I installed 26 inch Terracross tires on my 2003 Grizzly. I noises a bad virbartion when I run about 30mph hard top road is that normal? someone said I needed to balance these tires.

 

I can't say I've heard about balancing ATV tires(maybe it's new to me) but you shouldn't have to balance them. How are your front bearings? slight play in them can cause vibrations, as well as a worn CV joint. Have you checked everything over? Loose nuts/bolts can also cause this.