LAS VEGAS, Nev. - NASCAR's attempt to make racing better on its intermediate tracks gets its first real test Sunday at Las Vegas Motor Speedway.

The UAW-DaimlerChrysler 400 is the third race of the season, but the first in which the combination of a lower rear spoiler and softer tires is expected to have a meaningful impact.

"The performance of the tires has always fallen off at Vegas, but the new tire is falling off a little bit more, obviously," Tony Stewart said. "It's what a lot of us drivers have wanted for a long time because the fuel mileage and track position games we saw played last year have been taken out of the equation this year."

That's exactly what NASCAR had in mind when it cut three-quarters of an inch from the rear spoilers to reduce downforce, making the cars harder to drive in the corners. It also forces Goodyear to bring softer tires to the tracks.

"We're trying to get our arms around the downforce and aerodynamics of the race cars," Nextel Cup director John Darby said. "I think we're going in the right direction, if the test out here is any indication."

Stewart was one of more than 50 Nextel Cup and Busch series drivers who tested in January on 1½-mile oval.

The season-opening Daytona 500 was a restrictor-plate race, where the rear spoiler height was actually increased a half-inch from last year in an effort to curb speeds at one of NASCAR's fastest race tracks. The tire Goodyear brought to Daytona was actually a little harder than last year.

And, two weeks ago on the 1.017-mile oval at Rockingham, the tire was virtually the same compound used there last November, and the abrasive track at The Rock has always been hard on tires anyway.

It's the tracks such as Las Vegas - the 1½- and 2-mile ovals that make up more than one-third of the 36-race Cup schedule - where the changes are expected to be most noticeable.

"I think it's a great idea," Stewart said. "Now we have to budget our tires. We can't go out there and just run flat out the whole time, and with that comes a lot more passing.

"Guys who get in too big of a hurry and go out and abuse their tires early in a run will get passed by guys at the end of a run because they're more patient."

In the last few seasons, harder tires and big spoilers made the cars "aero dependent," a term describing handling characteristics cars experienced in traffic that made passing difficult.

That situation promoted strategies such as taking two tires or no tires on pit stops to gain track position, or simply trying to make your gas last longer than the other guy's to gain an advantage.

Stewart, the 2002 Cup champion, said the latest changes should make a difference.

"When it was like that a few years ago, you saw a lot more passing and the racing just seemed to be better all around," he said. "By taking some downforce away from us and giving us some softer tires, it's given us a combination that's allowed us to race."

Four-time Cup champion Jeff Gordon, a former Las Vegas winner, is also happy with the changes.

"The new tires will benefit the teams with good communication." Gordon said. "I believe we're one of those teams.

"The track grooves are beginning to open up here, so we should be able to run low or up a couple of grooves once the tires begin to fall off. The key will be communicating exactly what the car is doing to your crew."

Jimmie Johnson, one of Gordon's Hendrick Motorsports teammates, said the January test indicated that NASCAR has accomplished what it set out to do.

"I think they've reached that goal," Johnson said. "It's going to make the race in Las Vegas a lot different from what we've seen here in the past."