The Triumph Speed Four uses a 9003 bulb size for both high beam and low beam headlight applications. The replacement chart covers 2002 to 2006 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 Triumph Speed Four uses the 9003 bulb size across both the high beam and low beam headlight positions for the 2002-2006 model years.
The 9003 is a dual-filament halogen bulb, meaning a single bulb contains two separate filaments to serve both high and low beam functions within one unit.
Because both headlight positions on the Speed Four share the same 9003 specification, a single bulb type serves the entire headlight assembly.
The 9003 operates at 12 volts, with a wattage rating of 60W on the high beam filament and 55W on the low beam filament.
The 9003 bulb uses a P43t base, which is a bayonet-style mount with a 43mm flange width, and fitment requires a socket compatible with this base type.
The 9003 designation follows the ANSI standard used in the United States and Canada. It is electrically and physically equivalent to the international H4 bulb, though the designations originate from different standardization bodies and packaging may differ by market.