French champion Thomas Voeckler took the home nation's fifth stage win of the Tour de France, attacking his breakaway companions halfway up the Port de Bales and soloeing down the winding descent into Bagneres-du-Luchon.
However, there was controversy behind as Andy Schleck lost his yellow jersey after unshipping his chain while attacking on the day's last climb. Alberto Contador (Astana), the defending champion and the man who takes over the race lead, profited from the mechanical problem.
The Luxembourgeois's fortunes reversed in one moment. After making a big acceleration with three kilometres of the final climb to go, Schleck appeared to be distancing his rivals.
Then his chain was off; the back wheel twitched violently, he ground to a halt and after failing to get it back, the 25-year-old had to take a spare bicycle and start his fierce pursuit.
Just minute earlier, there had been similar dissembling to yesterday's fourteenth stage. Schleck had moved away with Contador, Sanchez, Menchov and Van den Broeck only to slow the pace significantly, allowing the distanced riders to get back on.
Ahead, Thomas Voeckler had already struck out alone and was putting time into his closest challenger, Alessandro Ballan (BMC Racing Team). The former world champion would be joined by Aitor Perez (Footon-Servetto) near the climb's summit.
The Bbox Bouygues Telecom proved the strongest man from a ten-rider move which escaped at the 93km mark, after two hours of fast and vigilant racing.
Alongside Voeckler, Ballan and Perez, it also included Johan van Summeren (Garmin-Transitions), Serguei Ivanov (Katusha), Sebastien Turgot (Bbox Bouygues Telecom), Lloyd Mondory (Ag2r-La Mondiale), Luke Roberts (Team Milram), Brian Vandborg (Liquigas-Doimo) and Francesco Reda (Quick Step).
Press play to watch Stage 15 highlights
The yellow jersey chases
With the yellow jersey chasing hard behind, Contador, Sanchez and Menchov looked around but appeared to resume a regular pace as they pushed towards the summit of the Port de Bales.
Crossing the climb 20 seconds down, with Jurgen van den Broeck in tow, Schleck descended the narrow and corkscrewing road to the finish as quickly as he dared, albeit to no avail.
All with their own reasons for distancing Schleck, Contador, Sanchez and Menchov did not hesitate on the 19-kilometre run down, sweeping up several of the day's breakaway members on the precipitious road down.
Eighty seconds after a jubilant Voeckler kissed the French tricolore jersey in celebration of his second Tour stage, Ballan edged Perez for second place.
Behind, breakaway member Lloyd Mondory (Ag2r-La Mondiale) claimed fourth at the head of the Contador group. Crossing the line in seventh, the defending champion rode into the yellow jersey and a brewing storm about sportsmanship and decorum at the Tour.
The clock ticked down behind. While Schleck carved through the final corners in Bagneres-de-Luchon with great urgency, he ultimately lost the maillot jaune by eight seconds.
The Luxembourgeois was visibly angry as he headed off to the Saxo Bank team bus after the finish. If the last few days have been characterised by mind games and kidology, the gloves are now off for the last two stages in the Pyrenees, with the race precariously placed.
Meanwhile, Bradley Wiggins (Team Sky) lost almost seven minutes to the favourites, dropping to 23rd place overall.
Tour de France, stage 15: Pamiers - Bagneres-de-Luchon
1. Thomas Voeckler (Fra) Bbox Bouygues Telecom 187.5km in 4-44-51
2. Alessandro Ballan (Ita) BMC Racing Team at 1-20
3. Aitor Perez (Spa) Footon-Servetto at same time
4. Lloyd Mondory (Fra) Ag2r-La Mondiale at 2-50
5. Luke Roberts (Aus) Team Milram
6. Francesco Reda (Ita) Quick Step
7. Alberto Contador (Spa) Astana
8. Samuel Sanchez (Spa) Euskaltel - Euskadi
9. Denis Menchov (Rus) Rabobank
10. Brian Vandborg (Den) Liquigas-Doimo all same time
12. Andy Schleck (Lux) Saxo Bank at 3-29
13. Jurgen van den Broeck (Bel) Omega Pharma-Lotto at same time
23. Lance Armstrong (USA) RadioShack at 4-08
48. Bradley Wiggins (GB) Team Sky at 9-35
104. Geraint Thomas (GB) Team Sky at 26-04
113. Mark Cavendish (GB) HTC-Columbia at 28-49
141. Steve Cummings (GB) Team Sky
145. Daniel Lloyd (GB) Cervelo Test Team
