Lots of negative press around the time they released their last earnings report - so a few weak hands folded and sold off their holdings in the 10's and low 11's. Obviously, in hindsight, that was a mistake because, as you said, the stock is now past 14. Part of the rise may also be because of a developing short-squeeze - there is plenty of short interest in GT. S&P has a 12-month target price of $16 on GT and given the momentum we are seeing, it is likely to climb higher in the next few weeks leading up to the earnings report on 2/11. If that report beats estimates, and if the overall market remains benign/positive, we could see GT go well past 16.
Disclaimer: long GT