They saw beach-bum surfers getting a kick out of riding big "breakers" and wanted some excitement (and an adrenalin rush) of their own. So they took to the hills, particularly those in northern California, which had numerous off-beat tracks to whizz down. But a problem soon presented itself: their bikes were not up to bumpy rocks and uncovered roots - bits kept falling off. So they began to make adjustments to toughen up the frames and the wheels of their road bikes.
Twenty years on, mountain biking has grown into big business beyond the wildest dreams of those first few experimental riders. Last year, 2 million bikes were sold in Britain, of which 95 per cent were mountain bikes. Compare that with mountain bike sales a decade ago - which numbered just a few thousand or so each year - and the rapid growth of the sport has been nothing short of phenomenal.
"They've become so popular because you can take them almost anywhere," said Bruce Johnson, of British Mountain Biking, which is affiliated to the British Cycling Federation (BCF). "Traditional bikes can normally only withstand riding on roads while mountain bikes can go on dirt tracks, old tow-paths, hills, virtually anything.
"The success is also down to the recent trend towards healthy outdoor living as well as the fact that anyone from about the age of 12 to 70 can ride them. Families can hitch bikes on to roof-racks and can go off on riding holidays together - and they don't have to stick to boring roads."
Most mountain bikes, which range in price from as little as pounds 150 for basic models to up to pounds 3,000 or so, are bought by those who want to go on leisurely weekend rides. However, there are now regular weekend competitions up and down the country for the more serious bikers: race-standard bikes begin at around pounds 350. Most races, which are often broken down into age categories, are organised by local bike shops or centrally by the BCF.
British mountain bikers are considered - along with the Americans and the French - as among the best in the world. Caroline Alexander won the European Championships for Britain last year and is taking part in the Atlanta Olympics, the first time mountain biking has been included in the Games (another indication of its popularity). Alexander is aware of the challenge Atlanta will present. "You're close to your limit for two- hours plus: the hammer goes down from the gun and you're at your maximum heart rate all the way. It's one of the toughest sports. Only cross-country skiing and marathon running can compare with it."
There is also a whole new mountain biking subculture. In rather the same way snowboarders have broken away from mainstream skiers and developed their own alternative "grunge-style" clothing on the slopes, the trendiest mountain bikers dress totally differently from traditional cyclists.
Instead of wearing the type of skin-tight Spandex worn by Tour de France riders, the look is baggy shorts or jeans; T-shirts; backwards baseball caps or wool hats. These mountain bikers tend not to enter competitions; they would rather - in the spirit of the Californian pioneers - head off for the hills and find a new, even more exciting track. For any rider keen on making it a regular pursuit, the most important accessory is a safety-approved helmet - you will fall off, no matter your skill level.
Bikes these days are technologically advanced: titanium frames, front and back suspension, disc brakes and specially designed tyre treads to deal with different terrains and weather conditions.
But it can all get a little bit confusing for the beginner, especially when brochures explaining the various features slip into (almost incomprehensible) biking jargon: "Load-distributing spears", "butterfly gussets", "weld beads", "rim sidewalls" and "four-bar linkage full-suspension". One brochure described its bike frames as having "oval-ised seatstays for durability and torsional rigidity so they resist brake flex, yet include taper gauge butting to shave weight and absorb shock".
Several mountain biking magazines have sprouted up recently, and run regular features helping to decipher the jargon and explain the pros and cons of the latest innovations. They tend to be very much consumer-led, concentrating on what bikes are the best value for money.
So what is the best way to go about buying a mountain bike? Bruce Johnson had some advice: "Be very careful about mail order catalogues. Sometimes bikes that are described as 'mountain bikes' aren't strong enough for proper hill cycling. The best thing to do is to go to your local shop and explain whether you intend to use the bike for casual excursions or if you are going to go on tough tracks and bash it about. It's important to get a bike that suits you."
Bruce Johnson's seven points to look out for in choosing a mountain bike
Lower-range bikes priced between pounds 150 and pounds 200 do not have strong enough suspension to cope with hills: they tend to lose their spring very quickly. You get suspension that's tough enough for most leisurely hill riding in the pounds 200-350 range. The suspension you need for competitive racing is in the pounds 350-450 range. Bikes priced above this will have excellent suspension and the best will have both front and back suspension; cheaper bikes just have it on the front.
They range in price from about pounds 18 to pounds 26 each and are normally between 1.7in and 2.2in wide. The wider the tyre, the better it is for cross-country riding. Thin tyres suit flatter terrains. You can get different sized treads - the deeper and wider treads are suited to more muddy conditions.
The best, and the most expensive, are made of titanium and carbon, which is light and strong. Middle-of-the-range bike frames are made of a mixture of aluminium and steel; not quite as light as the titanium and carbon ones. The cheapest are made of quite heavy steel.
Most bikes will have between 18 and 24 gears. Gears are very important on steep hills and it helps to have as many as possible. In some gears, riding is less physically exhausting than walking.
For cross-country riding, it's important to have wide, padded saddles for comfort. Only the best competitive downhill racers go for narrow saddles so that they can shift their body weight about more easily when taking sharp corners.
The more expensive bikes - from about pounds 400 upwards - will have disc brakes, which allow them to stop more suddenly and with more control. Most other bikes will have traditional cantilever brakes.
Helmets should always be worn. They range in price from about pounds 25 to pounds 70. Downhill competitive racers should wear full face helmets, which look like motor-bike helmets and usually cost more than pounds 200. Competitors also wear elbow, knee and shoulder pads, goggles and gloves. Beginners really need only wear gloves if they are riding sensibly.
British Cycling Federation
National Cycling Centre
Manchester, M11 4DQ
Telephone 0161-230 2301
Cycling Touring Club
69 Mead Row
Godalming, Surrey GU7 3HS.
Telephone 01483 417217
Mountain Biking UK
30 Monmouth Street
Bath, BA1 2BW.
Telephone 01225 442244
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