I have noticed that the Rhino(the tank) takes pretty long to get up to speed. So I found out a way to make it faster.
First, hold down the WHITE AND BLACK buttons at the SAME TIME, to make the barrel point behind you. Then, without letting go of the buttons, press the BACK button to change your view(you want the one where it shows no vehicle at all, nose cam) then release the black and white buttons. Then when you are driving, and you want more speep, just hit a or b to fire and it will make you go faster. OF course your going to blow up what ever is behind you.