FANTASTICALLY FRUSTRATING: The 2012 F1 championship winning RB8 proved to be a bit of a headache for its design team due to its unpredictability.
Red Bull team boss Christian Horner has admitted car designer Adrian Newey is "a little late" with 2013's cars.
The Briton made the admission on the Red Bull-sponsored Austrian TV channel Servus TV.
Pre-season testing for the 2013 season will begin in Spain in early February.
The fact the RB9 is running behind schedule is undoubtedly due to the fact that, while many other teams turned their attention to next year during the 2012 season, Red Bull painstakingly developed its title-winning RB8 right up until the recent Interlagos finale.
According to Newey, 2012 was the hardest season he’s ever been involved in. "In 2010 we had a fast car, maybe not totally reliable, but very good. That of 2011 was good and reliable.
"This year (2012) we sometimes had a very good car and sometimes had a reliable car, and we didn't always understand it, which initially was frustrating.
"The biggest change was the exhaust system which we had developed for two years and suddenly we had to start from scratch."