I found a speed calculator for atv's. It allows you to put in the gear ratios, engine, max rpm, sprocket sizes, and tire size then calculates speed for every gear. I'm running 14 front, 42 rear with 18" tires and it says it will do 57.4mph in 6th gear at 6,676rpm. I need new tires kinda bad. the front's are dry rotted and the rears are bald. I'm planning on putting 20" tires on the rear and 21's on the front. May also put a 13 tooth sprocket on the front for more torque. I could really care less about speed. I like wheelies and acceleration. Don't have the room for running wot much. Lot's more to come in the next week or so.