Autodromo Hermanos Rodriguez sits more than 7,000 feet above sea level. Credit: Donald Miralle/Getty Images

Notes: Mexico altitude takes some by surprise

MEXICO CITY -- The obstacles are numerous for this weekend's Telcel Motorola 200 Busch Series race.

The Busch Series is racing outside the United States for the first time, is racing on the 2.52-mile Autodromo Hermanos Rodriguez track for the first time -- and the first time on a road course, period, in four years.

As if that weren't enough -- and it has been through the first two wreck-filled practice sessions -- drivers and teams have to deal with an unseen complication: Mexico City sits 7,380 feet above sea level.

Jamie McMurray crashed in the morning practice session in Mexico City Credit: Donald Miralle/Getty Images

Big deal? Well, yes it is. Higher altitudes mean thinner air and less oxygen. And that could lead to breathing problems - both for humans and racecars.

How high are we talking about? Well, Denver likes to call itself the "Mile High City," but Mexico City is more than 2,000 feet higher.

"I didn't realize it when I got here, but I think you'll see a lot of fatigue happen on Sunday," Jamie McMurray said. "You don't realize how hot it is. You don't sweat, but you get tired, you run out of air.

"I've run to the bathroom twice, and you can feel it. You're like, 'Wow.' This is the highest I've ever been -- no pun intended."

David Stremme compared running here to running at Pikes Peak, which has an altitude of a little more than 4,000 feet.

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"When I first got here yesterday, it was a little hard to breathe, but now I'm fine," Stremme said. "Our teams travel all over the county. I mean, we go to California, and the air's hard to breathe there because it's so nasty. You just get used to it."

But the Mexico City altitude affects more than the drivers. Robby Gordon said the thin air reduces downforce on the cars.

"It's just like landing in our plane yesterday when we had to come in 15 knots hotter than we normally come in just because we're landing at 8,000 feet," Gordon said. "The cars obviously lose power. Dehydration is going to be a really important thing. They talked about that to us in the drivers meeting earlier. You've just got to keep it all in perspective."

Gordon, though, has a simple solution to the lost downforce.

"If the car won't hold, slow down," Gordon said. "You have to do what your car can do."

Kevin Harvick said his engine has felt "spongy" because of the altitude. Less air can be forced into the engine, robbing it of power.

Rain tires, rain tires go away

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Goodyear brought rain tires to the track this weekend, and the forecast originally called for a 30 percent chance of precipitation. But that has since been downgraded to 10 percent, so the grooved tires likely won't be used.

But they're here if needed. Busch Series director Joe Balash said NASCAR would make the determination on what tires to use, and if it rains during the race, the sanctioning body would stop the race and let teams change tires.

"We're not going to do it random," Balash said. "We're going to stop the whole field, let 'em come in and pit to make sure their wipers are working and their marker lights are working and then put them back on the racetrack."

Wiring for the light is already in place, and the wiper motor is mounted. The wiper blade would be installed if NASCAR makes the call to switch to rain tires.

"We're on a road course in an international marketplace," Balash said. "We've got a great crowd that's going to be here, and they want to see our product. We want to be able to put on the show they deserve."

Jamie McScary?

A large contingent of Mexican media is here, of course, but thus far they've avoided McMurray.

"I keep getting my picture taken, but I think they're all scared to talk to me," McMurray said.

Check that expense report

Carl Edwards had never driven a stock car on a road course before this weekend, so he sought the advice of veteran road racer Boris Said.

"He helped me a lot on how to drive one of these stock cars on a road course and how to use the brake and how to let it coast into the corners - good standard procedures to use every lap," Edwards said.

Most of Edwards' questions were answered over dinner Thursday night.

"I wore him out last night at dinner," Edwards said. "Jack (Roush) doesn't know it, but he bought Boris dinner. It was cool. I bet he won't talk to me tonight, though."

Fellows familiar, sort of, with track

Ron Fellows Credit: Autostock

Ron Fellows is one of the few drivers on the entry list who has experience in a full-bodied car at Autodromo Hermanos Rodriguez. Fellows finished second to Scott Sharp in an SCCA Trans-Am race here in 1991.

"It was very different," Fellows said. "It was a different surface. This last corner was quite a bit more wide open. And as you go down under that Camino Real Bridge you'd go left and then right and another right into another series of esses. So it's a bit of a shortcut.

"The track is a lot of fun. But it's frustrating when you know what you want the car to do and you can't get it to do it. It's so easy to lose time. The chassis set-up is going to be super critical."

Fellows was fast in both practices and should be among the leaders Sunday. He's won three Busch Series races, all at Watkins Glen.

"The corners are fast -- particularly the very last corner here," Fellows said. But there's not much grip. And that's the problem. I almost got myself into trouble a few times because the radius of the corner increases. You're in there and you feel pretty good and then all of a sudden it starts to push and then as soon as it does that then the back goes. So there's not a lot of grip. And then with all the turns in the back, we're just trying to get as much lateral bite as possible."