MUR DE BRETAGNE, France >> Sometimes in cycling the bike can be the rider's biggest enemy.Tour de France contenders Tom Dumoulin and Romain Bardet both lost significant time in the overall standings after spokes on their wheels snapped near the uphill end of Stage 6 on Thursday.Both title hopefuls were left behind by the rest of the top riders as they increased the pace hunting for the win that finally went to Daniel Martin of Ireland.