The first stage after the rest day proved to be a tough battle on the climbs and of the elements, with high temperatures making the stage even more difficult.
Porte finished the stage in tenth place, and gained time on all of his GC rivals except overall leader Chris Froome (Sky), who was the only rider to match the Australian’s tempo in the final kilometre of the stage.
Solo stage winner Ilnur Zackarin (Team Katusha) came from a breakaway, managing to out-climb Jarlinson Pantano (IAM Cycling) and Rafal Majka (Tinkoff).
Behind them, the battle of the yellow jersey group kicked into gear on the final Hors Categorie climb.
Porte waited for the right moment to attack and picked it well, with Froome the only rider who could match his pace to the finish line. Porte gained time back on his other riders and now sits in sixth, four minutes and 27 seconds behind the yellow jersey of his former team-mate.
“I really want to be on the podium so they’re the moves that you have to pull. I felt strong today and I’m happy with how it all went,” said Porte.
“I’m with BMC Racing Team now and I’m riding for myself so it’s a bit different to the role I’ve had before. But I’m enjoying it, taking it day by day. The team has put some confidence in me and I’m happy with how today went. I know there are three more hard stages to come until Paris. So we’ll just take it day by day.
“I spoke with the Sports Directors this morning and they said just use your head and if you feel like it, attack them. I have to anyhow. The tempo was not so fast there and it was a good time to get a gap there. They chased hard I suppose so it’s a good sign.”
Tonight’s stage is a 17km uphill individual time trial from Sallanches to Megève. This stage offers Porte further opportunities to claw back the one minute and 34 seconds which separates the Australian from third overall, Adam Yates (Orica-BikeExchange).
“I quite like uphill time trials so I think it’s a crucial one tomorrow. I know I need to have a good time trial and take some time. I think I’ve shown today that I’m climbing well so I take confidence out of today.”
Porte's BMC team-mate Tejay van Garderen lost time on the climb and slipped out on the top ten on the general classification. While it’s back to the drawing board for van Garderen to work out why he doesn’t have the form he hoped for, he will work in support Porte over the final stages of the race.
“In other years I’ve crashed or been sick, but this year I don’t know, it’s not responding. There’s really no excuse, I wish I had one but I don’t know. I guess I’m going to have to sit down with our performance team and see what we did in the build up,” said van Garderen.
“I’ve raced against a lot of these guys before in other races and I’ve been able to be there with them, and for some reason this year it’s not happening.
“I think I’ll use the TT tomorrow as a recovery day, as much as I can anyway. And then I’ll do what I can to help Richie. Maybe if the legs rebound and I’m down enough on time they might let me sneak into a breakaway and go for a stage win.
“Richie, from what I heard on the radio, had an amazing ride so we’re really going to put everything behind him.”