Glenn I recommend a 27x9x12 on all four. That is what we have done on a few 900 Trails and highly recommend it. On the 800 50″ RZR we use 26x9x12’s. 11″ wide on the rear is a wide tire and will put you well past the 50″ restriction. It should work fine a believe as far as fitting on the machine, however if you have trails/trail heads with restricted 50″ gates/posts to got through like we do. 11″ rears will rub and possibly be to tight to fit through the restricted openings. Even 10″ rears on the 900 trail cause some issues fitting through the restricted trail head posts/openings. A good 27x9x12 all the way around on all four wheels look great, great stance, great handling and do not stick out. You still CANNOT rotate from front to back since the wheel offsets are different from the rear and front. For our spare wheel and tire setup I went with is a stock “rear” offset and it works great if you need to run it on the front to get you out if you have a flat. The stock “front” wheel offset does not work if trying to put it on the rear.