YES you will need new wheels, as the 11 inch wheels you have now, will NOT hold a 12 inch diameter tire
and also, you DO know your going to notice a bunch of power loss going from a 24 inch tall tire to a 27 inch tall tire that is also heavier as well as taller and slightly wider!!
and keep in mind this is a 4x4 atv, which means you need to have the same height (tall) tire on BOTH front of atv as well as back, as if not, you can damage your drive train!
and also, you DO know your going to notice a bunch of power loss going from a 24 inch tall tire to a 27 inch tall tire that is also heavier as well as taller and slightly wider!!
and keep in mind this is a 4x4 atv, which means you need to have the same height (tall) tire on BOTH front of atv as well as back, as if not, you can damage your drive train!