Motorsport: Mechanical withdrawal threatens Kiwi Scott Dixon's IndyCar title defence

Kiwi champion Scott Dixon has been forced to withdraw from the latest IndyCar round at Madison, Illinois - a major blow to his quest for a sixth title.

Starting eighth on the grid, Dixon's car suffered a holed radiator on the opening lap and lost water pressure, before eventually pitting lap 65. He official retired from the race with 48 of the 248 laps remaining for the leaders.

"I'm really bummed for the team," he told ESPN afterwards. "The car was actually really good, especially in the latter part of the stint.

"We really came on and another lap or two, we would've passed Pagenaud. We had a good start and the car felt strong, I just feel bad for the whole team."

Dixon entered the event trailling American championship leader Josef Newgarden by 52 points, but just 17 astray of second-placed American Alexander Rossi and 12 behind Frenchman Simon Pagenaud.

Luckily, none of those ahead of him took full advantage of Dixon's misfortune in a race won by Japanese Takuma Sato. Pagenaud finished fifth, Newgarden seventh and Rossi 13th, a full lap behind the winner.

But Dixon lost ground and remained in fourth overall, now 70 points behind Newgarden, with only two races remaining.

"We've got to really go for wins here," he said. "We've been saying that all along and we've had some pretty good runs.

"We have to put our heads down. Had we been able to show the full potential of the car, we would have looked good tonight, but it just wasn't meant to be."

Dixon had closed the margin on the series leaders over the past two months, with four straight podium finishes and victory at Mid-Ohio in July.

Next weekend, the competition races in Portland, Oregon, where Dixon finished fifth last year.