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Gravity Bikes

(Or Everybody Hurtles Sometimes)

Technically Dan Verity’s Gravity Racer is not a bicycle, although it’s made from one. In historical bicycle classification terms, and quite literally; it’s a bone shaker.

Propelled by the relentless power of our planet’s gravity these miniature monsters hurtle to speeds in excess of 60mph. It’s a relatively inexpensive sport to get into; all you need is an old BMX, a full face motorcycle helmet and leathers to ride, some welding skills. And the side of a mountain.

Starting life as a BMX, the frame is stripped and flipped upside down before being reassembled without cranks, chain or sprockets. Bars, foot pegs and vestigial fairings are welded on. Optional lead weights give the planet a little something extra to get its teeth into.

Starts are crucially important, as with other descent sports such as luge and toboggan. As speeds increase aerodynamic drag and courage become the major inhibiting factors.

 

 

 

Off-Road. Chapter introduction.

The mountain bike may be cycling’s newest arrival but Off Road riding is as old as cycling itself.

In the beginning the very first cyclists were also the very first off-roaders. Early cycling on rough unmade tracks was ‘off-road’ because roads as we know them simply hadn't been invented. It was the surge in popularity of bicycles and tricycles which created the demand for smooth surfaces and the subsequent widespread adoption of tarmac as a road surface material. Gliding along the newly surfaced roads early cyclists could have had little inkling that one day the roads would become so congested by other kinds of traffic that cyclists would want to escape again to the dirt.

Though road riding has always been the most visible side of cycling there has always been an off-road element to it; cyclocross racing (which is as popular as ever), grass track racing, and cycle speedway all have long histories. The first half of the twentieth century was the heyday of a particularly British and uniquely intrepid breed of cycle tourist for whom the lack of a road was little obstacle. Their bikes were nothing special, certainly nothing like what would be consider an off-road bike today and ‘rough stuff’ or ‘pass storming’ was the off-road journey you made to connect the road sections of a route. Carrying or even dragging the poor bike over inappropriate terrain was all part of the ‘fun’. The Rough Stuff Fellowship still exists today.

In the 1970s, a group of Californian cycling enthusiasts astride heavy American cruisers began an anarchic series of race meetings in Marin County. Their bikes had just one brake (a barely adequate coaster or ‘pedal back’ brake) and moderating the dirt-track descent created enough heat to burn off all the grease in their rear hubs. At the end of each run down the mountain they had to be stripped and repacked with bearing grease. The course, and the race, passed into legend as The Repack.

The reason that these bikes had such a performance advantage over anything that had gone off-road before was the wheel size; the uniquely American 26 x 2.125” Imperial standard. Introduced to the market by a handful of US manufacturers including Schwinn around 1932 and used on millions of bikes over the years it had a large air volume and correspondingly large footprint which rolled well in the rough and held its grip in the corners. The first few Repack races required the use of a pick-up truck to carry all the bikes back up the hill after every run. The brilliant innovation which transformed these bikes from mere ‘Clunkers' into ‘Mountain Bikes’ was the adoption of new technology which had started appearing on bicycles being imported from Europe. Multiple chain rings and long arm derailleurs provided a super wide gear range which allowed the riders to pedal back up the mountain. Tandem derived cantilever brakes paired with motorcycle levers provided greatly improved braking performance. Before long bespoke frames were being designed and built and lighter components added. At the New York cycle show in 1981 the solitary mountain bike on display was swamped by the agents of Far Eastern bicycle manufacturers wielding measuring equipment.

As mountain bikes increased in popularity and entered volume production, high prices dropped and components started to improve in quality. To many in the industry the new bikes were an abomination, but to the bicycle buying public these machines were a revelation. People accustomed to the traditional choice of heavy roadster or five speed ‘racer' could suddenly afford a pretty light, super-tough bike with plenty of gears, powerful brakes and the flexibility to move briskly both on and off-road. In some countries Mountain bikes, designed to withstand the rigours of off-road riding, managed to achieve the impossible – make city cycling cooler and more fun than it had ever been before. A phenomenon had been born which was set to change the world of cycling profoundly and forever.

In the thirty years since mountain bikes first appeared in the shops we have seen a complete transformation of the breed. Back then mountain bikes had steel alloy frames and forks, geometry virtually unchanged from those first Repack Clunkers, cantilever brakes, friction shifters controlling 15 gears. None of it was dedicated equipment; the brakes came from tandems, other parts were lifted from the touring bike or BMX parts bin. Everything has changed since then; steel frames have all but disappeared from the middle and upper end of the market, replaced by aluminum, titanium and, increasingly, carbon-fibre composite monocoque. Instead of five sprockets on the back wheel we now find up to ten (at the time of writing!). Cantilever rim brakes disappeared in the mid nineties, replaced by more powerful linear-pull brakes which in turn are slowly being sidelined by disc brakes. Modern controls are so well integrated that riders can shift, brake, adjust front and rear suspension and even saddle height on the move whilst keeping both hands firmly on the bars and pointing in the right direction.

Suspension has transformed the way we ride, available from 80mm travel on forks for lightweight XC bikes to over 300mm travel on the rear of some big-hit free-ride bikes. Modern mountain bikers now have to comprehend things like platform-valving, high and low speed compression and rebound damping, pivot location, floating shocks, actuators, lock-out, oil viscosity and axle paths, but the biggest transformation of all is how the breed has fragmented. Once upon a time a mountain bike was a mountain bike was a mountain bike. Now we a have a broad spectrum of types to fill every imaginable niche; from indestructible twelve inch travel free-ride to superlight cross-country race bike. Fully rigid single-speed, 4X, All-Mountain, Back Country, Hard-Core Hard-Tail, Soft-Tail, Dirt-Jump or fully loaded Expedition Mountain Bike. Trail Bikes, Trials Bikes, Mud Bikes, even dedicated Snow Bikes. Individually unique, but each one a Mountain Bike.

The constant search for performance advantage has made mountain biking a hot-bed of cycling technological development. As a result materials, technology and processes developed for mountain bikes have all found their way into every other kind of bike. Whether you ride a mountain bike or not - if your Road Bike, Street Bike or Folding Bike is less than ten years old you’re using technology which was developed to cope with the rigours of dirt riding. All of our bikes are more durable thanks to sealed bearings.

The evolution of the off–road bike is far from over. In an ironic twist the twenty six inch tyre introduced all those years ago, the very thing which made the invention of the mountain bike possible may now be under threat of extinction. The recently introduced ‘29er' has been a huge success, widely adopted by mountain bikers for its ability to roll over trail imperfections better than its 26inch grand-daddy. But it hasn’t stopped there. A few manufacturers are now promoting yet another standard, the inbetweeny, best-of-both-worlds 650b (what Americans call the 'twenty-seven-and-a-half-inch').

Technological advancement has been a major factor in the history of mountain biking it’s important to remember that the reason off-road riding is so popular today, indeed the reason it exists at all is down to one three letter word. The Repack racers could not have imagined that in the quest for fun they would have such a monumental influence on so many people's lives and transformed a whole industry.

Without knowing it, they changed the world.

 

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