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A man working on a bicycle wheel, circa 1890s.
Before bicycles worked well, they looked good. As a means of safe and reliable locomotion, Karl von Drais’s proto-bike left much to be desired. But as an objet d’art, it could not be gainsaid: with its curvaceous silhouette, its graciously hooped and spoked wheels, the machine cut a lovely figure.
The same was true of the inventions that followed Drais’s in the decades-long saga of refashioning and refining that brought us the modern bicycle. The bike that touched off a cycling craze in 1860s France was nicknamed “the boneshaker” because of the punishment its wrought-iron frame and ironshod wooden wheels inflicted on riders. The high-wheeler or “ordinary” or penny-farthing, the famous bike of the 1870s and early 1880s with a small wheel in the back and a huge one in front, was difficult to mount and dangerous to operate. Penny-farthing riders were prone to “taking a header,” flying headfirst over the handlebars. The name given to the breakthrough bike that ushered in the great cycling boom of the 1890s—the safety bicycle—testifies to the hazards of the models that preceded it. Yet like the Laufmaschine, the boneshaker had elegant looping lines, and the penny-farthing ranks among the most visually striking transport machines ever devised.
Today it may seem surprising that the bicycle was invented at all. Two inline wheels of equal size, with a chain drive on the rear wheel and a diamond-shaped frame—the classic safety bicycle form feels preordained, as natural as a human being with two arms and two legs. The bicycle’s geometry pleases the eye: the sweep of the handlebars, the flow of the tubing, the spindly lacing of the spokes. Your bike might be standing still, resting jauntily on its kickstand, but its streamlined contours give it the look of a thing in motion. Simone de Beauvoir described a bicycle whose appearance was “so lissome, so slender, that even when not in use it seemed to cut through the air.”
There is a kind of person who likes to look at bikes as much as he likes to ride them. I remember the first time I screwed a hook into the ceiling of a studio apartment and hung a bike lengthwise from its rear wheel. My ride to work was now also my décor, an artwork that dominated the small living space. At night, with the lights off, the rims and spokes would catch the glint of streetlamps from the sidewalk outside. When I spun the front wheel, reflections reeled across the wall like a disco ball light show.
I was not the first to take pleasure in this spectacle. Marcel Duchamp recalled the mesmeric effect of his famous readymade sculpture Bicycle Wheel (1913), a twenty-six-inch wheel mounted upright on a stool. “To see that wheel turning was very soothing, very comforting,” Duchamp said. “I enjoyed looking at it, just as I enjoy looking at the flames dancing in a fireplace.” For Adolf Loos, the architect and design theorist, the bicycle was a near-perfect piece of art, comparable in purity to the great creations of the ancient world. A Greek vase, Loos said, is “as beautiful as a bicycle.”
Bicycle design tells important stories. History speaks in the language of lugs and cranksets, in the height of bottom brackets, the shape of saddles, the slope of top tubes. The whimsical penny-farthing carries a lost Victorian world on its enormous front wheel. The Schwinn Sting-Ray, with its low-slung “wheelie” frame and elongated banana seat, is a piece of Americana as evocative of the funky late 1960s and early ’70s as bell-bottom jeans or Sly and the Family Stone’s Greatest Hits. Compare the slender, austere cruisers and roadsters that predominated in midcentury Europe to the American bikes of the period, with their bulging balloon tires and hefty frames with stylized motorcycle-style “gas tanks.” Clashing worldviews come into focus: on the one hand, an urban society in which bikes were utilitarian machines, integral to everyday life; on the other, a car culture that had relegated bicycles to the status of children’s playthings and surrogate motor vehicles, with “petro-fetishism” built into the bike frames themselves.
The main story the bicycle tells is one in which utility, simplicity, and beauty are indistinguishable. This is why Loos and other Bauhaus theorists, those wagers of war on ornament, hailed the bicycle as an embodiment of modernist ideals. The bicycle expresses the principle of “form follows function” with a transparency that is matched by few other human creations. To understand the workings of most machines, you must bury your nose in a user’s manual, then bury your head in the machine’s innards. A car conceals its mechanisms beneath covers and hoods and glossy paint and with the underside of its chassis. But the bicycle, wrote Roderick Watson and Martin Gray, “comes to us…naked”: “wheels, pedals, chain, crank and forks demonstrate their purpose and only their purpose, with scarcely an ounce of surplus matter.” The modern bicycle has just a few dozen functioning components, and they are in general durable and easy to maintain. The most vulnerable part of a bicycle, the tires’ inner tubes, can be repaired or replaced quickly and cheaply.
