DOVER, Del. -

Even the top stock-car racers in the world won't drive 160 mph in the rain.

So while Wednesday's intermittent showers did not deter the usual crowd of white-haired retirees from taking their favorite spots at the slot machines and blackjack tables in the adjacent casino, Goodyear technicians gazed up at the skies over Dover International Speedway and decided to halt their 2-day tire test more than 4 hours early.

Kurt Busch, Ryan Newman, Martin Truex Jr. and Kevin Harvick had all parked their cars and cleared out of the state capital by noon, leaving only A.J. Allmendinger and Marcos Ambrose to spend a sliver of their lunch break with the media.

And even after the pair returned to the makeshift garage area at the south end of the oval, only Ambrose made it back onto the track in his putty-colored No. 9 Ford for a couple of top-speed laps before the test was stopped for good at 12:30 p.m.

So what was learned?

No one will know for sure until NASCAR returns to Dover in 6 weeks for the June 3 Sprint Cup race benefiting Autism Speaks, the FedEx 400.

Based on the data collected over the day-and-a-half test, Goodyear will develop a new tire to tame the Monster Mile's concrete track. The challenge is to find the right compounds that will properly "rubber in" the racing surface without causing marbles - or chunks of tread - to build up in the high-banked corners.

Ambrose completed about 100 laps Wednesday morning and learned something the Goodyear engineers will have to take into account. "The tire was so fast that it would turn this into a one-groove racetrack," the Aussie said with a smile. "We'd be playing follow-the-leader."

Allmendinger, in his first season with Penske Racing, welcomed the extra seat time in his No. 22 Dodge.

"In this sport, you're always learning," Allmendinger said.