^ I know, that's my intuitive answer ... front, but I've read many articles that says the better tires should be placed in the rear.
Tire Rack Tech Info -
https://www.tirerack.com/tires/tiret....jsp?techid=52
Intuition suggests that since the front tires wore out first and because there is still about half of the tread remaining on the rear tires, the new tires should be installed on the front axle. This will provide more wet and wintry traction; and by the time the front tires have worn out for the second time, the rear tires will be worn out, too. However, in this case, intuition isn't right...and following it can be downright dangerous.
When tires are replaced in pairs in situations like these, the new tires should always be installed on the rear axle and the partially worn tires moved to the front. New tires on the rear axle help the driver more easily maintain control on wet roads since deeper treaded tires are better at resisting hydroplaning.