BMW Motorcycle R1150RT front and rear turn signal bulbs utilize a P21W size. The replacement chart covers 2001 to 2005 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 R1150RT uses the P21W bulb type across all listed model years (2001-2005) for both front and rear turn signals.
The P21W is a single-filament bulb, meaning it serves one lighting function only, which is consistent with its dedicated turn signal application on the R1150RT.
P21W bulbs operate at 12 volts and 21 watts, placing them in the standard low-voltage automotive range typical of 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 "s" indicates a single contact at the base.
The BA15s single-contact base is not interchangeable with the BA15d base, which carries two contacts and is found on dual-filament bulbs such as the P21/5W.
The P21W is an ECE-regulated standard, meaning its output and construction conform to Economic Commission for Europe requirements recognized across European and many worldwide markets.
Because the R1150RT (2001-2005) uses the same P21W specification for both front and rear positions, the bulbs are physically interchangeable between those positions.
LED replacements for the P21W with a BA15s base are available on the aftermarket, though motorcycle turn signal circuits without a load equalizer may exhibit rapid flashing when lower-wattage LED units are installed in place of the original 21W bulbs.