Triumph Thunderbird LT Turn Signal Bulb Size

The Triumph Thunderbird LT uses 12496 and PY21W bulb sizes for both front and rear turn signal applications. The replacement chart covers 2014 through 2017 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.

Front Turn Signal

If US Type and EU Type show the same value, a direct cross-reference for this bulb is not available or the data is insufficient.

Years	US Type	EU Type	Shop
2017	12496	12496	Check Price
2016	7507	PY21W	Check Price
2014	7507	PY21W	Check Price

Rear Turn Signal

If US Type and EU Type show the same value, a direct cross-reference for this bulb is not available or the data is insufficient.

Years	US Type	EU Type	Shop
2017	12496	12496	Check Price
2016	7507	PY21W	Check Price
2014	12496	12496	Check Price

Bulb Specifications

Description	Type	Shop
Philips/Osram part number. Halogen bulb, specialty application. 12V.	12496	Check Price
ECE standard (Europe & worldwide). Single-filament amber bulb with BAU15s bayonet base. 12V, 21W.	PY21W	Check Price

Other Locations

Additional Notes

The PY21W is an ECE-standardized single-filament amber bulb operating at 12V and 21W, fitted with a BAU15s bayonet base. The offset pins of the BAU15s base are a deliberate design feature that prevents substitution with non-amber bulbs sharing a similar base type.
The 12496 is a Philips/Osram part number designating a 12V halogen bulb intended for specialty automotive applications. It is not an ECE or SAE universal code, meaning it references a manufacturer-specific product rather than a broad bulb category.
The Triumph Thunderbird LT (2016) uses PY21W bulbs in both the front and rear turn signal positions, making it the only model year in these specifications where both positions share the same bulb type.
The 2014 Thunderbird LT uses PY21W at the front turn signal but 12496 at the rear, meaning the two positions are not interchangeable for that year despite both operating on 12V circuits.
The 2017 Thunderbird LT uses the 12496 bulb in both the front and rear turn signal positions, differing from the 2016 fitment at both locations.
Because the 12496 and PY21W are distinct bulb types with different base configurations and physical forms, substituting one for the other is not supported by these specifications, even where voltage ratings align.