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BAGNERES-DE-LUCHON, France -- The gloves have come off at the Tour de France.

Andy Schleck was fighting mad after dropping his chain during a tough climb Monday and then losing the overall lead when defending champion Alberto Contador unabashedly sped ahead to take the yellow jersey.

"He can be nervous for the next days ... this gives me anger," said Schleck, vowing revenge. "I'm not the one who will get chased any more, I'm the one who chases. That's a big difference."

The episode highlighted the often-unclear etiquette of cycling's greatest race, where the wearer of the yellow jersey is conferred almost queen-bee-like respect -- and taking advantage of mishaps out of his control is frowned upon.

The breach came on a day when France's Thomas Voeckler came out of a long breakaway to win the 15th stage from Pamiers to Bagneres to Luchon, finishing a 116.5-mile trek that included the merciless Port de Bales climb in 4 hours, 44 minutes, 51 seconds.

Contador, who gained time while Schleck was putting his chain back on and during a high-speed downhill to the finish, crossed 2:50 back in seventh, while Schleck came in 12th -- 3:29 after Voeckler.

After more than two weeks and 1,800 miles of racing, the two-time champion from Spain leads Schleck by merely 8 seconds. Spain's Samuel Sanchez is third, 2:00 back.

With Schleck only 31 seconds ahead going into Monday's stage and big Pyrenean climbs ahead promising a shakeout, tensions were certain to escalate. The two self-avowed friends had spent one calmer day in this Tour discussing a recent vacation getaway they had had together.

The friendship is now apparently on hold.

"We're only here in a bike race, so let's leave it that way," Schleck said after a long pause, when asked if he and Contador were still friends. "I think everybody can make his opinion about the race today."

Schleck hit the accelerator in an attack about 2.5 miles from the top of the Port de Bales, but his chain came unfurled. For a few seconds he pedaled on in disbelief before stopping to fumble with his chain as Contador and other top riders sped by.

At the finish, Schleck swatted back reporters and gritted his teeth in anger. Contador said such woes are part of the sport, and insisted he didn't know about his rival's troubles right away.

"Those are the circumstances of the race," he said. "I knew there would be a debate after that, but I attacked before I knew he had a problem with his chain, and I was already ahead when I knew it."

"I understand he's disappointed."

He wasn't alone. Contador heard nearly as many boos as cheers when he donned the coveted yellow shirt for the first time this year at the awards ceremony after the stage.

"I'm not going to cry over the yellow jersey," Schleck said.

Lance Armstrong knows about the unwritten race rules -- and two instances in the Pyrenees stand out during his seven-year reign of domination at the Tour.

In 2001, he slowed down after top rival Jan Ullrich crashed on a fast descent from the Peyresourde pass. Two years later, the German and other riders waited for Armstrong after a fan's outstretched handbag snagged his handlebars -- hurtling him to the asphalt on the ascent to Luz-Ardiden. Armstrong went on to win both of those stages.

Another difference with Monday's outcome was that both of those instances involved crashes, where the Tour's unwritten code is somewhat clearer about not taking advantage of the yellow jersey's struggles.

Schleck himself benefited from Contador's sense of fair play earlier this Tour. In Stage 2 into Spa on July 5, the Spaniard waited when Schleck went down in one of an array of crashes on rain-slickened roads.

"Alberto was one of the guys who waited for me in Spa, so that was really 'chapeau' (hat's off)," said Schleck. "Today was a different story, a different scenario."

As the July 25 finish on the Champs-Elysees in Paris looms, the competition and nerves in the pack are heating up -- but sportsmanship should still take precedence, Schleck said.

"Today, you know, everybody is in panic, they see already the Eiffel Tower. I would not have taken advantage of the situation," he said. "It's not up to me ... but for sure these guys don't get the fair-play prize today."

"I wouldn't want to take the jersey like that."

Armstrong said Monday's case wasn't so clear cut.

"It's better to wait, but this is different because this was the last climb of the race, and the race was really on," said Armstrong, who is 31st overall, 40:31 behind Contador.

There was also some question about whether Schleck might have caused the chain to come off by shifting gears during a rapid acceleration.

Voeckler captured his second Tour stage in as many years -- he also won solo in Perpignan last year -- and gave France its fifth stage victory at this year's race. The BBox Bouygues Telecom rider held the yellow jersey for nine days in 2004, until Armstrong took it off him.

With two more grueling Pyrenean stages and a time trial still on tap, Schleck and Contador said they didn't think Monday's 39-second turnaround will affect who wears yellow home.

Tuesday's 16th stage, the third day in the Pyrenees, is one of the toughest this year -- taking the riders 124 miles from Bagneres-de-Luchon to Pau. The course goes over the major climbs of the Col de Peyresourde, Col d'Aspin and Col d'Aubisque, but the highlight will be the first of two crossings of the legendary Col du Tourmalet.

Schleck vowed Monday's episode would become a big motivator.

"I've got fire in my belly," he said. "The race is not finished, and I will take my revenge in the next days."