There have been many innovations in bicycle design and construction since the arrival of the safety bike. Derailleurs, disc brakes, titanium and carbon-fiber frames—innumerable new components and building materials have appeared on the scene. Whole new genres of bikes have come into the world. There are collapsible bikes that fold on hinges so you can carry them around like a backpack or briefcase; there are bicycle designs that you can download on open-source websites and print out on a 3D printer. But the basic shape, the classic safety bicycle silhouette, remains and reigns. Lewis Mumford wrote: “In every art there are forms so implicit in the process, so harmonious with the function, that they are, for practical purposes, ‘eternal.’ ” Mumford had in mind such things as the safety pin and the drinking bowl, whose antiquity would seem to justify the heady designation “eternal.” In historical terms, the bicycle is a new thing, but its form feels as fundamental and inviolable as any pin or bowl or Grecian urn.
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It begins with, what else, two wheels. In English, we call the machine a bicycle because of that pair of wheels—those twin “cycles,” a word derived from the Greek for “circle.” The writer Robert Penn has made the amusing observation that you could subtract nearly every component essential to the modern bike besides wheels—sprockets, chain, brakes, pedals—and you would still have a bicycle. (In fact, you would have stripped the thing back to Drais’s elemental Laufmaschine.) But the wheels are nonnegotiable: take those away and you won’t travel far.
The bike wheel has a combination of strength and lightness, stability and flexibility—qualities that distinguish the bicycle’s mechanism in general. Similar characteristics are exhibited by suspension bridges, to which spoked bicycle wheels have often been compared. Both bike wheels and bridges rely on the tensile strength of a network of wires; both have a weight-bearing capacity that seems improbable given their elegant, even delicate, appearance. The bicycle wheel is one of the strongest of all human contrivances, capable of supporting approximately four hundred times its own weight. In theory, a buffalo could pedal a bike without the wheels buckling under the load.
The first generations of bicycles had what were more or less carriage wheels, made of iron and wood, with fixed spokes built from those same materials. The wheels were heavy and rigid and not ideally engineered to withstand the burdens the bicycle and rider placed on them. As the wheel rotated, the weight was transferred to, and considerable stress placed upon, the spoke nearest the ground at the bottom of the wheel.
A breakthrough in wheel design came in the late 1860s and early 1870s, with the introduction of wire spokes. The conventional bicycle wheel of today has twenty-eight, thirty-two, or thirty-six spokes, which yank the hub and rim toward each other, keeping the wheel in a state of tension. These wheels can bear the load of cyclist and frame at any point on their circumference and tolerate pressure from different areas and angles: the stress that is exerted from underneath as the wheel moves over the road, torsional stress from the chain as it drives the rear wheel forward. In earlier stages of wheel development, spokes were threaded from hub to rim radially, but designers figured out that a tangential pattern—in which the spokes stretch out from the hub at angles in an overlapping configuration—made the wheel more resistant to warping. Also, tangential spoking is an eye-catcher. Lowrider bicycles, the extravagantly blinged and bedazzled customized bikes made famous by Latino cyclists in Los Angeles, feature as many as 144 spokes, often chrome- or gold-plated. Lowriders are perhaps the purest expression of bike-as-art-object, since in many cases they are bikes that cannot be ridden: the bottom brackets sit too close to the ground for the pedals to be turned. Like Duchamp, lowrider devotees look at the bicycle wheel and see fire, a metallic flicker and flare that they cannot resist stoking to maximum brightness.
You can gaze at the bicycle wheel; you can also listen to it. The faint click and purr of the rotating bike wheel is a sound as soothing as any in nature—as lulling as the trickle of water over stones in a riverbed. The bike wheel can make all kinds of music. A young Frank Zappa appeared on The Steve Allen Show in 1963, producing eerie tones by scraping at the spokes of a cruiser bike with a bass bow. (Zappa told an amused Allen that he’d been playing the bicycle for “about two weeks.”) Bike builders sometimes test wheels using tuning forks, plucking the spokes like guitar strings to determine if they sound the same pitches and are, therefore, correctly tensioned.
