Indianapolis ? The weather changed Helio Castroneves’ plan Thursday in practice for the Indianapolis 500, but it didn’t slow him down.

Rain shortened the scheduled seven-hour session at Indianapolis Motor Speedway to just under four, with more of the wet weather in the forecast for today — the last full day of practice before pole qualifying.

“Because of the weather, today we tried to play a little bit like it was Friday,” said Castroneves, a two-time Indy winner. “We don’t know what the weather will be like Friday, so we tried a little stuff that we were supposed to test tomorrow.”

Whatever it was his team tried, it appeared to work well when Castroneves topped the day’s speed chart with a lap of 221.156 mph. It was the best lap for his Toyota-powered Dallara since practice opened Sunday. The race is May 30.

With the sometimes-heavy rain washing away a lot of the tire rubber accumulated on the track earlier in the week, speeds slowed a bit Thursday for most of the drivers.

But things picked up during the final hour of the day, with cool temperatures, light winds and overcast skies making conditions nearly perfect for speed.

The fast lap by Castroneves came with about 20 minutes left in the session and just moments after Rahal Letterman Racing’s Roger Yasukawa posted a 221.093 and two-time IRL champion Sam Hornish, Castroneves’ Team Penske teammate, hit 220.956 in his fastest lap of the week.

“The good news is that I’m happy with the car,” Hornish said. “Having said that, Pole Day often throws a curve ball with respect to track and weather conditions. So, hopefully, we’ll get a chance to run tomorrow.”

Yasukawa also was happy.

“The track picked up grip at the end of the day,” he said. “I think the track will get faster as the rubber gets built back up on the track.”

Brazilian driver Helio Castroneves prepares to practice at Indianapolis Motor Speedway. Castroneves had the fastest lap Thursday in Indianapolis.

Castroneves was also fastest on Monday after running second Sunday to IRL champion Scott Dixon.

“Unfortunately, I did have a tow,” Castroneves said of his fast lap. “Each time I went out, somebody came out of the pits in front of me and I couldn’t get a lap by myself. But I thought, ‘Just be happy you’re on top of the list.’

“And there was a significant improvement in my car. We were pretty close to the same time today. So, even if I did get a tow, with these weather and track conditions, that’s still an improvement.”

The practice ended abruptly about five minutes early when Scott Sharp spun and slammed into the energy-absorbing SAFER barrier in turn one. His car sustained heavy damage, but Sharp, a former Indy polesitter, was not injured.

Buddy Rice was fourth fastest Thursday at 220.778, followed by Tony Kanaan at 220.733, Vitor Meira at 220.666 and rookie Kosuke Matsuura at 220.646.

Kanaan, who drives for Andretti Green Racing, remains the fastest this week with a lap Wednesday at 222.668.