was won by Ángel Sarrapio (), who had been in a breakaway with Jean-Claude Bagot () during the stage. Pedersen kept the race lead, while Pelier used bonus seconds on the road to move ahead of Roche into second place in the general classification. On stage 11, a 12-man breakaway reached the finishing town of Bordeaux together. Rudy Dhaenens () escaped from the group from the finish. On the finishing straight, he was almost caught by the fast approaching Hermans and just held on to take the stage victory. Hermans would later say that the public announcer had aided Dhaenens' victory by warning him of Hermans over the PA system. Pyrenees Following a train transfer from Bordeaux to Bayonne at the foot of the Pyrenees in the morning, stage 12 led the riders over to Pau. The stage featured five mountain passes, with the first-category rated Col de Marie-Blanque at the end, before a descent into the finishing town. Several attacks occurred over the first part of the stage, each covered by riders of . At around from the finish, Hinault raised the pace on the ascent of the Col de Burdincurutcheta, forcing other contenders to chase back on, such as Herrera. Others, such as Roche, Fignon, and race leader Pedersen, dropped behind and would lose a lot of time by the end of the stage. Shortly before an intermediate sprint after , Hinault told his teammate Jean-François Bernard to accelerate, and the two, accompanied by Delgado, made the bridge to a lead group containing Eduardo Chozas (). These four riders then broke clear at the front, before Chozas lost contact about later. Bernard, the work for his team leader done, fell back another down the road. Delgado and Hinault worked well together to extend their advantage to the chasers, where LeMond, bound by team tactics, was unable to give chase himself. According to Delgado, Hinault clearly wanted to make time for the overall classification, and without any negotiating between the two, he gifted the stage win to Delgado. LeMond managed to break clear of the rest of the chase group with Herrera, but still arrived in Pau 4:37 minutes behind Hinault, who was now leading the race overall. After the stage, LeMond was overheard telling his father: "Goddamnit, Dad, I am going to finish second again!" Other favourites lost even more time: Robert Millar () finished 11th, 5:31 minutes