The process of adjusting spoke tension such that the rim will spin freely between the brake pads is known as “trueing” the wheel. For the philosophically disposed, the trued bicycle wheel embodies grander truths. The trued wheel plays notes in tune; the trued wheel obtains a Euclidean ideal. The spokes that stretch between the hub and the rim are engaged in a tug-of-war, each end straining against the other to hold the wheel in a perfect circle.
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Examine the bicycle and you will find more circles, and circles within circles. There are those Dunlopian circles, the tire and the inner tube, a circular sleeve cradling an air-filled ring. There are the various circular parts and pieces—clamps and washers, bolts and bushings—that make up the bicycle’s components and fix them in place. There is the chainring and the rear wheel sprocket, toothy disks along whose circumference the chain is impelled.
The development of the chain drive may rank as the most significant milestone in bicycle design, after Drais’s choice to arrange two wheels in a line. The first phase in the evolution came in the 1860s, with the invention of the boneshaker velocipede, which reconfigured Drais’s running machine as a pedal-powered device. This velocipede was a “direct-drive” vehicle: a rotary crank and pedals were affixed to the hub of the front wheel, and each rotation of the crank spun the front wheel around exactly once. To reach a higher “gear”—to make the bike travel faster with each revolution of the crank—the circumference of the wheel had to be increased. Thus the penny-farthing, whose gargantuan front wheel offered higher gear ratios but made cycling challenging and risky. A poorly taken bump in the road could result in the dreaded header—a plunge over the handlebars, a bruise, or a broken bone, or a broken neck, or a skull cracked like an eggshell.
These problems consumed the attention of mechanics and tinkerers for more than a decade. The solution came, at the end of the 1870s, with a new bicycle design that replaced the direct drive with a drivetrain transmission: a contraption that transferred the energy produced by the pedaling cyclist to the bicycle’s wheels via a chain. Earlier experimenters had tried connecting chain drives to the front wheel. But now the crank and pedal were shifted to the center of the bicycle, and the chain was looped from the crankset back to the rear wheel. When the pedals were pressed, the crank turned, the chain was activated, and the rear wheel was dragged forward, setting the bike in motion.
It was a simple and ingenious improvement. By running the chain between different-sized cogs—the larger chainring on the crankset and the smaller rear-wheel sprocket—the bicycle achieved a gearing effect: for every rotation of the pedals, the rear wheel revolved multiple times. This allowed the penny-farthing’s jumbo front wheel and miniature rear wheel to be discarded in favor of—at first, on the earliest model safety bikes—wheels of similar size, and, soon enough, equal-sized wheels, which made the bicycle easier to mount and operate. The front wheel could now be used simply to steer, a far less complicated arrangement than a steering apparatus that doubled as a pedal drive. In short, the chain drive was a great democratizer. It made the bicycle safer and simpler, transforming cycling from an activity dominated by sportsmen and daredevils into a mode of transportation open to more or less anyone—children, the elderly, the unathletic. Crucially, the invention of the safety bicycle refuted the theory—espoused by men, mostly—that cycling was beyond the ability of women, who were considered too delicate to brave the rigors of the boneshaker and the penny-farthing.
In technological terms, the bicycle’s chain drive was historic, a solution to conundrums pondered for ages by humankind in its quest for better tools. Hand-cranked devices had been in use since antiquity, but the safety bicycle’s drivetrain exploited the leg muscles, the largest in the human body, to create a motor of extraordinary efficiency. Once again that talismanic form, the circle, comes into play. The efficiency of the bicycle is based on the conversion of reciprocating motion—the up-and-down action of feet pressing pedals—into rotary motion, the dreamy circular revolutions of the pedals and crank. (In cycling slang, a rider with poor pedaling technique, or a rider whose technique slips as fatigue sets in, is said to be “pedaling squares.”) The result is energy-optimizing. As Robert Penn has written: “Cycling with regular pedals and cranks, our legs only push on the pedal for a small part of each pedal rotation: about 60 degrees. For the other 300 degrees of that revolution, the main muscles in that leg—hamstrings and quadriceps—are at rest, and able to absorb blood, carrying replacement energy.”
