PRA-LOUP - Nairo Quintana repeatedly tested Tour de France leader Chris Froome as German Simon Geschke won Wednesday's 161km 17th stage from Digne-les-Bains to Pra Loup. Quintana first accelerated inside the opening 50km, again on the imposing Col d'Allos and then had two more goes on the final 6.2km climb to the finish.

However, Froome responded every time and crossed the line just behind the Colombian to keep his 3min 10sec lead in the race for the yellow jersey. However it was a disastrous day for some of their rivals on the 2015 Tour's first Alpine stage. Tejay Van Garderen, who started the day third, quit the race with 70km remaining following an illness that had seen him dropped by the peloton. Alberto Contador, who was virtually up to fourth at that stage, crashed on the 15.9km descent off the Col d'Allos ahead of the final climb and lost 2min 17sec to Froome. He also ended the day fifth as Froome's Sky teammate Geraint Thomas overtook him by 6sec in the overall standings. Spaniard Alejandro Valverde is up to third, although he dropped 7sec in the final 500-metres and now sits at 4min 09sec.

Reigning champion Vincenzo Nibali continued to improve and is now seventh, just 25sec behind sixth-placed Robert Geesink. Having suffered terribly in the Pyrenees, he kept up with the overall contenders until the final 500-metres where he lost 15sec. He is 1min 30sec back from Thomas in fourth and can realistically aim to overtake the Welshman with three more Alpine stages to come.

But all that was happening a long way behind Geschke, who was part of an initial 28-man breakaway. The 29-year-old attacked solo inside the final 50km and was never caught. American Andrew Talansky crossed the line second at 32sec with Colombia's Rigoberto Uran third at 1min 01sec. There could have been a different result but for Frenchman Thibaut Pinot crashing on the final descent.

The 25-year-old was second at the time and chasing Geschke. Although he was still second after remounting, he'd lost his confidence and had also given up four places by the time he reached the foot of the long and tricky descent. Unable to make up the time he'd lost, he finished fourth at 1min 36sec. After a fierce start to the day's racing, it took 60km for a breakaway to stick and when it did, it contained 28 riders.

Most surprising, though, was the presence of two of Froome's Sky teammates, including Australian Richie Porte. The Tasmanian later waited for Froome to help his team leader up to the top of Allos, although his influence was short-lived. By the time the break formed, Van Garderen was already in trouble and lost two minutes to the peloton.

Although his BMC team helped him regain contact, an acceleration from Contador saw him distanced once and for all. With 70km left he climbed off his bike -- his Tour over, as was that of world champion Michal Kwiatkowski 35km later. Geschke attacked from the breakaway group with the imposing Col d'Allos looming and Pinot counter-attacked 4km from its summit.

Nibali's Astana team took up peloton pace-setting duties and when the Italian himself burst away, only Froome, Quintana, Valverde and Contador could follow. But once over the top and onto the tough descent of Allos, Contador crashed, losing contact with the other overall contenders.