Beachy Head in East Sussex has some of the tallest cliffs in the country; hence its dark reputation as a destination for those attempting suicide. But this weekend the location will play host to a less lethal type of kamikaze fun.

More than 150 competitors from Germany, Sweden and America as well as up to 20,000 spectators are expected to descend on the stretch of coastline for the British leg of the Go Fast Speed Days World Cup, the first International Gravity Sports Association championship to be held in Britain.

Haven’t heard of gravity sports? Well, you’re not alone but if the organisers are to be believed it is set to become the next big thing in the world of extreme sports. Like many such high adrenaline activities it can trace its roots back to California in the 1970s when young daredevils and surfer dudes sought new ways to have as much fun and generate as much speed as possible without the use of an engine.

Today those eclectic techniques have been distilled into separate hair-raising disciplines that see competitors clad in motorcycle leathers and crash helmets descend steep roads at speeds of up to 80mph on a variety of “vehicles”. Unlike Formula One overtaking is common – as are crashes.

Disciplines include street luge, which replaces ice with tarmac as competitors shoot along the street in a supine position on a wheeled platform; downhill skateboarding where contestants use what are described as “skateboards on steroids” to race down steep, twisting roads; and gravity bikes, the insanely fast and furious sport that is basically downhill freewheeling on modified bikes.

“It’s all about 9.8 metres per second squared - in other words, gravity,” says Tom Worsley, a British street luger and chairman of the UK Gravity Sports Association. “You can’t blame an engine or a team, it’s just you and your skill in making the most of gravity.” Worsley, a mechanical technician from Oxford, is one of a growing band of gravity sports fans who says you can’t beat the buzz of “bombing down a hill while lying on your back on an overgrown skateboard”.

The sport isn’t for the fainthearted and injuries are common: two years ago a practice run ended in an encounter with a fence that left Worsley with a shattered tibia.

This is hardly encouraging as I prepare to take part in a trial run down part of the 1.5km descent that will be used during the championship. I will be the “monkey”, or co-pilot on a gravity bike, and it will be my job to help maintain the balance on the “sidecar” as we career down the twisting hill.

My pilot and instructor is Tom Evans, a professional gravity sportsman who travels around Europe and North America competing in events. “Crouch down low and keep your feet off the ground,” he tells me as I step onto the bike – a triangular piece of aluminium with three wheels, one of which is connected to a set of handlebars and brakes and is used for steering. “Keep low to reduce the wind resistance and hold on.” “Where?” I ask, realising how small and insubstantial the bike is.

“Er, anywhere. You might find yourself holding on to me while we go round corners – either way just lean into them.”

I get on and flatten myself so that I’m as low as I can be, just inches away from the road surface that will grate me like cheese if we come off. Almost before I realise it, Evans has started pushing the bike and jumped onto it.

We’re off.

The rumbling and vibration are intense as we begin to pick up speed. Ramblers along the roadside stare, and their faces say it all as we tear by: “What the hell was that?”

My visor fogs up and we come into a bend, speed increasing all the time. I lean into it as instructed. With no suspension, every dip and change in the road surface jolts us violently. The noise of the wind is deafening and I begin to feel real fear as the tarmac rushes by inches from my nose.

For the championship - which sees heats take place on Saturday followed by racing proper on Sunday - the road will be closed to traffic and surrounded by bales of hay as a safety precaution while competitors from as far afield as South Africa and Australia take part. Most of these are privateers who build their own vehicles although some come as part of teams such as VXR Gravity, backed by the car manufacturer Vauxhall, which aims to promote British engineering talent in schools and colleges. More typical is Peter Eliot, an Oxford graduate and now highflying financial adviser in the City, who is coming out of retirement to try to win the street luge championship on home soil.

As we walk back up the hill dragging the gravity bike with us and still shaking partly from the adrenaline rush, I congratulate Evans on his mastery of the gravity bike.

“You’re welcome,” he says, slipping off his gloves and helmet. “It wasn’t too bad, was it, considering that I’d never ridden a gravity bike before. Downhill skateboarding is my gravity sport but that was fun, wasn’t it?”

How to do it

What Gravity sports

Why Because this is the fastest you will ever travel without an engine

When The UK Gravity Sports Association (UKGSA) runs a number of events throughout the year. This weekend the British leg of the world championship is taking place at Eastbourne in East Sussex

How There are several different categories. The most popular are street luge, downhill skateboard and gravity bikes

Cost Membership of the UKGSA costs £40pa and covers deposits for hill hire and insurance. Equipment costs vary - a street luge can be built for £250 while a top gravity bike can cost up to £3,000

More info www.ukgsa.org, www.gofastspeeddays.com, www.gravity-sports.com