Amongst the more performance-oriented parts of the cycling community, there is something of an aversion to small wheels. Large wheels have certain benefits, they deal with uneven surfaces better than small wheels and the wheel does fewer revolutions for a given distance, leading to longer tyre life.
There is a common misconception that larger wheels are faster. At very high speeds, there are benefits to larger wheels due to the gyroscopic effect, but these only come into effect at speeds seldom sustained for long by even professional cyclists. At low speeds, the reduced weight and air resistance of a smaller wheel makes them faster than their larger counterparts, making them ideal for transportation use in start-stop traffic.
An original Moulton bicycle from the 1960s, spotted in Chorlton.
The 200 m flying start world speed record for a bike using the conventional riding position was set on a modern Moulton in 1985.
Another advantage of a smaller wheel is strength. Shorter spokes make for a stronger wheel, just look at the amount of punishment the 20 inch wheels used by BMXers are put through. The strength of smaller wheels is also put to clever use in the Madsen bicycle and the Bakfiets (images taken from respective sites):
Madsen bucket bike
Smaller wheels make hub-based brakes more effective. Drums, rollers and discs all work better on smaller sized wheels due to their central location. I use a drum brake on my Raleigh Twenty and it is more powerful than the same unit on my DL-1.
As has been discussed over at Lovely Bicycle! smaller wheels increase the range of rider sizes which can be accommodated. Sadly, the desire on the manufacturers’ part to only use one wheel size for a given model means that proportionally smaller wheels are seldom used for smaller sized frames (such as 650Bs on a smaller touring bike rather than 700Cs). Added to this is the common misconception that smaller wheels are slower, meaning that small wheeled bikes for touring are still a niche market (The Moulton being the only small-wheeled dedicated touring bike which springs to mind).
The Raleigh Twenty was Raleigh’s more-affordable answer to the original Moulton. Raleigh eventually owned Moulton for a time.
Small wheels are also more manoeuvrable, which is a desirable trait when riding in traffic, as many Bromptonauts will agree. Finally, small wheels are easier to store. This is not just useful for folding bikes like the aforementioned Brompton, but also for rigid bikes such as the Moulton and the Twenty. The Twenty doesn’t get the same special treatment on the train as a folder, but it is much easier to take in and out of a train, or to squeeze into a gap somewhere during busy periods. It is also easy to take into a house rather than lock up outside, and the small wheels make the whole package easy to carry up a flight of stairs.
Type M Brompton. Brompton, like Pashley and Moulton are one of the few companies to still make their bikes in the UK
Small and large wheels each have their own advantages, when choosing a bike, don’t count small wheels out too quickly.