NASCAR Racing: I need your help., street cars, air dam

Question
QUESTION: Hi, I wanna know about the rear bumper that is like knives like this shape " |||| ". What's the main benefit of this bumper ? Handling or Aerodynamic or Air Piercing ? And the benefit of the front air dam.

ANSWER: HI MJ,

i need to know a little more about the bumper, is this nascar or streetcar?  if it is nascar, is it chevy, dodge, toyota, or ford?

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QUESTION: street car

Answer
I do not know much about street cars.  A larger and wider bumper normally helps with handling.  But areo package is mostly helped by the front nose.  The more wedge like the car is the more aerodynamic advantage it has.
Sorry i couldn't be of more help
Coy Jordan