It's not really an exact science.
But what is it youÃ¢â‚¬â„¢re looking for. Are you looking for an off road rugged terrain kind of thing or a nice fast lawn cart?
I built one and shortly after that I tore it apart and there it sits because it wasnÃ¢â‚¬â„¢t what I wanted. When I built it, it was a lawn cart. I think it would do about 20+ no prob. and that was fast for dudlin around the yard but I couldnÃ¢â‚¬â„¢t take it off road and I wanted an off road cart.
I ended up taking a chain driven 4 wheeler rear end and welding it up to the cart frame. I havenÃ¢â‚¬â„¢t gotten it back together yet because I need a hub for the axle and I need rims and tires.
I should just bye the stupid things and get it over with.