Triumph TR8 front turn signal bulbs use P21W size while rear turn signal bulbs use 1156 size. The replacement chart covers 1980 to 1981 production years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The P21W and 1156 bulb types appear across all listed years (1980-1981) for the Triumph TR8, making them the two bulb types relevant to this vehicle's turn signal system.
The P21W is governed by ECE standards, which apply primarily in Europe and worldwide markets, while the 1156 follows ANSI standards used in the United States and Canada. Both serve as single-filament signalling bulbs rated at 12V and 21W.
Despite originating from different standardization bodies, the P21W and 1156 share the same BA15s bayonet base, identical voltage rating of 12V, and identical wattage of 21W.
The Triumph TR8 (1980-1981) uses the P21W for the front turn signal positions and the 1156 for the rear turn signal positions, meaning the two bulb types are not interchangeable between front and rear housings by specification.
The BA15s designation refers to a single-contact bayonet base with a 15mm collar, distinguishing it from the dual-contact BA15d variant. The single-contact design is consistent with single-filament operation, as no second filament requires an additional electrical contact.
Although the P21W and 1156 share physical and electrical characteristics, their differing regulatory origins can result in subtle manufacturing variances between individual units from different suppliers, which is relevant when sourcing replacements across market regions.