Nigel Mansell, the defending IndyCar champion, was the fastest qualifier for the Michigan 500 race yesterday with a speed of 233.738mph. It is the third time he has managed pole position this season. Raul Boesel was second, with Michael Andretti completing the front row of the grid. In trials, both Mansell and Andretti had speeded to 235mph and the first five qualifiers for the race managed to exceed 230mph for the first time in IndyCar history. The hot weather, which encouraged sliding, slowed down times for the qualifying session proper, however. 'This is one of the most challenging circuits in the world,' Mansell said. 'To go more than 230 mph is quite something. It's a bit of a survival race. It's a punishing circuit and you have nearly constant speeds of 226 mph.' Al Unser Jnr, who is leading the IndyCar Championship is 14th in the grid.