I was under the impression that Bighorn run true to size. And when compared to say an ITP tire of the same size it's usually taller. A guy over at highlifter just bought 25" Bighorns and put them on his Vinson. He has a picture of his Vinson with the 25" tires next to another Vinson with the stock 25" tires and the Bighorns as smaller. I don't get. Here's the links with his pics.
http://img.photobucket.com/albums/v635/Irish317/ATV4.jpg
http://img.photobucket.com/albums/v635/Irish317/c6aad412.jpg
http://img.photobucket.com/albums/v635/Irish317/ATV5.jpg
http://img.photobucket.com/albums/v635/Irish317/5427c8e4.jpg
http://img.photobucket.com/albums/v635/Irish317/ab5a4e09.jpg
http://img.photobucket.com/albums/v635/Irish317/ATV4.jpg
http://img.photobucket.com/albums/v635/Irish317/c6aad412.jpg
http://img.photobucket.com/albums/v635/Irish317/ATV5.jpg
http://img.photobucket.com/albums/v635/Irish317/5427c8e4.jpg
http://img.photobucket.com/albums/v635/Irish317/ab5a4e09.jpg