Priceless Porte a boon for Froome at Tour de France

Australian Richie Porte's bike racing skills appear to know no bounds on the Tour de France, and on Thursday included breaking the rules on an epic 18th stage to the Alpe d'Huez.

Team Sky rider Porte has been demonstrating his faith towards yellow jersey holder Chris Froome throughout the race but on the 172.5 km trek from Gap to the legendary summit had to go beyond the normal call of duty.

Froome, who began the day with a 4min 34sec lead on second-placed Spaniard Alberto Contador, felt the first signs of hypoglycemia early on the second climb of the 13.8 km ascent to the legendary summit.

By the time he was approaching the 5 km to go mark, the Kenyan-born Briton's arm was in the sky desperately asking for assistance.

With no feeding allowed in the final 29 kilometres, Froome was in trouble -- but Porte, whose job is to set a pace for Froome that is not too hard but which can do damage to rivals, was on hand.

The Tasmanian dropped back to the Team Sky car, collected a handful of sugar-rich power gels and rode back up the rode to feed his team leader.

Froome and Porte were both sanctioned with a 20sec penalty but in the grand scheme of things it was irrelevant. Froome is now 5:11 ahead of two-time winner Contador, who had even bigger trouble trying to match Sky's pace before finishing nearly a minute behind the pair and 4:15 behind stage winner Christophe Riblon.

"I was really going into a little bit of a sugar low then," explained Froome.

"I asked Richie to go back to the car... and he just gave me some gels to get me to the finish.

"I don't know if it helped me with 5 km to go but it was really good to have Richie there, he did a fantastic job."

It was yet another solid day in the saddle for Porte, on a day Sky expected to fight off attacks from a number of rivals, and illustrated once more why the British team have to try to keep him in their ranks.

Froome, who at times on the final climb was falling back off Porte's wheel due to the pace, virtually admitted that if he was absent from the race the Australian would be the man to beat.

"He's the second best GC (general classification) rider in this race... he's shown several times that he is one of the best GC riders in the world," said Froome.

The winner earlier this year of Paris-Nice, Porte has been considered a huge talent for some time although winning between winning France's third-biggest stage race and the Tour de France there is a huge gulf.

Porte, who had been in second place overall after Froome's victory atop Ax-Trois-Domaines on stage eight before tumbling down the standings a day later, has sacrificed any personal ambitions on the 100th Tour to help Froome win.

A day after saving his energy in the stage 17 time trial, his contribution for Froome prompted Colombian Nairo Quintana to attack and go on to move up to third place to threaten Contador's virtual runner-up place.

"I had a good day," said Porte.

"We were able to take a bit more time out of Alberto (Contador) and I'm happy to see Quintana's moved up onto the podium. I think he really deserves it and I think it's going to be a good battle now."

He added: "I've been pretty good the whole Tour. I had an easy day yesterday and obviously the GC guys had a full-gas day."