Well I can't really tell you on the performance difference between the factory 25" rubber and the 27" that I have because I had the 27's put on before I ever picked up my RZR. I have had my speedo up to 58 mph which is calibrated stock for 25" rubber so I can only guestimate that I must be doing over 60 mph if you consider the tire size. I should clock it with my GPS to get a better idea on the actual speed.  All that being said it has alot of jam out of the hole and I'm expecting that once I install my DFR clutch kit it will be even better. 

Some people say that removing the spacer will reduce low end torque and mid range power, but it really doesn't make sense if you look at the mechanics of the clutch. AS far as I can figure the only proven side effect is you go faster.

Got the RZR with the 27" tires on bruiser rims and have put about 150 km it and so far no issues with rubbing or clearance at all. The Mud lite XTR's have so far proven to have excellnt traction and a great ride. Looks aren't too bad either. All though I haven't really put the RZR through it's paces yet I am quite happy with the set up so far. I'll hopefully post up some pictures soon if I can mange to get some.

Just curious to see if any one out there is running 27" rubber on their RZR and what kind of mods they had to do to get them to fit. I'm looking into running a 27x10" R14 up front and a 27x12" R14 out back on mine and was hoping I could get a little feed back about tire rub and clearance issues.