"We made a decision to go for much smaller (brake) ducts to try and get some more aerodynamic performance out of the car and really it was wrong," said chief operations engineer Sam Michael.

"Every circuit is hard on brakes anyway these days because you are always pushing everything as far as you can but here we just stepped over the limit obviously."

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Colombian Montoya had raised the BMW-powered team's hopes in qualifying with their first front row start of the season but he was slow off the line and was down to fourth at the end of the first lap.

He then retired 20 laps from the end.

"I knew this race would be difficult," he said. "It's been like this every year so we know this track is hard on the car."

"I started having brake problems in the very first part of the race, with the pedal going very long, but they then seemed to come back after the first pitstop."

"I am not frustrated. I've had this before and it's not worth getting annoyed about."

Ralf Schumacher, younger brother of Ferrari's six-times world champion Michael, finished sixth after conserving his brakes to the finish.

"I don't want to call it the team's fault," said Ralf. "The team does its best to give us the best possible cars and I don't call it a mistake, it was just pushing it very far, a bit over the limit."

"But it was possible to finish the race."

Williams slipped to fourth in the championship, two points behind BAR and 12 adrift of Renault.