fast-twitch directional change capabilities and because they allow for forks with more travel.

To confuse matters further, bike designers recently decided to split the difference – creating the 650b – a 27.5 inch wheel that rolls better than the 26 inch rim, but reduces the turning radius of the 29er. Got it?

Hmmm.

Why should you care? Well, you might want to match the purpose of your riding with the wheel size. If you are riding around town for shopping, a larger wheel size might be just the ticket. Many city bikes come with the 700c wheel size to optimize efficiency. Some cruiser bikes come with the 26 inch rim – mostly to accommodate cushier tires that give a slower, but super plush ride.

I toured and commuted for over ten years on a suspension-less mountain bike frame with 26-inch wheels. To boost efficiency, I used the skinniest, un-knobbiest tires I could find that would fit the rims. They were called ‘City Slickers’. To be honest, that was so far back, there really weren’t any choices except road bikes and mountain bikes. Now there are so many options. I have a city bike with 700c wheel size for everyday riding to work, shopping and entertainment. I also have a 29er hardtail for off road adventure touring. To buy it I sold my full suspension 26-inch wheel mountain bike. I used it for three months as my everyday bike to break it in before a trip and it was a plush commuter.

When it comes down to it, maybe size doesn’t really matter after all. Find the bike you like — whether it has big or small wheels. Ride it! Then you can make modifications like changing tires or gearing to suit your needs.

Wheel sizes have their advantages and disadvantages, but none of them really matter if you don’t first like your bike.

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