This is the thread by BarRZR on RZRforums.net and is where I got my figures. I think the 700 is running 36hp? That is the number I used in the formula in the thread below.
Think of the tire the same way as a sprocket or a gear, the circumference of which will, obviously, travel further per revolution with a relatively bigger tire than a smaller. So, extending that analogy, by mounting a larger-diameter tire, you are effectively "raising" the gear-ratio. "The difference in travel can be calculated by applying the circumference formula: C=pi X D, where pi=3.1416 and D=diameter. Now, the loss in power with this new "gear-ratio" can be, to a first-order approximation, calculated by dividing the circumference of the smaller tire by the circumference of the larger tire, which will produce a decimal fraction. This decimal fraction multiplied by the gross power that you had before the tire-change will (again, to a first order) be a good approximation of how much power remains after the increase in tire diameter.
I found somewhere there was a formula for weight also but cannot find it again. I think I agree with the above statement that I am not going over a 26 on mine. I don't try to climb Everest but do haul 4 guys with and a deer hanging off the back rack through the bottoms in Louisiana so do need to keep my power up as much as possible. When I can afford it I will put new shocks on. I need those. I would love portals but that ain't gonna happen at those prices and I know a guy. It will even be a while before I can afford new shocks and tires much less portals.