actually, you can accelerate harder IN THE GAME when leaning back, with or with out being tucked in. i know this because i raced a ghost in a straight line, and the wheelie won...now RL is different. leaning foward to reduce the weight over the back tyre will help you accelerate faster, because your pushing the front tyre down while the rear is trying to pull it up. in the game it is as simple as tt will only let the bike accelerate to the point where it is about to wheelie, but wont unless you hold the left thumbstick down.