Harley-Davidson FXSB Low Rider - Belt Tail Light Bulb Size

Harley-Davidson FXSB Low Rider - Belt uses a 1157 bulb size for the tail light assembly. The replacement chart covers 1983 to 1984 production years with corresponding bulb size specifications.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
1983-1984	1157

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. 12V, 21W/5W.	1157

Other Locations

Additional Notes

The 1157 is a dual-filament bulb, meaning it serves two lighting functions within a single unit. The higher-power filament at 21W handles the brake or turn signal function, while the lower-power filament at 5W handles the running or tail light function.
The 1157 operates on a 12-volt electrical system, which is standard for the automotive and motorcycle applications it was designed to serve.
The 1157 uses a BAY15d bayonet base, a two-pin offset base that physically prevents incorrect installation. The offset pin positions ensure the bulb can only be seated in one orientation, keeping the two filaments correctly aligned with their respective circuits.
The 1157 is an ANSI-standardized type, recognized across the United States and Canada, meaning physically and electrically equivalent units from different manufacturers are interchangeable within that standard.
The Harley-Davidson FXSB Low Rider - Belt used the 1157 bulb for the tail light position across both the 1983-1984 model years.