Following his second-place performance behind teammate Evan Huffman the day before, Britton went on a solo breakaway that saw him survive to the lower slopes of Mt. Baldy during stage 5 and win the most courageous rider jersey for the race's queen stage.
Before the stage started, Britton said his team would try and stack the breakaway like it did the day before with himself and Huffman.
"Ideally, getting any guys up the road and having a crack at it as long as possible is the plan," he said, and when the race took off from Ontario for 125.5km of mountainous racing, Britton and Huffman infiltrated the large breakaway that formed almost immediately.
Britton held firm as the group began to whittle itself down, and he attacked alone with about 35km left to race. Team Sky's Peter Kennaugh joined him, but he soon lost contact and folded back into the group behind.
From there, Britton pressed on alone for what would turn out to be a long afternoon of pain.
"Oh man," was Britton's only response when asked how bad that effort hurt after he spent most of the day before off the front as well.
"The 15k after the last KOM was pretty god awful," he said. "It was pretty windy up there, so that was just awful. I just tried to stick with one steady rhythm."
As Britton tapped out tempo on Glendora Mountain Road, the peloton that included all of the general classification favourites caught the remnants of the break and set their sights on the Rally rider.
"I thought maybe if I had three minutes going into the base of the last climb I'd be OK, but with less than that it was going to be real tight," Britton said. "It was like 1:15 into the base, and I thought, ‘Oh, man, this is going to be really close now'."
It wasn't that close, as the bunch caught Britton almost immediately after the race turned toward the final climb. As the pain in Britton's pedal stroke showed, eventual stage winner Andrew Talansky (Cannondale-Drapac) drove the bunch past.
Britton wasn't entirely finished, however, as he latched into the back of the group and then moved forward again to work for teammate Sepp Kuss, who had also clung to the elite group of climbers.
As Britton eventually dropped out of the group, Kuss picked up the Rally baton and launched an attack or two of his own.
"I was of course a little bit excited there at the bottom, but I didn't want have any what ifs," Kuss said. "I felt good so I figured I might as well follow some moves. None of the attacks were super long, but after a while they were a bit draining."
Kuss eventually faded after his attacks, but he held on for 10th place, coming in 56 seconds behind Talansky as the first non-WorldTour rider on the stage.
"I didn't have much left there in the end; I was kind of running on fumes, but when it's steep like that, you can kind of grind into the hill, so it almost makes it easier to stay on the gas," he said. "But I'm pretty satisfied, and Rob had a super awesome ride and stuck it to the bitter end."