But as Biffle pulled his No. 16 Ford into his pit stall for his final stop at Kansas Speedway, Biffle wanted four tires to finish the race. His crew chief, Greg Erwin, wanted to change only two.
Biffle overruled him and stuck four fingers out the window as he rolled to a stop -- and it cost him dearly.
Stewart's crew changed only two tires on his Chevrolet, enabling Stewart to leave the pits ahead of Biffle and the other leaders and then win the third race in NASCAR's Chase for the Cup championship playoff.
With his victory in the Price Chopper 400, Stewart -- a two-time champion who formed his own team this year -- climbed one spot to fourth place in the 10-race Chase and slashed his deficit to 67 points from 106 behind leader Mark Martin.
Martin finished the race seventh in his Hendrick Motorsports Chevrolet on a crisp, clear day in front of 100,000 at the 1.5-mile Kansas Speedway oval.
Reigning champion Jimmie Johnson, Martin's teammate, had the strongest car for part of the race and led 53 of the 267 laps. But he finished ninth and remained second in the Chase, 18 points behind Martin. Johnson had arrived in Kansas only 10 points back.
And Juan Pablo Montoya kept the third spot in the Chase, 51 points behind Martin, with a fourth-place finish in the race.
Stewart's win was his fourth of the season and his first in the Chase, which continues next Sunday with the Pepsi 500 at Auto Club Speedway in Fontana.
"We had a real good car on two tires," Stewart said, adding that it was "a no-brainer" to change two on the final stop because passing was difficult and track position was paramount.
"It's the perfect scenario for us right now," Stewart said. "This team is going to have some momentum going into California next week."
Four-time champion Jeff Gordon, another Hendrick driver, passed Biffle after the final restart and tried to catch Stewart. But Gordon finished second and is now seventh in the Chase, 103 points behind Martin.
"As I got closer to [Stewart], my car just really started getting tighter and tighter," Gordon said. "As long as he didn't make any big mistakes, I wasn't going to catch him."
Biffle, a Roush Fenway Racing driver who has gone a year without a victory, led the most laps in the race, 113, before his ill-fated tire decision on the final pit stop.
"I know what I did was wrong," said Biffle, who won the Kansas race in 2007. "I know I made a mistake. But we're sure excited to be running good again, especially going to some tracks we like, like California."
Johnson, the race's defending winner, is trying to capture an unprecedented fourth consecutive championship, and he appeared to gain momentum after a dominant win at last week's race in Dover, Del.
"I hate losing points, I felt like we had a shot to win the race," Johnson said. But he added that "it's just way too early, for myself, even to start worrying about" the Chase standings. "It's only three races in."
Martin, the 50-year-old veteran trying to win his first title, agreed. "I don't think we should be getting all hyped up about the tally right now," he said, adding that his Chevy "just lacked a little bit being able to get up there and contend for the win."
Nine of the race's top 10 finishers were Chase contenders; the exception was eighth-place David Reutimann.
Dale Earnhardt Jr., NASCAR's most popular driver who has struggled most of the season, led 41 laps early in the race in another Hendrick Chevy after starting second behind Martin.
But a costly miscue in the pits started a string of problems that ruined Earnhardt's day.
On his first pit stop, Earnhardt's crew failed to place a lug nut on his left rear wheel, forcing him back to the pits and putting him one lap behind the leaders. He finished 36th.
"It's frustrating," he said. "We had a real fast car. We were running as fast as the leaders."
Earnhardt now has gone 50 races since his last victory, at Michigan in June 2008, and before that he had a 76-race winless streak. So Earnhardt now has only one win in his last 127 races.
(BEGIN TEXT OF INFOBOX)
*--* RK. DRIVER PTS. BK. 1. Mark Martin 5,551 -- 2. J. Johnson 5,533 18 3. Juan Montoya 5,500 51 4. Tony Stewart 5,484 67 5. Kurt Busch 5,460 91 6. Denny Hamlin 5,452 99 7. Jeff Gordon 5,448 103 8. Greg Biffle 5,437 114 9. Ryan Newman 5,387 164 10. Carl Edwards 5,386 165 11. Kasey Kahne 5,361 190 12. Brian Vickers 5,301 250 *--*