LONDON, England - Red Bull is investigating whether a fault in Sebastian Vettel's chassis is causing the reigning champion's 2014 trough.Team boss Christian Horner says the reigning quadruple World champion is lacking the "feel" for the RB10, named Suzie, while others think the German is simply being outclassed by his new team mate Daniel Ricciardo.Helmut Marko, a champion of Vettel's career since his boyhood, has some other theories: "When downshifting, Sebastian needs a stable rear for his special style of driving. With all the new systems, he doesn't have that yet."BRAND-NEW 'SUZIE'Marko tipped Vettel to get it right - eventually. "In 2012 it was the same and by the time he was happy with the rear he was unbeatable," Marko was quoted as saying by Germany's Sport Bild. But there could be more to the story...Marko said, referring to the 2014 Chinese GP: "We don't understand why Vettel's tyre wear was so much higher than Ricciardo's but we're investigating whether his chassis has a fault."Marko said Red Bull's target was to eliminate any chassis flaw as the potential origin of the problem by giving the 26-year-old a brand new 'Suzie'. "When she's ready, Vettel will get it."However, Marko added that if a chassis flaw was not the problem then he could not guarantee a quick fix to Vettel's troubles. "2014 is so complex that even the engineers don't understand everything," he explained. "That makes it even harder for Seb to tune the car to his needs."But Sebastian is a perfectionist. He'll tinker with it until he gets it right."Stay with Wheels24 for the 2014 F1 season – fresh reports every day.