i don't think the two diferent size tires will matter much . there are way to many 4x4's mudding to prove it wrong. i would go with the same size front and rear. the onlt problems people have ever had with tires is when they go with something to aggressive and they have a heavy thumb they snap axles . i ran 589's on my hpx and they was a great tire lasted forever and can't recomend them enough if your in the mud.i now run outlaws on my rhino and they are some really great tires only bad thing is their rubber is really soft and they will wear down fast if you run on the road not to mention they ride pretty rough at low speeds but after to pick up a bit os speed they level off. if i had to go with a tire on a four wheeler i would go with some 589's and nuthing over 26" the 26" has the same deep lugs as the 27"28" .the 25's have a shallow lug and well they just don't cut it when it comes to digging into the mud and biting . i'm not saying they won't do the job but i always went with the deepest lug i could find and a lig that has lots of space in between them for easy cleanout when in the mud.bighorna and bearclaws are nice tires but if you get into some mud with them they just cake up and you have to spin the you know what out of them to get the mud to sling off them not so with the 589's the lugs are far enough away that the mud with fall off in chunks at low speed. another problem with the 589's and outlaws are when you come out a mud hole you don't wanna step on the throttle at first go slow for a foot or two to let any mud chunks that are left fall off other wis you'll be bombarded by softball size chunks of mud flying all over. over all i would say get the 589's that is unless you ride in the thick stuff then get you some outlaws.
