Rusty Wallace is the leader among active drivers at Martinsville (Va.) Speedway with seven career victories, and even he's unsure how the track's new surface will respond to racing today.

The surface has been commended by drivers this week for being smooth and fast, but questions remain about whether it will feature two grooves for racing when the Subway 500 in the Nextel Cup Series is run.

"I think there are a lot of unknowns right now," Wallace said.

The new surface, with concrete in the corners and asphalt in the straightaways, was put down this summer, after part of the concrete came loose in the spring Nextel Cup race, possibly costing Jeff Gordon a victory.

New tracks typically present problems immediately after they are installed, largely because they haven't been raced on. Over time, small bits of rubber that come off tires will fill nooks and crannies in the surface, easing its grip on tires and allowing for more consistent racing.

Many drivers were most interested to see how the track responded during a practice yesterday, and Jeff Green, for one, emerged still pessimistic.

"Everybody is running about the same speed and if you get off the bottom, it seems like there's so much stuff on the outside it takes a lap to get your tires cleaned off," the Petty Enterprises driver said.

"It's going to be tough to pass, I think."

Changes, and questions, are among the last things Gordon wanted to have to deal with at a track where he has dominated in recent years, winning three poles and two races in the series' last three visits.

Gordon, a four-time champion, is third in points, 74 behind Kurt Busch and 50 behind Dale Earnhardt Jr. halfway through NASCAR's 10-race playoff.

The leader knows the championship is still up for grabs.

"I believe a playoff system is an elimination-type series where you have one bad game and that puts you behind, but you can come back from that," Busch said. "You could be down 3-0 and make it back."

* FORMULA ONE: The hometown favorite won the pole position at the Brazilian Grand Prix in Sao Paulo after the seven-time world champion crashed during practice.

Rubens Barrichello completed a lap around the 2.678-mile Interlagos circuit in 1 minute 10.646 seconds, 0.204 of a second ahead of Juan Pablo Montoya, for his 13th career pole and fourth this season.

Michael Schumacher, the seven-time world champion and Barrichello's Ferrari teammate, had the eighth-best time at 1:11.386, but will start 18th because of a 10-place penalty for changing engines after crashing.

Minutes before the end of the final practice session Schumacher spun on a turn, slid off the track and struck a tire barrier with the back of his car.

"Very simply, I lost the car," he said. "I couldn't control it anymore. I went into over-steer. That's why I went off."

* TRUCKS: In Martinsville, Va., Jamie McMurray held off Dennis Setzer on a restart with 12 laps to go and completed a career hat trick. The Nextel Cup driver, making only his third start in a truck this season, became just the eighth driver in NASCAR history to win in the premier series, the Busch Grand National series and in a truck.

* BUSCH SERIES: Martin Truex Jr. extended his points lead in Memphis, holding off Greg Biffle in a green-white-checker finish in the Sam's Town 'He Dared to Rock' 250.

Truex's victory, his sixth of the season, extended his lead over Kyle Busch to 208 points.