The other essential bicycle shape is the triangle. The classic diamond bicycle frame, codified in the 1880s with the invention of the safety bike, is in fact made up of two linked triangles. One of the triangles comprises the top tube, down tube, and seat tube; the second also incorporates the seat tube, from which the seat stays and chain stays angle back to the rear wheel axle. There are other, subtler triangles on the bike frame, formed by the front fork and chain stays, which connect, respectively, to the axles of the front and rear wheels. Structural engineers have long recognized that the triangle is the strongest geometric shape, resistant to deformation even when placed under great stress. A bicycle that has suffered a big crash may have a bent fork, wheels folded over like tacos, and various other ravaged bits and pieces. But the frame is likely to be intact. The underlying integrity of that frame configuration has allowed designers to incorporate progressively lighter materials—tubes made of aluminum or titanium or carbon fiber—without sacrificing stability. The triangles hold their shape.
Many other variables go into the making of frame geometry and the function of any given bicycle. The lengths and widths of the tubes, the angle of the steering axis, the positioning of the bottom bracket, the length of the wheelbase—these and other factors affect how the frame fits the rider, the speed at which the bike will travel, and how well it will handle. There have always been deviations in frame layout; the twenty-first century has brought radical new bicycle designs and novel frame shapes. But the diamond is the standard—most newfangled frames are, in truth, just variations on the theme. “It is unlikely that the diamond frame will ever be surpassed as a way to build a rigid-frame bicycle using joined tubes as a construction medium,” wrote the bicycle builder Sheldon Brown. “It is one of the most nearly perfect pieces of design known.”
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Machines with perfect designs, like those with imperfect ones, do not appear by magic. To build a bike, raw materials must be gathered and transported. The raw materials in, for instance, a road bike with an aluminum alloy frame may include aluminum, steel, iron, copper, manganese, magnesium, zinc, chromium, titanium, mineral oil, sulfur, carbon black, synthetic rubber, and natural rubber. These materials are mined from the earth or extracted from plants or cooked up in factories. During the manufacturing of the bike and its varied parts, further processes of refinement and treatment take place: grinding, smelting, hydroforming, extrusion, and vulcanization, among others. At each stage, waste and emissions are produced. Many of us take comfort in the knowledge that, by riding bikes, we are making an ethical and environmental choice. But bicycles do not float free from the realities of their creation: the resource extraction, energy consumption, and human labor involved in the manufacturing of a bike exacts a cost. The two-wheeler leaves a footprint.
Just how big a footprint is hard to say. The bicycle industry is global and byzantine. Most of today’s bicycles include parts manufactured in several different countries. Researchers who have attempted to write about the life cycle of bicycles have found it difficult to follow the supply chains to their origins—to pinpoint the open pit mine in Guinea or Ghana or China where the bauxite ore, the primary source of an aluminum bicycle frame, was originally dug up, or to identify where in the world the natural rubber in a bike tire was harvested. Suffice it to say, the extractive industries involved in the earliest stages of a bicycle’s life cycle have—to be generous—spotty environmental and human rights records, and it is sentimental to suppose that bikes, by virtue of being bikes, arrive in this world clean and green. Nor should we be naïve about the conditions under which bicycles are assembled in factories. Journalists have uncovered labor abuses in the bicycle industry, including the exploitation of child bike factory workers in such places as Cambodia and Bangladesh.
The historical record is darker still. We need look no further than John Boyd Dunlop and the pneumatic rubber tire. In the standard version of bicycle history, the tale of Dunlop’s invention is narrated—as in the Prologue to this book—as a technical and mercantile triumph, the final breakthrough that set the late-nineteenth-century bike boom in motion. But that story fails to trace the rubber in the countless tires and inner tubes back to the source: to rubber plantations in the Amazon basin and to the “red rubber” terror in the Belgian Congo, where millions died harvesting latex from Landolphia owariensis vines. In Brazil, one person perished for every 150 kilograms of rubber reaped; in Congo, the figure was one death for every ten kilograms of rubber. “If you were one of the millions all over the world who started riding a bicycle in the 1890s ‘bicycle craze,’ you may have coasted on a cushion of Congo rubber,” writes the historian Maya Jasanoff. The connection between the turn-of-the-century boom and the humanitarian and ecological infamies perpetrated by European powers extends to at least one more natural resource: asphalt, mined by exploited laborers in the English colonial territory of Trinidad, and used to lay the smooth surfaces over which so many European and American cyclists rolled their wheels.
