Off it, they have a relationship held together by Play-Doh.
The leaders in the Chase for the Sprint Cup, Johnson and Kenseth take a different approach when they're behind the wheel, hanging out together and with each other's families.
Their daughters are so close that when Johnson took his daughter, Evie, to a local store in Martinsville just to get out of the bus, her first instinct was to get a gift for Kenseth's children.
"She had been in there for so many days, and my daughter wanted to buy Play-Doh for Matt's kids," Johnson said.
It didn't stop there.
The next day, Johnson and Evie brought the Play-Doh to Kenseth's hauler and Katie Kenseth, Matt's wife, invited Evie to stay and play for a little while. Thinking nothing of it, Johnson said sure and headed back to his hauler.
Only when he got back did he realize what he had done.
"When I went back to my bus, my wife was like: 'You let her stay there? It's race day, you can't do that to Katie,'" he said. "I said, 'I know.' I knew I was going to get in trouble for this, but Katie insisted. She was like, 'You go get her,' so I went back down to get her."
The friendly relationship isn't too much of a surprise.
As the drivers of this generation have had children, the bond among them has grown. Once a place to go for solitude, the motorhome park at NASCAR races has become more like a playground, and it has carried over into the garage.
"Seven or eight years ago, the motorhome park was always quiet and everybody went in the bus, locked their doors and nobody would talk to each other and do nothing," Kenseth said. "Now, with all the kids, it's a lot of fun because we actually get to probably be more friends than we've ever been before in the garage area and motorhome park because our kids are playing together and kind of brings everybody together. That part is always fun and relaxing."
It's led to a different feeling for Johnson than the last time he was in the hunt for the Chase championship in 2010. Back then, he was battling Denny Hamlin for the title and the relationship wasn't quite the same as he has with Kenseth.
"I didn't want to talk to Denny," Johnsons said. "When I saw him, I wanted to look the other way. Matt and I are both on stage, we have our daughters and they're talking, we're chatting. It's just much more relaxed in that respect."