BMW Motorcycle K1100RS front and rear turn signal bulbs utilize a P21W size. The replacement chart covers 1993 to 1996 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 K1100RS uses the P21W bulb type across all documented 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 signals and brake lights.
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 K1100RS turn signal sockets.
The ECE standard classification of the P21W means the bulb conforms to United Nations Economic Commission for Europe regulations, a specification widely adopted across European and international vehicle markets.
The K1100RS front and rear turn signals share the same P21W specification across the 1993-1996 model years, meaning both positions draw from the same bulb type.
At 21 watts, the P21W produces a relatively high light output for a single-filament bulb, which is a characteristic intentional to the signalling function it serves.
Substituting a dual-filament bulb such as the P21/5W into a BA15s socket is not supported by the K1100RS specification, as the socket is designed for single-contact fitment only.