This grim record may temper our enthusiasm for the Great Man version of bicycle history, with its pantheon of illustrious European inventors and innovators. Their achievements are impressive nonetheless. Alongside Drais and Dunlop and the safety bicycle pioneer John Kemp Starley, cycling historians enshrine such names as Pierre Michaux, a Parisian blacksmith believed by some to have produced the first boneshaker velocipedes, and Eugène Meyer, whose work was crucial to the development of the high-wheeler. There are contributors to bicycle anatomy at the molecular level. A key figure is Jules-Pierre Suriray, the Parisian bicycle builder who patented the ball bearing, that “atom of the Machine Age,” essential to the operation of not just bikes and cars but everything from fishing reels to air conditioners to computer hard drives to the Hubble telescope and the Mars rover.
The record is muddled by the usual disputes about provenance. Historians debate whether credit for the invention of the pedal bike should go to Michaux or to various fellow travelers in the mid-nineteenth-century French bicycle trade. (In recent years, a new scholarly consensus has formed around Pierre Lallement, a French mechanic who moved to Connecticut and was granted the first U.S. patent for a pedal-driven velocipede in 1866.) There is also the controversial case of Kirkpatrick Macmillan, a blacksmith from Dumfries, Scotland, who, according to some sources, invented a pedal bicycle, with a rear wheel drive powered by treadles and rods, in the 1830s.
The story of the bicycle’s evolution is also industrial history, a tale of innovative products and the companies that brought them to market. Bike booms and boomlets have been spurred by the introduction of new kinds of cycles: tricycles in the 1880s, racing bicycles in the 1930s, derailleur and BMX bikes in the ’60s and ’70s, mountain bikes in the ’80s, the e-bikes of the present day. Connoisseurs of bicycle components and equipment have their own canons of beloved parts and hallowed parts makers. The mystique surrounding such producers of bike components as Campagnolo, Shimano, and SRAM, and the zealousness with which bicycle “gearheads” choose sides among and pledge allegiance to these brands, is a subject worthy of its own tome.
But it is wrong to view the bicycle as a thing that has been handed down from on high, bestowed on the world by heroic individuals and visionary manufacturers. The bicycle is a populist project, the result of grassroots innovation and an exchange of knowledge that runs in all directions. A defining quality of the bicycle’s form is its openness to hacks and interventions, to rejiggering and retrofitting. The simplicity and legibility of the bicycle’s mechanism has brought out the mad scientist in millions. A curious child with a decent set of wrenches can strip a bike down to the bearings and build it back up again, adding bells and whistles if so inclined.
The culture of popular mechanics that began in the late nineteenth century was initially dominated by cyclists who discovered how simple and enjoyable it was to jury-rig their safety bikes. “There are two ways you can get exercise out of a bicycle,” wrote the English humorist Jerome K. Jerome in 1900. “You can ‘overhaul’ it, or you can ride it.” The vast numbers of hybridized bikes and bike-like machines—bikes you can pedal through the air, bikes you can ride across the water, bikes you can lie down in as if on a daybed—reflect the ease with which the bicycle can be modified and the conviction that bikes are, that bikes should be, infinitely accommodating of new forms and alternative functions. In 1886, an American journalist mocked the compulsion to create bicycle crossbreeds: “When we finally get a full-rigged bicycle, with its steam engine, mainsail, spinnaker, and all the other appliances suggested or invented, we shall have a new means of suicide which cannot fail to become popular.”
Altered bikes have altered the course of historical events. The bicycle first arrived in Vietnam as a tool of empire: a favored form of transport and recreation for colonial officials in French Indochina and a cash cow for French manufacturers, who for years operated with something close to a monopoly in Vietnam. But the locals soon adopted the bicycle to their own ends, including anti-colonial resistance and guerrilla military actions against French and, later, American occupiers. The Vietnamese used bikes both to transport explosives and as explosives, concealing bombs in the hollows of seat tubes or top tubes. A secret American military report issued in May 1966 noted the practice with alarm: “Sometimes the bicycle itself is the instrument of death, its hollow tubular frame packed with plastic explosive and the timing devices located under the saddle. Terrorists ride the bicycle into the area, lean it up against the building to be destroyed, set the fuse, and walk off.” In subsequent decades, “bike bombs” have become familiar features of asymmetrical warfare and struggles against occupying powers. In the so-called war on terror, American forces in Iraq and Afghanistan were frequently targeted with explosives hidden in and attached to bicycles.
