By Julien Pretot LAC DE PAYOLLE, France (Reuters) - Briton Stephen Cummings powered away on the Col d'Aspin to claim a second career Tour de France stage win as overall contender Thibaut Pinot cracked in a seventh stage that ended in chaos on Friday. As Team Dimension Data rider Cummings celebrated his stunning solo win, back down the road the inflatable arch marking 1km to go deflated and slowed down the bunch, sending fellow Briton Adam Yates crashing. Belgian Greg Van Avermaet retained the overall leader's yellow jersey at the end of the 162.5-km trek L'Isle Jourdain. More...