Tired or Exhausted

Okay, TheKnightMusic, listen up. You are clearly not the sharpest tool in the shed. The joke plays on the words "tired" and "exhausted", which sound similar to the words "tire" and "exhaust". When you run next to a car you get tired, but when you are behind it, you are behind the exhaust which is exhausting. It's wordplay, you get it? It's not rocket science!