From the factory sites a comparison of the tires for the rear of the grizzly
Stock tires 24.41 high 9.4 wide weight 17lbs
ACT radials in 25 inch size 25.5 high 10.5 wide weight 24.8lbs.
The radials overall are 1.09 inches taller which will give you about 1/2 inch more ground clearance, I dont think you would need a clutch kit, the 26 inch radials are 1.79 inches taller than stock which gives me .895 inches of additional ground clearance, for my style of riding I haven't noticed a real loss of power, besides there is low range for the slow or techinical stuff, it has enough for me, but, I have noticed an increased amount of traction in the dirt. They did correct some of the speedo error that the griz has in stock form. Of course the numbers are subjective, tire inflation and rim width will make a differnce in overall height. So far I am pleased with them.
Stock tires 24.41 high 9.4 wide weight 17lbs
ACT radials in 25 inch size 25.5 high 10.5 wide weight 24.8lbs.
The radials overall are 1.09 inches taller which will give you about 1/2 inch more ground clearance, I dont think you would need a clutch kit, the 26 inch radials are 1.79 inches taller than stock which gives me .895 inches of additional ground clearance, for my style of riding I haven't noticed a real loss of power, besides there is low range for the slow or techinical stuff, it has enough for me, but, I have noticed an increased amount of traction in the dirt. They did correct some of the speedo error that the griz has in stock form. Of course the numbers are subjective, tire inflation and rim width will make a differnce in overall height. So far I am pleased with them.