I have been running and will forever stay with the 27x8x12 front and 27x10 or 12x12 original design not radial, Maxxis Mud Bugs on both my current KingQuad 750 and past Sportsman 425 ATVs. I always go up to the 27" sizes to gain that little bit of extra ground clearance. You will lose some power to get them turning but if you are typically on slow going trails, you should be in low range anyway so you most likely won't notice. The Mud Bugs are one of if not the lightest, 27" tires on the market at about 21 lbs each. From what I remember, their actual inflated dimensions are more closely matched to the stock inflated dimensions. What I mean by that is say for example, these numbers are not the actual numbers this is just for example purposes, the stock tires are an inflated height (properly inflated) of 25.75" tall on the fronts, and 25.25" tall on the rears, see that inflated difference of a half an inch between front and rear? When I was on the market for tires 5 years ago, I remember the Mud Bugs out of all the tires were about identical in regards to the inflated height difference in the same places, 27.75" tall front, 27.25" tall rear. They still maintained the same inflated difference in the right places.
The reason to consider this is for proper gear ratio on the front diff. Just tossing on any set without checking into their inflated measurements might throw your gear ratio off and cause excessive wear on the front diff gears. All front diffs are geared to spin slightly faster than the rear, ATVs, AWD cars, trucks, all of them. When you mess with that ratio, depending on how drastically, bad things can happen up front.
My Sportsman 400 was purely stock, had a stock 425 engine in it at about 23 hp with no mods at all.Jjust tires and a slightly lifted front end to allow the Mud Bugs to have adequate clearance in the fender wells. In low range I was able to get that ATV to pick the front wheels off the ground going uphill if the terrain gave me the little extra bump to get them there. As a little extra thought, those Mud Bugs on the Sportsman were put on in 2003, had about 4000 kms of aggressive rocky trail time on them and were still holding up very well when I traded it in for my KingQuad in 2015. Any ATV tire that will last 12+ years of hard trail only use and keep coming back for more is a well worth it tire to consider
One other thought, ask yourself why the farming industry hasn't changed the tread design of tractor tires by much over the last century...monster trucks too, they know the design works, they've had a lifetime of proving it
