You know you're old when?

When you go out to interview a driver and are shocked by how young he looks when you're sure you interviewed him in the 1980s.

Tommy Milner laughed.

"You're thinking of my father," said the American Le Mans Series points leader in the GT class. "He used to race at Summit Point. Is that where you remember him from?"

Yes, I remembered his father from Summit Point.

This Tommy Milner is 26. He and his teammate, co-driver Oliver Gavin, lead the GT championship in their No. 4 Corvette C6.R by 18 points over Corvette teammates Jan Magnussen and Antonio Garcia in the No. 3 companion car coming into Saturday's ALMS race at the Baltimore Grand Prix.

"I grew up around racing," the younger Milner said. "At four months old I was at the racetrack. ... My dad got me a go-kart when I was 14 or 15, but I don't think he wanted me to be in racing.

"My dad says he hates all racecar drivers -- just some less than others."

His father still gives him advice, but by this time, the son knows nearly as much as his dad.

Up to this year, Tommy Milner's best year was 2010, when he finished third in a BMW. Now, he has a shot at a championship.

"We took a huge step with our car this year," Milner said. "We definitely have a chance to win every race. The situation is new for me, but my co-driver, Oliver Gavin, has been in racing a long time. He's a fantastic driver."

Milner and Bryan Sellers, who drove a Porsche 911 GT3 RSR to his second career win in the American Le Mans Series Sports Car Challenge GT class last year with his teammate Wolf Henzler, were in town this week demonstrating the difficulties and importance of a driver change during a race.

"There is no strategy in a two-hour race," said Milner. "It's basically one pit stop, and whoever is the fastest and can make the best of their qualifying position is going to come out on top. Any mistake and you're done because there's not much time to come back."

Thus the importance of the single pit stop. Blow that and you could be out of hope.

Sellers, whose team will be an underdog Saturday, explained the entire pit stop has to be done in 45 seconds.

"The driver change is really very important," Sellers said. "The quicker we do our change, the longer we have to do everything else. The stop usually takes about the time it takes to run half a lap here. If you have to stop under the green flag, it can be the difference in leading a lap or being down a lap."

Sellers said it never goes as smoothly as you think it will, but he and his partner, who have been together now for three years, have established a routine.

"We can do it in about 10 seconds, which is incredibly fast," he said.

Everything went well for Sellers and Henzler here last year, and they're hoping for a similar performance this time, that could bring them their first win of the season.

"To win in the ALMS, everything has to be perfect," Sellers said.

Things were not so perfect for Milner and Gavin a year ago in opposite team cars, problems relegated both of them to also ran status.

As teammates this season, everything has changed for the better. And the team practices pit stops 20 to 30 times every weekend, to make sure everything goes well in the race.

But the driver change in the corvette takes a little longer -- about 18 seconds, Milner said, because of a side impact protection box outside the roll cage that slows movement in to and out of the car.

But the overall time in the pits is a little less, about 40 seconds for a full stop.

"You hope it can be done under yellow [caution]," Milner said. "We have to fight so hard for just a tenth of a second on the track. If you lose even one second in the pits, it's hard to make that back up. Losing a second is a major handicap."

Milner and Gavin have three wins this season.

"Prior to this year, I had zero," Milner said. "This year has been particularly good to me. When I won the first one at Long Beach in the second race of the season, Dad was the first person to call. He's now calling me his retirement plan."

Milner laughed. It's pretty clear his father has found a driver he likes.