A flat tire caused Jimmie Johnson to wreck Wednesday during an important test at Lowe's Motor Speedway, sending Goodyear officials searching to find the right rubber to use on the freshly paved surface.

Johnson had completed about 20 laps when he felt his right rear tire rapidly losing air. He couldn't finish the lap before the tire went flat, sending Johnson into the wall of the fourth turn.

"We're still looking at the tire and trying to find a concrete determination as to why the tire went down," said Rick Heinrich, product manager for Goodyear. "We don't know if it was a puncture or wear-related at this point."

Johnson, who has won four in a row and five of the past six races at Lowe's, left the track because his car was damaged beyond repair. He was not injured.

"I'm not quite sure what caused it," Johnson said in a statement. "I know they are looking at it, and I'm sure they'll figure out what happened. There wasn't much else we could do, so we packed up and went home. For the time I was out there, the track still felt like Lowe's Motor Speedway. It just seemed much, much smoother than it's ever been."

His accident was the only major incident during the two-day Goodyear test that will determine which tire should be used for the track's two big races in late May. Lowe's officials spent $3 million this winter to repave the surface, which was too slick last season after it underwent two grinding projects to smooth the bumps.

Both of the track's premiere races were caution-plagued last season -- 37 total -- and the October race was a particular mess because of numerous tire failures.

It could take weeks for Goodyear to decide which tire will be best because the track surface will continue to change as more and more cars drive on it.

Bobby Labonte, Kevin Harvick, Scott Riggs and Johnson were the only drivers in this test. Goodyear could choose to hold another test, and the track will be open to all Cup teams in early May for practice on the new surface. That activity, plus action from various driving schools, should lay enough rubber on the track to change the conditions considerably before the May 20 all-star race.

The only thing certain is that the speeds should reach records. Labonte said his laps Wednesday were a tick off of Elliott Sadler's track record of 193.216 mph.

Sadler's mark was set in qualifying, when a car is designed to go as fast as possible for only one lap. The times posted during the test were in race trim, when a car is supposed to be much slower.

"It would not surprise me if you saw a 197-mph lap," track president Humpy Wheeler said.

Increased speeds is the danger on any repaved track. When Lowe's was resurfaced in 1994, the qualifying record jumped from 177.352 to 181.439. So Goodyear and NASCAR will work to find a proper way to control the speeds.

Although using horsepower-sapping restrictor plates is an option, no one really wants to use them.

"It's going to be fast, but fast enough that we need restrictor plates? Absolutely not," Riggs said. "That would be a horrible decision. We always set a new track record every time we go to a new surface. We expect the speeds to be faster. That's just how it is."

DARLINGTON TICKETS SELLING: Fewer than 8,000 seats remain for the Dodge Charger 500, and the strong sales have Darlington Raceway leaders thinking of expanding faster than they had imagined.

Track president Chris Browning said he expects tickets for the Nextel Cup event to be gone in two weeks and that construction on a 6,300-seat grandstand in Turn 1 should be complete by next week, more than a month ahead of the May 13 Dodge Charger 500. The additional seats push the capacity at NASCAR's oldest superspeedway to about 63,000.

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