Ralf treads carefully to beat brother Michael in Montreal

He harried his brother from the start, but did not risk a pass until the Ferrari ace pitted on lap 46.

The Williams-BMW driver then smashed the lap record to build enough of an advantage to come out in the lead when it was his turn to pit on lap 50.

"I'm delighted to win this," said Ralf. "Obviously it was a great race today. The whole time I was always waiting for Michael to make a mistake but he didn't.

"I tried a couple of times at the end of the straight to get past but it didn't work," he added. "Then I decided to wait for the pitstops and hope it would work and I would take the lead there - and it did.

"I was following him quite easily today, the car was brilliant. I didn't want to risk too much with overtaking because I knew it could work in the pitstops."

"As we pulled away from the others at the start I wondered why he didn't go quicker. I knew I could get him at the end of the race and that's what happened.

"If I'd tried to get past him we both would have straight-lined the chicane or crashed and that made no sense."

He said the key to his race performance was changes in the settings overnight, plus sweltering 27 degree temperatures that favoured the Williams-BMW's Michelins.

"We changed quite a few things overnight, but the Michelin tyres worked brilliantly today. His (Michael's) tyres didn't look too good and the car looked very nervous on the track," he said

"We were hoping for a lot of sun and we got it. The hot weather was perfect. The hotter it is, the better it is for Michelin."

It was the first win by a Williams in Canada since Damon Hill's victory in 1996.

Schumacher Jr is now fourth in the championship with 22 points, two behind Rubens Barrichello, who crashed out.

Michael Schumacher increased his lead over Coulthard to 18 points as the Scot retired with a blown engine on lap 55.

For full race results, click here.