The Triumph Bonneville Bobber headlight bulb uses a 9003 size for both high beam and low beam functions. The replacement chart covers 2017 to 2018 vehicle 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.
The 9003 is the sole bulb type specified for the Triumph Bonneville Bobber, serving both the high beam and low beam headlight positions across the 2017-2018 model years.
The 9003 is an ANSI-standard dual-filament halogen bulb, meaning a single bulb contains two separate filaments: one rated at 60W for high beam operation and one rated at 55W for low beam operation.
The bulb operates on a 12V electrical system, which is standard for motorcycle applications of this type.
The 9003 uses a P43t base, a specific bayonet-style fitting that determines physical compatibility with the headlight housing.
The 9003 designation is an ANSI classification recognized in the United States and Canada. It is functionally equivalent to the ECE-standard H4 bulb, though the two designations originate from different regulatory frameworks and packaging may differ by market.
Because the same 9003 bulb is specified for both the high beam and low beam positions, the Bonneville Bobber uses a single-bulb headlight system rather than separate bulbs for each function.