When it comes to cycling, bigger isn't always better. While smaller wheels on an adult bike might look odd, they come with a number of advantages, especially for smaller riders. But even tall cyclists can benefit from wheels with a diameter of 24 inches or less, depending on their preferred style of biking.
The wheel size on the bike used to set the world speed record on an upright bike was 18 inches. Small wheels usually require fewer spokes to achieve the same stability as the common 26 to 28 inch wheels, and fewer spokes generate less turbulence drag than larger wheels, leading to higher speeds. As pointed out by Alexi Grewal, 1984 Olympic road race gold medalist, a small wheel is more efficient than a large wheel in speeds up to 16 mph. In speeds between 16 and 33 mph, small and large wheels are equally efficient. Only in speeds faster than 33 mph is a large wheel preferable, Grewal says.
When you're riding in downtown traffic and need to stop frequently, you will appreciate fast acceleration. Because smaller wheels weigh less, they create a lower moment of inertia. As a result, they get up to speed quicker and climb better.
Easier to Maneuver
Small wheels create a more maneuverable bike. Because of their size, they are more responsive to steering and they present increased tire compliance with the road surface because they get higher pressure per square inch on the ground. The superior maneuverability is particularly helpful on wet surfaces and in tight turns. In addition, the overall compact size of small-wheeled bicycles makes the bike sturdier as a whole.
If you like to travel with your bike, a small-wheeled edition fits more easily in any car. Many small-wheelers double as folding bikes, some of which can even be carried in a common backpack. The smaller wheeled bike editions also take up less space in storage, and due to their overall lightness they can easily be carried upstairs if you prefer to keep your bike inside your apartment.
Preferable for Short Riders
Not only are small-wheeled bicycles easier to get on and off, but they present further advantages for short adult riders. As technical writer Lennard Zinn writes in his "Mountain Bike Performance Handbook," a smaller wheel allows the small rider to "have a handlebar-to-saddle height relationship proportional to that of a big rider, rather than being forced to have a handlebar higher than the saddle."
Specialized Uses for Small Wheels
For certain occasions, other than children's bicycles, small wheels are a common choice. Carrier bicycles feature a small front wheel to create extra space for cargo. Folding bikes are often equipped with small wheels for easier stowing. BMX bikes most commonly use 20 inch wheels for optimized maneuverability and quick acceleration. And time-trial bicycles have a smaller front wheel to allow the rider to bend down even lower for the most aerodynamic riding position.