This thread has some more info:
https://www.gtplanet.net/forum/showthread.php?t=202299
hope that helps, good luck
ARCADE - Focus WRC, Daytona speedway, infinite lap race, turn around and drive at the other cars, that'll damage it. 7 Minutes and I lost both doors
dont you get a trophy for getting some part of the car falling off?
one of the hidden trophies ive heard?
Get a Ford Focus WRC, and go between one of the white markers and the wall. Keep pushing and reverse out. Your door will be missing.
I'm almost ashamed to say this, but I got multiple parts to fall off the Citroen WRC car just through my normal course of racing during one of the earlier seasonal events at Rome...