Tour de France cyclists were facing a new ordeal on Tuesday with the fourth stage being the longest of the race and featuring several testing cobbled sectors.

A spectacular crash on Monday's third stage robbed the Tour of six riders, including the man who had started the day wearing the race leader's yellow jersey, Fabian Cancellara.

Around 20 riders went down in the crash and although Cancellara got up and soldiered on to the finish, he went straight to hospital where X-rays showed he had fractured two vertebrae.

South African Daryl Impey, who also finished the stage, fractured his collarbone, Tom Dumoulin of the Netherlands dislocated his shoulder while Australia's Simon Gerrans, Russian Dmitry Kozontchuk and William Bonnet of France, who caused the tumble, were all also forced to abandon.

Tuesday's 221.5km stage is the longest of the race and takes in seven sectors of cobbles amounting to more than 13km, while there is also the possibility of thunderstorms and rain at some point along the course.

Chris Froome, the 2013 champion, starts the stage in yellow having put time into all his main rivals over the previous two days.

Last year he crashed out on the cobbled fifth stage with a broken wrist after hitting the deck three times over two days.

But he did so before even reaching the first cobbled sector and the Briton will be in unchartered waters over the pave.

- Classics undercurrent

Froome, though, insists that he and his Sky teammates are ready for whatever the course throws at them.

"I'd like to just set the record straight for last year that it wasn't the cobbles that put me out of the race. I didn't even see a cobble in last year's Tour! I didn't make it that far," said the 30-year-old.

"With the Classics undercurrent that we've got in this team I'm going to be more than protected come the cobbled stage.

"We've been out there, looked at the cobbles, I'm quite happy riding them and quite looking forward to that stage."

Last year Vincenzo Nibali took a great stride towards winning the Tour on the cobbled stage as he finished third and gained around two and a half minutes on his main rivals.

But that was in terrible conditions and should the course stay largely dry on Tuesday, it won't be quite as tough.

He also starts the stage 1min 38sec behind Froome and would need a similar performance to last year to start clawing back time.

Alberto Contador lost 2min 45sec to Nibali on last year's cobbled stage but he is closest to Froome, at 36sec, of the main overall contenders.

Nairo Quintana is in the most precarious position as he is already almost 2min off Froome and at just 50kg, his physique is not suited to riding cobbles.

He may simply be racing to limit his losses on Tuesday.

The yellow jersey could also change hands for the third day in a row as German Tony Martin is just one second behind Froome in the overall standings and six more riders are within 36sec of the lead, including cobbled specialists Greg Van Avermaet and Peter Sagan.
Source: AFP