Refers to the tightness of a girl's vagina. If a girl has a loose vag, she is said to have very little (if any) tread on her tires.
Hey, how was hooking up with Sarah last night?
Let's just say there's no tread on the tires.
She was that loose?
It was like throwing a hot dog down a hallway.
Gross.
Someone is is so incredibly sleepy, they are using a slant rhyme of "Tired Liger" to show how sleep deprived they are. They are also referring to a mystical animal like a liger because they want to have dreams with magical animals in them.