The root of dubs stems from the term doves. Doves, inturn, is used to describe 1 gram of marijuana. A "flock of doves" is 1 ounce of marijuana in individual 1 gram "dime" bags prepared to be sold. The transistion from marijuana to wheels might be from the ostentatious cars driven by successful drug dealers.
Hook me up wit a dub (a.k.a. dove, dime ) of da sticky-icky.