Kyle Busch and Tony Stewart are known for their racing success and explosive tempers.
Most every problem on the track is followed by a profanity-laced rant, a tantrum and in Busch's case a meltdown right in the car that has at times prevented him from making a strong finish. Then came the sulking and scowling. If they even bothered to give interviews, the answers were usually short and snippy.
It was boorish behavior, but tolerated. Nothing was going to change NASCAR's two biggest bad boys.
Until, that is, they changed.
Busch and Stewart seem to have mellowed this season. That was never more apparent than Sunday at Las Vegas Motor Speedway. Both had a chance to win, and neither did.
Busch was done in first by a flat tire, then a blown engine. He was running second when he got his flat, had to stop for a new tire and disagreed with his crew's decision to change only two and not all four. That's where Busch would typically unload on crew chief Dave Rogers, working himself into a hysteria that could have derailed his race.
Instead, Busch simply scolded Rogers. He then calmly offered advice when a caution moments later gave them a chance to salvage the setback. A blown engine 10 laps later, however, ended his day at his home track, where wins mean the most to him.
As Busch climbed from his disabled car, the race streaming around him, viewers braced for his reaction. If he didn't stomp away from the cameras, his interview would probably be a bitter one.
Then, for the second time in two days, he was a total pro.
"I've been blowing tires, mowing grass, knocking walls down and setting balls of fire down the backstretch in both races this weekend," he said. "It might be good just to get out of here and come back and try again next year."
Then came Stewart, who led a race-high 163 laps and had the field covered at one of only two active tracks where the two-time champion has never won a Sprint Cup race. After falling short in the Daytona 500, then losing because of a late caution a week earlier in Phoenix, he finally seemed headed to Victory Lane.
Then a rare mistake on pit road -- he pulled the air hose tangled in his fender out of his stall as he sped off -- brought a damaging penalty. He went from the lead to 23rd place. He drove his way back to 16th and needed a two-tire decision by crew chief Darian Grubb on the next caution to reclaim the lead.
But there was one more pit stop, and that tire strategy meant he'd have to change all four the next time. Only the entire field had watched him pull away with just the two tires, and most every crew chief now planned to copy that strategy.
That final four-tire stop was a long one. But because so many others took two, Stewart found himself behind Carl Edwards and Juan Pablo Montoya on the final run. Stewart could catch only Montoya and settled for second.
He was, as expected, hot on his team radio and warned of an immediate discussion on how they'd just given away a race for a second straight week. But he bottled that anger when he climbed from his car, and all the public saw was a disappointed driver dealing with his third loss in three weeks.
"It kills me to throw a race away like that," he said. "When the emotion dies down, we'll look back and say it was a great weekend, but man, it does not sit good right now."
And that was about it.
There was no explosion, no belittling of reporters' questions and no need to tiptoe around either driver.
So what's happened to NASCAR's two firecrackers? And, more important, will it last?
For Busch, the answer could simply be that he's growing up.
He got married during the offseason, which perhaps gave him some serenity. He's also settling into his second year of owning a Truck Series team, and last year's rocky first season taught him how to deal with sponsorship issues, financial problems and a new level of responsibility.
But he's also finally aware of the popular opinion that the only thing that's prevented Busch from winning a Sprint Cup title is Busch.
All those outbursts on his team radio, all that on-track bumping and banging with competitors and all those times he lost focus in the race car really hurt only one person -- Busch.
It seems as if the light is finally on and Busch is trying his hardest not to be his own worst enemy anymore.
Stewart's not as simple. He was always able to succeed despite himself, relying on his immense talent to overcome his outbursts and moodiness. But it's been five years since his last championship, and the wins are far harder to come by at this stage of his career.
His many business ventures have made him a team owner, track operator, race promoter and just about everything else involved in professional racing, and that's created a desire to keep things smooth and stable.
Stewart now sees that life is much easier when he's not making it hard on everyone around him. Plus, he turns 40 this year and is aware of the impending milestone. Still single, he longs to have children and create his version of the perfect family. He's tired of riding that roller coaster -- charming and funny one minute, brooding and mean the next -- and understands he's the only one who can change that.
It's far too early in the season to declare either driver a truly changed man, but both are certainly trying. And while everyone might miss their entertaining explosions, both will probably find their new approach will make life easier both on and off the track.