BMW Motorcycle R1100GS front and rear turn signal bulbs use a P21W size. The replacement chart covers 1994 to 1999 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 is the sole bulb type specified for the BMW Motorcycle R1100GS across all listed turn signal positions, covering model years 1994-1999.
The P21W is a single-filament bulb, meaning it serves one lighting function only, which is consistent with its dedicated use in turn signal applications rather than combined stop/tail assemblies.
The P21W operates at 12 volts and 21 watts, a wattage rating that falls within the standard range for turn signal bulbs on 12-volt motorcycle electrical systems.
The P21W uses a BA15s bayonet base, where "BA" denotes a bayonet cap fitting, "15" refers to the 15mm base width, and the lowercase "s" indicates a single contact at the base.
The BA15s base is a single-contact design, which corresponds directly to the single-filament construction of the P21W and distinguishes it from the dual-contact BA15d base used on two-filament bulbs.
The P21W carries ECE certification, indicating it meets the Economic Commission for Europe lighting regulations accepted across Europe and numerous other markets worldwide.
Both the front and rear turn signal positions on the R1100GS share the same P21W specification across all listed years, meaning the same bulb type is interchangeable between the two positions on this model.
Because the BA15s base is a keyed single-contact fitting, substituting a BA15d base bulb is not a compatible replacement, as the pin and contact configurations differ between the two base types.