Cycling: Armstrong fears carnage on first cobbled stage on Tour for six years

This year's Tour de France will cover 3,600 kilometres [2,236 miles], including some of the most fearsome climbs in the Alps and the Pyrenees. It's one of the toughest Tours in years, and yet perhaps the moment the peloton has been fearing most will arrive at about 4.30pm today, in between one bleak post-industrial town in southern Belgium and another in northern France. This is when the Tour hits the cobbles. Lance Armstrong predicted last week that there would be carnage and he wasn't exaggerating.

Riding on cobbles might not sound as difficult as all that, but these are far from the perfectly ordered rows of neatly carved elongated ovals you might find in any city centre seeking to give itself an olde-worlde air. Rather they will be great broken chunks of stone, 15 or 20 centimetres long and seven wide, and clustered in poorly formed, half-broken patterns across muddy, wind-lashed country back roads: as one British magazine once poetically put it, "tossed randomly from the sky by an angry cycling god".

In fact, not even the cyclists dare to use these roads very often. The professionals visit these lost, rural lanes of what the French call pavé just once a year, in the Paris-Roubaix one-day Classic in April. Dubbed the "Hell of the North" or "The Race That Time Forgot", just three or four of cycling's top 20 riders are brave enough to risk their careers and take part in a 260km event that invariably contains a welter of punctures, broken bikes and crashes.

Physically it can exact a huge toll. Most top Roubaix riders reckon it takes at least two days for their hands to stop trembling from the constant, bone-shaking vibrations the race has inflicted on them, three days for the pain to start to go. British specialist Roger Hammond, who has taken third and fourth in Paris-Roubaix, once said it takes around a week for him to recover fully.

Paris-Roubaix regularly ends careers. Mark Madiot, who is a double Roubaix winner, broke his hip in 1994 and never rode again. When Johan Museeuw broke his leg during the 1998 Paris-Roubaix so much dirt from the road infected the wound it was touch and go whether it would have to be amputated. He eventually recovered, and won the Paris-Roubaix in a downpour for a third time in 2002, so plastered in mud he was barely recognisable.

When the Tour director, Christian Prudhomme, announced last October at the 2010 Tour presentation that the race would take in some seven sections of Paris-Roubaix pavé for the first time in six years, the favourites' usual polite smiles gave way to stunned silence.

"There will be a lot of crashes for sure," warned Bjarne Riis, the team manager of two top contenders, Andy and Frank Schleck. "If all hell breaks loose, as it will, there will be a lot of time differences."

The reason why the Tour contenders are so worried is that riding over such terrain calls for very unusual bike- handling skills, more suited to former cross-country world champions such as Hammond than three-week stage racers.

"Dry weather makes for better racing and rather than riding on the top of the pavé, where it's safer in the wet, you're best off in the gutters," Madiot said. "But when it's dry there's dust too, so it's hard to see more than a few metres ahead. You mustn't follow the next guy's wheel too closely like you would in other races. If you do that on the pavé and he crashes, then you've had it. You've got to keep your distance, watch the whole line ahead of you. Above all, anticipate."

Following Prudhomme's announcement, almost all of the top Tour favourites almost immediately began elaborate preparations. Alberto Contador , who has never ridden any of the so-called "Cobbled Classics", visited the area in April on a bike specially designed to resist the vibrations of the cobblestones. Bradley Wiggins, one of the few top contenders who has taken part in Paris-Roubaix, has checked out the cobbles twice in April and again last month – because the "wet and dry conditions make it so different".

Other teams, such as Rabobank, are refusing to confirm their overall leader until the stage is over. Will it be the double Tour of Spain winner Denis Menchov or his promising young Dutch team-mate Robert Gesink, both equally inexperienced on such terrain? "We're not saying," sports director Adri Van Houweligen said. "It's better off waiting until the stage is over."

Lance Armstrong, the only rider vying for yellow in Paris to have ridden in the 2004 Tour, has been uttering dire warnings about the stage for some time.

Most of them – consciously or not – will strike home at Contador, who is certainly viewing his first experience of racing over cobbles with some trepidation. "It's not so much the cobbles themselves, but the approaches that could be dangerous," Contador said. "Everybody wants to be in front, everybody wants to stay out of trouble. Somebody's bound to go down."

Cyclists from Contador's part of the world have been protesting about the cobbles for over half a century. The Tour came this way in 1959, when the race had another top Spanish favourite, the eventual overall winner Federico Martin Bahamontes.

For over 150 kilometres of the 217 in that 1959 stage the Tour riders covered a never-ending succession of pavé, something Spanish sports daily Marca said snootily in its report from the race, "was inhuman in this age and day, when we can all ride along nice smooth motorways.

"Why bother with these cobblestones which stick out so much, round here the locals call them 'priests hats'?"

Fifty-one years on, if most of the Tour peloton will have similar feelings about today's stage, at least one of Britain's eight Tour riders is looking forward to hammering over the pavé of northern France.

"I love riding on the cobbles, I get upset that I can't usually do races like Paris-Roubaix," HTC-Columbia's Mark Cavendish said. "Me, I'm not nervous about it at all." Cavendish, though, will be very much the exception that proves the rule.

How they will cope with cobbles

Teams will make a number of changes today to combat the effect of the cobbled streets:

Wheels Tyre pressure will be lowered from the usual 100 psi to 65 psi. This means less risk of getting caught between cobblestones, so less risk of punctures. Wheels will be fatter by up to three or four millimetres.

Handlebars These will be raised by a centimetre. Some riders use cyclo-cross brake levers on the bars while others add double handlebar tape round the bars to decrease vibrations.

Help from teams Mechanics are posted at the end of cobbled sections with spare wheels and tyres as the following team cars may be delayed.