BMW Motorcycle R45 front and rear turn signal bulbs utilize a P21W size across all applications. The replacement chart covers 1978 to 1985 model 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 BMW Motorcycle R45 uses the P21W bulb type across all listed model years for both front and rear turn signals.
The P21W is an ECE-standard single-filament bulb rated at 12 volts and 21 watts, designed for signalling applications such as turn indicators.
P21W bulbs use a BA15s bayonet base, which is a single-contact bayonet fitting with a 15mm collar width.
The BA15s base designation indicates a single-contact configuration, distinguishing it from the dual-contact BA15d variant, which is not interchangeable with the R45's turn signal sockets.
The R45 front and rear turn signals share the same P21W specification across the 1978-1985 model year range.
The ECE designation on the P21W confirms the bulb meets European and international regulatory standards for road use, as opposed to SAE-standard bulbs common in North American markets.
At 21 watts, the P21W produces sufficient luminous output for turn signal visibility while remaining within the low-current demands typical of motorcycle electrical systems of that era.