How do you unlock all vehicle custimizations in Mario kart 7?

Answer 1

There isn't really a "fastest kart", as it all depends on preference. One thing to consider is that you usually want to focus more on acceleration than speed, and this is because if you have acceleration, you can recover faster from getting hit with an item, which happens quite a bit. Also, each character has it's own advantages and flaws, so it all depends on the player. My personal favorite is Luigi, Bruiser, Wood wheels, and the Beast glider. Not all of these are unlocked at the beginning of the game however.