Saarbrucken - Thierry Neuville's lead in the world rally championship is under threat after the Belgian limped out of the German Rally on Saturday.
Neuville finished the ninth stage speed test with the rear left wheel hanging off his Hyundai i20.
After parking the car neither he nor his co-driver Nicolas Gilsoul could explain the breakdown.
"It was just a slow junction, a left turn with a cut and we don't understand what happened.
"We felt a small touch on the rear axle. We probably touched something but we don't understand right now," said Gilsoul.
Neuville's misfortune allows his rival Sebastian Ogier of France the chance to overtake him in the WRC's overall leader board this weekend.
Neuville and Ogier are tied at the top of the standings, so the Belgian's early exit gives France's Ogier the opportunity to regain the overall lead.
Ogier is the third-fastest overall, 29.9sec behind German rally leader Ott Tanak after the 12th super stage of 21, with Norway's Andreas Mikkelsen second at 23.0 back.