To celebrate National Bike Month, explore history and evolution of the bicycle wheel in this excerpt from The Bike Deconstructed: A Grand Tour of the Modern Bicycle by Richard Hallet.
The bicycle wheel is a highly sophisticated and yet a durable and easily maintained structure. Able to support over 100 times its own weight, stiff and resilient, and suitable for manufacture using low-cost or high-tech materials as required, it is surely the most intricate piece of engineering in a road bike.
Early cart wheel
Wheels fitted to the earliest bicycle, the Michaux velocipede or “boneshaker,” were, in essence, cart wheels. The method of construction was proven to work for carts and carriages and there was nothing better available. It presented the early bike makers with two basic drawbacks: it created a wheel that was, like everything else about the velocipede, both heavy and rigid because the spokes, made of wood, worked in compression; the spoke at the bottom of the wheel where it touched the ground supported the hub and bike (or cart) weighing down upon it.
Introducing wire spokes
Progress was rapid. The tensioned wire spoke appeared in 1869 in a radical machine called the Phantom. Then in 1871 came the Ariel bicycle introduced by the English bike engineer James Starley — otherwise known as the father of the bicycle industry.
The Phantom
The Phantom was presumably given its name because, weighing some 53lb (24kg) it was insubstantial compared to its predecessors. Its frame was made of iron rods and was articulated in the middle, but as if that weren’t enough, its wheels featured wire spokes held in tension between the rim and the hub flanges so that the rim was suspended from the spokes arrayed around the top half of the wheel.
Pulling inward on the rim, the spokes could be much thinner and, taken together, lighter than a few wooden spokes in compression. The Phantom’s spokes were arranged in pairs, each comprising a single length of wire passed through a loop in the rim and bent into a “V” with the ends secured at the hub. Tension was applied to all the spokes at once by forcing the hub flanges apart to increase the distance from rim to flange. Radiating out from the hub to the rim in conventional cart wheel style, the spokes in the bike’s driving wheel would have allowed the front hub to twist within the rim when force was applied to the pedals.
The Ariel
The Ariel bicycle improved on the Phantom’s method of tensioning the spokes by fitting the front wheel with a bar running across the hub through the middle of the wheel. From the trailing ends of the bar ran adjustable tie-rods, which were attached to the rim. They served to pull it around the hub and thus apply tension to the spokes.
Pulled at a tangent by the hub, the tie rods also ensured there would be no “wind-up” of the hub under pedaling. Starley followed up this idea by patenting the tangent-spoked wheel in the annus mirabilis of 1874, when W. H. J. Grout of Stoke Newington, UK, also patented a method of adjusting spoke tension by means of threaded nipples located in the rim. Arguments over the merits of tangent versus radial spokes continued for a decade and radial spoke lacing continued to be used in some ordinary or high-wheel bicycles until their demise.
Attaching spokes to wheel rims
By 1895, when the ordinary bicycle had all but disappeared, the radial spoke pattern had been abandoned in favor of J-bend tangent spokes located in flanged hubs with nipples at the rim. The bike wheel had arrived at something approaching its classic form, although rim technology still offered plenty of scope for experiment and improvement.
Cycle tires were, as now, essentially of two types: one-piece tubular tires stuck to the rim were favored for racing while wired-on tires that allowed ready access to the inner tube were the choice for leisure use. Wired-on tire rims were made of pressed and rolled steel sheet or, in the case of some luxury machines, aluminum strip. By the early 1970s, aluminum wired-on rims were a common fitment on sports roadsters but employed a weak, flexible single-wall profile.
Wooden rims
For a several decades, the finest racing bikes rolled on wooden rims wearing tubular tires. Wood proved a material well-suited to the application; spoke tension pulls the rim inward, putting it in compression. Wood’s low density means a wooden rim can have the large cross-sectional area needed in a compression member, allowing the wheel to be built with greater spoke tension and therefore fewer spokes than is possible in a wheel with the necessarily thin folded strip of a reasonably light steel rim. It is also easy to shape to the cross section required for a glued-on tubular tire.
Aluminum rims
For the 1934 Tour de France, the ever-innovative French firm Mavic supplied leading professional road racer Antonin Magne with double-wall or box-section hollow aluminum rims of a revolutionary new design featuring pressed-steel reinforcing eyelets let into the rim. Each eyelet comprised a top-hat shape stamped out of sheet steel with a nipple-sized hole in the crown. The eyelet sat in a hole in the rim outer wall the same diameter as its sleeve section with the brim resting against the outer wall and the face of the crown resting against the inside in the inner wall. Thus the brim and crown shared the pull of the spoke nipple between the rim’s inner and outer walls. Without the eyelet, the inner, hub-side wall of the rim’s box section needed to be thick and therefore heavy to resist the pull of the spoke.
As such novelties were forbidden by the race rules, the rims were painted to look like wood to avoid detection. Although comparable in weight with wooden racing rims, they proved much stiffer and gave Magne a huge competitive advantage that he used to win the Tour in convincing style, beating his nearest challenger by over 27 minutes and recording an average speed of more than 19.3mph (31kph) for the first time in the event’s history.
Amazingly, this major advance over previous attempts to make light but durable aluminum rims was developed simultaneously by Mavic and an Italian designer Mario Longhi, who filed his patent two hours before Mavic, but thereafter allowed the French firm to manufacture eyelets rims until the patent expired in 1947. In order to avoid infringing on the Mavic-Longhi patent, rivals tried alternative methods of stiffening the hollow rim, such as sandwiching a wooden strip inside it.
The double-eyeletted rim proved the best design and Mavic improved it still further with a patent registered in 1966. The eyelet was fixed firmly to the inner rim wall by crimping a small tubular protrusion pushed through the spoke hole. This is the method of anchoring the spoke nipple still widely used today for both tubular and clincher rims with a hollow-box cross section. Some lightweight aluminum rims omit the eyelet and rely on a roughly delta-shaped profile, with the nipple at its tip, to resist spoke tension.
The hollow box section of the tubular or “sprint” rim makes for a very light structure but was not found on rims suitable for wired-on tires until the arrival of the Mavic Module E rim and Michelin’s matching Elan tire. Together, they immediately improved the performance of the wired-on or clincher tire to the point where it was comparable to that of a heavy-duty training tubular and, as clincher performance steadily improved, to that of even the fastest of road-racing tubs.
“Factory-built” rims
Recent developments in wheel manufacturing have centered on perfecting the “factory-built” wheelset, which has largely replaced the handbuilt wheel for all but touring and audax riding, and on finding improvements in wheel aerodynamics. Rims designed using computational fluid dynamics (CFD) and manufactured in carbon fiber demonstrate a marked reduction in air drag but can weigh as little as a box-section aluminum sprint rim. Their cost is high and the challenge for the industry is to make such speedy wheels available to all road cyclists.
The Bike Deconstructed: A Grand Tour of the Modern Bicycle is available from:
Author Richard Hallett, former editor of RoadCyclingUK.com, is well known in the bicycle world for his knowledge of the intricacies of cycling technology.
