Your speedometer and odometer will both be wrong with different sized tires. If you had 26" tires and switched to 27" you need to add approximately 4% to get the true speed and mileage. If you switch from 25" to 27" add 8 percent.

 

Hey fellas I just bought an 08 800 sportsman was just wonderin about servicing the diffs, Not quite sure what gear oil to run in em if it just 80/90 or a specific type I need? Anyone out there could a guy out lol ?