will 12″ wide tires fit stock rear rims

I have a 2015 Rzr 900 trail and just purchased 27" bighorns. The fronts are only 9" wide so I know they fit but the rear are 12" wide so I’m not sure. Will they fit on stock rear rims? Think stock rims are maybe 7" wide. Any other issues I’ll need to address either? Help me out if you can. Thanks guys!