So I need to swap out the shitty ITP tires on the XP I picked up. I am strongly looking at the 28x10x14 / 28x10x15 GBC Mongrels. I primarily ride desert like Ocotillo and do quite a bit of Jeep style trails. I want the 28's for clearance. How badly will I lose the bottom end with these without doing clutch work on the XP? The other tire I am looking at is the OG 27x9x12 Bighorn (which I know is close to a 28" but still a lighter package)