151. David Millar (GB) Garmin-Transitions
170. Jeremy Hunt (GB) Cervelo Test Team at same time
General classification after stage 15
1. Alberto Contador (Spa) Astana 72-50-42
2. Andy Schleck (Lux) Saxo Bank at 8secs
3. Samuel Sanchez (Spa) Euskaltel-Euskadi at 2-00
4. Denis Menchov (Rus) Rabobank at 2-13
5. Jurgen van den Broeck (Bel) Omega Pharma-Lotto at 3-39
6. Robert Gesink (Ned) Rabobank at 5-01
7. Levi Leipheimer (Usa) Team RadioShack at 5-25
8. Joaquim Rodriguez (Spa) Katusha at 5-45
9. Alexandre Vinokourov (Kaz) Astana at 7-12
10. Ryder Hesjedal (Can) Garmin-Transitions at 7-51
17. Nicolas Roche (Irl) Ag2r-La Mondiale at 12-34
23. Bradley Wiggins (GB) Team Sky at 17-44
31. Lance Armstrong (USA) Team RadioShack at 40-31
72. Geraint Thomas (GB) Team Sky at 1-33-12
149. Steve Cummings (GB) Team Sky at 2-47-18
151. Mark Cavendish (GB) HTC-Columbia at 2-49-43
157. David Millar (GB) Garmin-Transitions at 2-57-19
163. Daniel Lloyd (GB) Cervelo Test Team at 2-59-45
166. Jeremy Hunt (GB) Cervelo Test Team at 3-01-58
Points classification: Alessandro Petacchi
King of the Mountains classification: Anthony Charteau
Young rider classification: Andy Schleck
Lance Armstrong and RadioShack
Thomas Voeckler wins: Tuck yourself in young man
Andy Schleck: Not happy at time loss
Alberto Contador takes the race lead
Tour de France 2010: Latest news
Wiggins at 2010 Tour: "I haven't got it"
Basso wins Tour's acceptance; podium spot next goal
Contador versus Schleck: A game of seconds
Can Cav win without Renshaw?
Hesjedal pushing his way to the Tour's top
Renshaw disqualification overshadows Cavendish's win
Charly Wegelius pulls out of Tour
Did Armstrong own a stake in Tailwind Sports, or not?
Cavendish in a 'must win' situation for Tour's green jersey
Millar rides through pain barrier to make time cut
Roche alongside Tour's top men ahead of Pyrenees
Wiggins to aim for Tour de France stage win?
Dan Lloyd battles on in Tour despite groin strain
Tour de France 2010: Stage reports
Stage 14: Riblon hangs on in Pyrenees to give France fourth stage win
Stage 13: Vino returns to top of Tour after doping ban
Stage 12: Rodriguez wins as Contador attacks
Stage 11: Cavendish bags third stage win but lead out man kicked out of Tour
Stage 10: Cavendish bags third stage win but his lead-out man is kicked out of race
Stage 10: Paulinho claims narrow stage victory on Bastille day
Stage nine: Casar wins stage as Schleck and Contador go head-to-head
Stage seven: Chavanel wins stage and takes overall as Thomas drops out of Tour's white
Stage six: Cavendish makes it two as Tour hots up
Stage five: Cavendish wins his first stage of Tour
Stage four: Petacchi wins into Reims
Stage three: Hushovd takes dramatic win; Thomas second on stage and GC
Stage three live coverage: As it happened
Stage two: Comeback man Chavanel takes victory in Spa
Stage one: Petacchi wins in Brussels as bunch left in tatters
Prologue: Cancellara pips Martin to win
Tour de France 2010: Photos
Stage 14 photo gallery
Stage 13 photo gallery
Stage 12 photo gallery
Stage 11 photo gallery
Stage 10 photo gallery
Stage nine photo gallery
Stage eight photo gallery
Tour 2010 wallpaper
Stage seven photo gallery
Stage six photo gallery
Stage five photo gallery
Stage four photo gallery
Stage three photo gallery
Stage two photo gallery
Stage one gallery
Prologue photo gallery
Tour de France 2010: Videos
Stage 14 video highlights
Stage 13 video highlights
Stage 12 video highlights
Stage 11 video highlights
Stage 10 video highlights
Stage nine video highlights
Stage eight video highlights
Stage seven video highlights
Stage six video highlights
Stage five video highlights
Stage four video highlights
Stage three video highlights
Stage two video highlights
Stage one video highlights
Prologue video highlights
Tour de France 2010: Race guide
Tour de France 2010: Cycling Weekly's coverage index
Official start list, with race numbers
Brits at the Tour 2010
Tout team guide
Tour jerseys: What they are and what they mean
Brits in the Tours: From Robinson to Wiggins
Tour de France 2010: Pictures
Tour team presentation, Rotterdam
Tour teams take to the cobbles: Photo special
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