If there is one thing Iron Man Director Jon Favreau could complain about, it is that the Audi R8 and Q7 used in the movie are too well designed making the stunt scenes a logistical nightmare.
The first stunt scene (in the video above) features a family skidding to a halt in their Audi Q7 which proved a major problem due to the anti-lock braking system, even after the wheels were sprayed with WD40 and the ground was splattered with water, it still wouldn't work. In the end they spent 2 hours under the hood with all their tools and blow torches to turn off the anti-lock brakes. Unfortunately this isn't where the problems stopped, following the skid the Q7 is held in the air by Iron Man when the cars wheels should be spinning round but this time the traction control was in the way.
In the final scene of the movie, the Audi R8 should crash into Iron Monger's (the Bad one) leg and flip over, but obviously the set directors failed to realise the sport cars low center of gravity as each time the car would just spin to the side. Check out the video below to see the full behind the scene details, although be warned there will be a lot of wrecked R8s which could prove difficult for some people to see.