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The NASCAR Sprint Cup schedule is one of the longest stretches for competitors in all of professional sports with 36 races. But many of the drivers not only participate in those events and the two non-points races over the course of the year, they also race in other series as recreation.

Why do they do it? Reasons vary slightly, but mostly it comes down to one thing: these men simply love to race and compete. While racing in the Cup series certainly feeds that hunger, drivers accustomed to the rigors of the Cup schedule like to get away from it all from time to time and race in a different environment.

It's a chance to go back to racing the way they used to. It's a chance for a new challenge. It's a chance to race against the best in a different environment. It's a chance to compete against the best, in a different arena.

For these drivers, that is enough to make it worth the extra effort.

On Jan. 30, six full-time Cup drivers -- AJ Allmendinger, Jimmie Johnson, Bobby Labonte, Jamie McMurray, Paul Menard and Juan Pablo Montoya -- will compete in the Rolex 24 at Daytona. Michael Waltrip and Marcos Ambrose raced a 24-hour sports-car event in Dubai earlier this month. Tony Stewart and Kasey Kahne have often competed in the Chili Bowl and Stewart raced in a series of events in Australia this offseason. Robby Gordon is an off-road regular, finishing eighth in the Dakar Rally earlier this month and winning the SCORE Trophy Truck and overall championship in 2009.

Why do they do it?

"I'm a race car driver, it's what I love to do," Stewart says of racing in other series. "This is my job, obviously, in the Cup series and I love what I do here, I love the level of competition, I love the amount of time you have to focus to be successful here, but it's nice to have nights where I go away and I get in a car for a night and start at 5 o'clock and at 10:30 or 11 you're loading the car up and you're done for the day and you got to run a whole program.

"That's kind of a release for me and I take that just as serious, but it's nice to not worry about points and all those things. You just worry about winning the race on those particular nights."

Racing in the Cup series is a time-consuming business, one that involves significantly more than just the practices and on-track activity. A race weekend is a two- or three-day event filled with multiple practices, then qualifying, team meetings, and the race. Between that are media and sponsor obligations as well as fan gatherings and signing numerous autographs as one walks through the garage or hosts sessions at souvenir trailers.

Pressure builds week to week, especially for those top-flight drivers who are battling to make it into the Chase for the Sprint Cup or fighting for another championship. So slipping away to race in another series during the season or taking time in the Cup offseason to compete in other events offers drivers a fresh perspective on simply racing, a reminder of what it was like before they became championship challengers in the NASCAR ranks.

Kahne, who like Stewart owns teams in other series, says that racing in the annual Chili Bowl is always fun for him.

"It's racing that I've done in the past, so I enjoy it a lot," Kahne says. "You go and do it, you don't have to worry about a lot of things. You just race and you have fun racing. The crowd and fans come down afterward and you can spend time with them and people you don't see at the NASCAR track. So to me, it's just a lot of fun. It's really kind of relaxing and at the same time I get to do what I love and drive cars."

Richard Childress Racing's Clint Bowyer is one of several Cup drivers who cross over into the Nationwide Series week to week. At times, he says having another series in which he has a chance to run well helps him through any potential struggles. In his free time, he still likes to run around and race on a dirt track. It's familiar, comfortable and a chance to cut loose.

"Dirt racing has always been back to my comfort level and where I feel the best at," Bowyer says. "Those are my type of people, it's what I've done my whole life. When I can get back to the dirt track or back to my dirt track and work in the shop with the guys, then that's what I enjoy doing."

For some, racing in other series is an annual event. Johnson, the four-time defending Cup champion, is preparing for his third consecutive Rolex 24 with the GAINSCO/Bob Stallings Racing entry and fifth overall. Allmendinger will compete in it for the fifth time. Montoya is a past winner of the event.

As he looks at the race, he says it is still a challenge.

"It's always cool to drive something different," Montoya says. "It's funny because the first time I drove it, I just came from Formula One and I was like, 'This thing doesn't slow down, it doesn't turn, it doesn't do anything.' Now I come from this it's like, 'Oh, it's got tons of grip.' It's always a challenge ... it's very, very different."

As he prepares for the sports-car race, McMurray says that it is exciting to be a part of the same team as Montoya. But why is he adding the race to his lineup?

"I'm doing this because I want to do it, and it's fun," McMurray says. "I'm not necessarily doing this to make myself better for the Sprint Cup racing. Though I don't think it hurts to do more road races. But this is such a different type of race. It's about staying on the track and just kind of putting in consistent lap times, not necessarily the fastest lap times. Then racing with the GT cars, there is such a discrepancy in pace that you spend most of the race kind of judging how you're going to time out those passes. So it's a lot different of a race.

"Really I'm doing it just because I want to, and I think it's fun more than anything."