CHARLOTTE, N.C. -- It is race week here in Charlotte, so we asked this question: Who knows way more about your favorite NASCAR Driver than the driver's own family? Just ask Tony Stewart.

Tony Stewart, Greg Zippadelli

If you divide Stewart’s car number, 20, in half, you get an equally important number in his successful career.

“This is our 10th year together,” Stewart says of Crew Chief Greg Zippadelli. “It’s the longest current driver/crew chief combination of NASCAR.”

How has this partnership lasted this long? Zippadelli says like a good car, when it works it just works.

On working with Stewart, he told me, “I think we can be very honest with each other. We don’t let our friendship get in the way of our professional.”

To which Stewart responds, “We’ve got the same passion and desire to win races and our attitudes and our tempers are a lot alike. I mean, I show mine a lot more than he does his.”

And that leads to another part of Zippy’s job, one that he doesn’t mind joking about.

As racing fans know, Tony Stewart will “speak out” from time to time. And his crew chief often tells him when to rein it in.

To that, Zippadelli responds with a smile, “I don’t find it anywhere in my contract, but I guess it is part of my responsibilities.”

When it comes to the track, fans know these guys are serious. But their relationship goes way beyond the car and the shop.

Stewart speaks fondly of his right hand man, saying, “We are so much alike and we both care about each others' family, and when you spend 120 days a year with somebody, you got to feel like you are part of their family.”

Stewart and Zippy, as he calls him, are going to feel even more like family soon. Both are building vacation homes in a new development in the hills of southwest Virginia. That could be a place, I learned, for Stewart to “drive” his newest obsession.

During our talk, Stewart revealed this. “I just got a horse about three months ago, and I just yesterday figured out how to get it out of park and get into first gear and get it walking,” Stewart jokes.

He’ll apparently have an audience in Zippadelli’s two kids. Zippy says, “I’m sure Zack and Ellie will want to go down and watch Uncle Smoke get thrown off the horse.”

When talking about each other, these two are full of humor. But before long, as you’d expect, the conversation always comes back to the serious business of racing.

In closing, Zippadelli sums it up, saying, “We’ve had some good days and we’ve had some really bad days… and that is what we focus on.”