And then when guys by replacements they do the same thing? Why is this?
Thanks.

 

It's because the skinny tires make it easier to steer. Fat tires on the front would make for very hard steering.

 

to quote kurt angle "its true. its true."

 

As well as helping your ATV steer easier, it will even out the drivetrain load on a 4x4. Think about it, if the front tires were the same width as the rear, they would have to push all the mud, making the front end do most of the work, plus making it harder to steer (because of the increased load). If the fronts are narrower, they push some mud (or snow) out of the way in their quest to find traction, and the rear push it a little farther, and the loads are equalized better. Also, the rear wheels are usually carrying more weight. For pure mud-bogging, it might be better for the tires to be equal in width, but for 99% of driving, you are better off with narrower ones up front.