Drag cars are narrow to reduce drag coefficient. Tractors don't go fast enough to worry about that. Just make sure it's narrow enough to fit in your trailer 
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While thats part of the equation its not the entire story. That doesnt explain why the rear wheels on a top fuel funny car sit about a foot inboard of the body panels. flush or just inside of flush with the panels would create the most efficient air flow around the tires with less turbulent eddie currents and much more laminar airflow. the tires are that far inboard to help the car go in a straight line. its simple physics. heres a way to think about it that should be simple take a 10' pole [something like a black iron pipe] and weld a 3' bar as a tee on one end. lay the pole out straight infront of you with the far end touching the ground. grab that tee with your hands as close together as possible. try to point the bar left or right, its going to be pretty hard to slide the tip of the pole either way. hold you hands all the way out on that 3' bar and then try to point it left or right. way way easier. its simple leverage. you didn't magically get stronger but it sure got easier to turn things. you tractor chassis is the pole and your rear axle with is the 3' bar. your hands are the tires and your muscles are the horsepower. simple physics a longer pole will also go straighter and a pole with all it's mass at the far end will be even harder to turn. so as narrow as possible, as long as possible[legal], as nose heavy as possible [just dont over kill it with the nose weight just load the nose first before you fill the belly bar] |
