How do Small Wheels Ride? (Part 2)

So, last time we looked at some of the issues that lead to small wheels producing a harsher / less comfortable ride relative to traditional wheel sizes. At the end of the article I promised to look at technological solutions to this problem, and true to word, here we are. The best place to start oddly enough is England in the middle of the 20th century where Sir Alex Moulton, fresh off designing the suspension system for the mini (a car with very tiny wheels) decided to improve upon the diamond frame bicycle. Noting that the bicycle had changed little since the safety frame burst on the scene in the waning years of the 19th century, Moulton concluded that, like all other forms of transportation, the wheel size on bicycles should shrink. However, keenly aware of the issues we looked at last time, he decided that a narrow diameter, high pressure tire, in combination with a suspension system could produce rolling comfort and efficiency in line with standard wheel sizes, while having all the advantage that come with small wheels. His first effort was a huge commercial success and an iconic piece of 1960's Britain: The Moulton F-frame. The front suspension is somewhat obvious, and the second picture is a close-up on the rear suspension, which is basically a block of rubber that the rear triangle / fork can compress. (It is in fact more like a fork if you look closely at it.)


This basic concept is employed by a number of other folding bike manufacturers, perhaps most notably by Brompton. The Brompton design, developed by Andrew Ritchie in 1975 employs the rear suspension block in a rather ingenious fashion -- the entire rear triangle is free to swing under the bike when folding, or compress the rubber block while riding.


The Brompton does not offer any front suspension out side of stem flex, which from my personal experience is minimal. One company though decided that through some clever design and user specific tuning of tube thicknesses that comfort could be achieved through stem and seat tube flex. Enter, Bike Friday:

This particular model, the Air Friday employs a titanium suspension bean in lieu of a more traditional seat tube (as is used on most Bike Fridays) along with the custom "Goose Neck" stem that also provides some forgiveness while riding. Just in case this whole frame flex option seems insufficient to you, there is also the Pantour suspension hub. These special hubs offer up to 1 inch of self contained travel.

They are a popular aftermarket upgrade for Brompton Bicycles and are perhaps most easily found on the Dahon Speed Pro, which ships with a suspension front hub.

Dahon also takes a more simplistic approach to suspension in a number of its folding bikes, notably the Curve series -- larger volume tires. Though some of the rolling efficiency of high pressure, narrow tires is lost (as it would be with any balloon tired cruiser), the added comfort is appreciated. Furthermore, since speed loss is minimal, and these particular bikes are not intended for racing, balloon tires can be a cheap and effective way to overcome some of the drawbacks of small wheels.

In contrast to this approach, Alex Moulton further refined his popular design started in the early 1980's and most recently with the AM New Series. Aside from the obvious lattice work "Space Frame", these bicycles feature a more advanced fluid dampened rear suspension and a parallelogram suspension fork. This design was so impressive as to earn a spot in New York's Museum of Modern Art.

One last approach come from Riese & Muller's Birdy line and is in many ways a modification of the Moulton design. It is notable in that the front parallelogram suspension separates and is actually integral to folding the bicycle.

I hope you enjoyed this tour of the wide variety of suspension mechanisms employed in the small wheeled world. The diversity of design found in small wheeled bicycles and folding bicycles in particular is one of the reasons for my continued interest in the subject, so I hope you found this cursory look enjoyable. Next time, I will look at some of less obvious advantages of small wheeled bicycles and talk a bit about my personal experiences riding them; in the mean time though, get up, and go ride.