The impulse to strip down and soup up has given the world new kinds of bikes and new ways of biking. The origins of the modern mountain bicycle can be traced to a group of cyclists in Northern California in the 1970s who altered vintage bikes so they could go riding up and down Mount Tamalpais, a famous peak in Marin County. The cyclists renovated prewar Schwinns—reinforcing the frames, replacing the handlebars, adding new tires, gearing, cranks, and brakes—to create “klunkers” capable of navigating footpaths that sloped nearly thirteen hundred feet through rugged terrain on the face of Pine Mountain, one of Mount Tamalpais’s foothills. The nickname the riders gave to this trail, Repack, paid tribute to their down-and-dirty handiwork: the cyclists’ screaming descents left their coaster brakes squeaking and smoldering, necessitating the frequent repacking of brake hubs with grease.
Eventually one of the top Repack racers, Joe Breeze, began to design, build, and sell his own line of purpose-built mountain bikes. The bicycle industry soon followed suit. By some measures, the mountain bike is the most popular model of bicycle to reach the public since the safety. Its sturdy construction, low gear ratios, shock-absorbing suspension systems, and easy handling have made it a favorite of millions of riders who will never get anywhere near an off-road trail.
Today, DIY experimentation remains a fundamental aspect of bicycle culture, and a foundation of bicycle subcultures. The developing nations of Asia, Africa, and Latin America, where cycles serve a wide variety of utilitarian functions, are hotbeds of customization: overhauls that turn two-wheelers into three- and four-wheeled cargo vehicles, novel designs that deploy pedals and drivetrains as power generators to run tools and electrical systems. In certain bohemian enclaves, bicycle building is a political act and an expression of dissident identity. The “freak bike” or “mutant bike” movement, a punk- and anarchist-affiliated scene concentrated in American cities, is dedicated to the construction of bicycles of odd shapes and sizes, scrapped together from scavenged parts. Freak bikes give physical form to the ideals of recycling and reuse. The freak bike’s battered, proudly low-tech look makes an anti-consumerist statement—spurning the gleaming machines that roll off the factory floors of mass manufacturers and the upmarket artisanship of bespoke bike builders—while treating the bicycle as a punk art object, a medium of absurdist play and display. No one who has shared a city street with an armada of mutant “tall bikes”—seven-foot-high contraptions with “ape hanger” handlebars and three diamond frames welded together in a vertical stack—will think the same way about the art of the vélo.
Those who have no interest in or aptitude for grimy bicycle bricolage can nonetheless derive a unique kind of hands-on pleasure from a bike. The click of the grip shifter as you change gears. The action of the calipers as your brake pads clench the rims. In an age dominated by alienating frictionless interactions with digital devices, the bicycle offers a throwback, a reminder of the tactile satisfactions of machine age technology. There is poetry in the workings of the bicycle’s components. “To consider the endless perfection of the chain, the links forever settling about the cogs, is a perpetual pleasure,” wrote the literary scholar Hugh Kenner. “To reflect that a specified link is alternately stationary with respect to the sprocket, then in motion with respect to the same sprocket, without hiatus between these conditions, is to entertain the sort of soothing mystery which…you can study all your life and never understand.”
The most important bike component is the engine, otherwise known as the rider. The essence of the bicycle’s design lies in its uncanny fusion of machine and human being. Builders of high-end custom bicycles use computer programs and mathematical formulas to provide fine tailoring, precisely fitting the bike frame to a person’s frame. But even the rider of a scrap-heap junker can experience the strange sensation of becoming one with the bike. In “Le Vélocipède” (1869), the poet Théodore Faullain de Banville pictured the cyclist as “a new animal /…Half wheel and half brain.” Flann O’Brien, one of the great bicycle bards, described “people in these parts who nearly are half people and half bicycles…[who] get their personalities mixed up with the personalities of their bicycle as a result of the interchanging of atoms of each of them.” These chimeric metaphors may be the closest we can get to capturing in words the feeling of a particularly free-flowing ride, when your body and being—shoulders, hands, hips, legs, bones, muscles, skin, brain—seem to be inseparable from the strong but supple bicycle frame. At such moments, to conceive of the bike as a vehicle is perhaps not quite right. It may be more accurate to think of it as a prosthesis. Ideally, it is hard to say exactly where the bicyclist ends and the bicycle begins.