[Samwise]

I've heard it.

You can't comb your hair with a wagon wheel. The expression means "You need to comb your hair. It's a mess."

[agrace]

HA, I should have been clearer. I understood it, in that my dad meant my hair was a mess, just didn't understand why a wagon wheel was a good descriptive tool. I guess you could replace it with anything, such as "you look like you combed your hair with a garbage bag," or "you look like you combed your hair with a water glass" - those would make about as much sense.

Wait, did you just say that you've actually HEARD that? Where did you grow up?

[Richard Kimball]

It comes from here:

Now old Dan Tucker's fine old man
Washed his face in a fryin' pan
Combed his head with a wagon wheel
And died with a toothache in his heel

Get out of the way old Dan Tucker
Get out of the way old Dan Tucker
Get out of the way old Dan Tucker
You're too late to get your supper

Now old Dan Tucker is come to town
Riding a billy goat leading a hound
Hound dog bark and the billy goat jump
Landed Dan Tucker on top of the stump

Now old Dan Tucker he got drunk
Fell in the fire and kicked up a chunk
Red hot coal got in his shoe
And oh my lawd how the ashes flew

Now old Dan Tucker is come to town
Swinging the ladies round and round
First to the right and then to the left
Then to the girl that he loves best