Green’s Dictionary of Slang

dubs n.³

(US black/campus) 20-inch tyre rims.

2003		50 Cent ‘In da Club’ 🎵 When I pull out up front, you see the Benz on dubs.
2003		Eble Campus Sl. Nov.
2013		T. Pluck ‘Junkyard Dog’ in Life During Wartime (2018) 204: ‘You know how much these dubs cost?’ ‘They ain’t dubs, Cee [...] They eighteens’.
2021		T. Pluck Boy from County Hell 124: ‘[O]ne of those old hoopties you boys like to put dubs on’.

In phrases

sit (on) dubs (v.)

of a car, to have 20-inch tyre rims.

2003		Eble Campus Sl. Nov. 6: sit on dubs – for a vehicle to have 20 inch rims: Tom was driving a new S.U.V. sitting on dubs.
2004		Sth Florida Sun Sentinel (Ft Lauderdale, FL) 16 Apr. 324/1: [advert] This car is your means to the future. Sitting on dubs, sound system blaring, tinted windows.
2007		Clarion Ledger (Jackson, MS) 1 July 29/9: Dodge Magnum ’07 22K, Sitting Dubs.