Triumph TR6 Back Up Light Bulb Size

The Triumph TR6 back up light utilizes bulb size P21W and bulb size 1156 for illumination. Available data for the specific components covers the range from 1969 to 1976.

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	US Type	EU Type	Shop
1969-1976	1156	P21W	Check Price

Bulb Specifications

Description	Type	Shop
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156	Check Price
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W	Check Price

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Additional Notes

The Triumph TR6 uses the 1156 bulb across all listed model years, spanning 1969-1976, for the back up light position.
The 1156 is an ANSI-standardized bulb type recognized in both the United States and Canada, meaning it conforms to a defined set of electrical and physical parameters shared across manufacturers.
The 1156 operates on a 12-volt system and draws 21 watts, which places it in the range typical of incandescent automotive signal and reverse lighting applications.
The bulb uses a BA15s bayonet base, a single-contact fitting where the "s" denotes a single pin, as opposed to the dual-pin BA15d base found on double-filament variants.
The 1156 carries a single filament, which means it serves one lighting function only. This distinguishes it from visually similar bulbs such as the 1157, which has two filaments and a BA15d base and is not interchangeable with the 1156 despite sharing a comparable physical profile.