BMW Motorcycle K100RS front and rear turn signal bulbs utilize a P21W size. The replacement chart covers 1983 to 1989 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 BMW Motorcycle K100RS uses the P21W bulb type across all listed model years (1983-1989) for both front and rear turn signals.
The P21W is an ECE-standardized bulb, meaning it conforms to a regulatory framework recognized across Europe and numerous other markets worldwide.
P21W bulbs operate on a 12-volt electrical system and draw 21 watts, which is a wattage rating typical of single-filament automotive signaling applications.
The single-filament design of the P21W means it serves one lighting function only, distinguishing it from dual-filament variants that combine two functions such as braking and turn signaling within one bulb.
The P21W uses a BA15s bayonet base, where "BA15" refers to the 15mm pin spacing of the bayonet cap and "s" denotes a single contact at the base, confirming its single-filament configuration.
The BA15s base is not interchangeable with the BA15d base, which carries two contacts and is used for dual-filament bulbs. Substituting one for the other is not possible without modification.
The front and rear turn signals of the BMW Motorcycle K100RS share the same P21W specification across all listed years, indicating a uniform bulb fitment throughout the entire production run covered by these specifications.