The Triumph Thunderbird ABS front and rear turn signal bulbs use a 12496 or PY21W size. The replacement chart covers 2010 to 2013 model 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 PY21W is the most frequently specified bulb across the Triumph Thunderbird ABS turn signal positions and years. It follows the ECE standard used in Europe and worldwide markets, operates at 12V with a 21W output, produces an amber light from a single filament, and uses a BAU15s offset bayonet base. The offset pin arrangement of the BAU15s base is a deliberate anti-misfit feature, preventing the bulb from being seated in sockets designed for other bayonet types.
The 12496 is a Philips/Osram part number designation for a halogen bulb rated at 12V and classified as a specialty application type. It appears in both the front and rear turn signal positions across the 2010-2013 model years, though not uniformly across all positions or years.
The front turn signal position on the Triumph Thunderbird ABS uses the PY21W for the 2010-2011 model years and transitions to the 12496 for 2012-2013. These two bulb types are not interchangeable due to differences in base design and application classification.
The rear turn signal position follows the inverse pattern. The 2010 model year specifies the 12496, while the 2011-2013 model years specify the PY21W. This means the front and rear positions on the 2012-2013 models use the same bulb type, whereas the 2010 model uses different bulb types depending on position.
The 2011 model year is the only configuration in which both the front and rear turn signal positions share the same bulb type, with PY21W specified for both locations.
Because the 12496 and PY21W are distinct bulb types with different base configurations and application ratings, substituting one for the other in any position or year would not constitute a direct fitment match according to the specifications provided.