Talk w/ Me, Not t/ Me?

Is there a rule for putting a space after "w/" when it represents the word "with"?

There's a space after the slash just as there's a space after every word. (But, why would you abbreviate a tiny little word like "with"?)
Is there a rule? I'd be hard pressed to find a specific rule in any of my style books, so logic wins over style.
T/ 4 rit/