BMW Motorcycle R850C front and rear turn signal bulbs use 12496, P21W, or PY21W bulb sizes. The replacement chart covers 1996 to 2001 model years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The BMW Motorcycle R850C turn signal system relies on three bulb types across its 1996-2001 model years: the 12496, P21W, and PY21W. All three operate at 12 volts, making them consistent in electrical demand across the platform.
The P21W is an ECE-standard single-filament signalling bulb rated at 21 watts and fitted with a BA15s bayonet base. It serves as the clear-lens turn signal bulb for both front and rear positions across all six model years in the specifications.
The PY21W shares the same 21-watt single-filament construction as the P21W but produces amber-tinted light from the bulb itself and uses a BAU15s bayonet base. The BAU15s base is offset, meaning it is not physically interchangeable with the straight BA15s base of the P21W despite the otherwise similar appearance of the two bulbs.
The 12496 is a Philips/Osram part number designating a 12-volt halogen bulb for specialty applications. It appears in the clear-lens positions for certain model years as an alternative to the PY21W, serving the same amber signalling function through a different product line.
Lens type is a direct factor in bulb selection for the BMW Motorcycle R850C. Clear-lens housings require a bulb that produces amber light on its own, either through an amber-coated envelope as in the PY21W or through the 12496. Non-clear-lens housings use the P21W, which relies on the lens itself to produce the amber signal color.
The front and rear turn signal positions do not always share the same clear-lens bulb type within a given model year. In 1997 and 1999, the front clear-lens position calls for a PY21W while the rear clear-lens position in 1997 calls for a 12496, illustrating that the two positions must be treated independently when selecting bulbs.
Substituting a P21W for a PY21W or 12496 in a clear-lens housing would result in a white signal output rather than the amber output required by ECE signalling standards, as the P21W produces no amber tint of its own.
The BAU15s base of the PY21W has its contact pins offset at an angle, a deliberate design feature that prevents the bulb from being seated into a BA15s socket. This physical incompatibility between the two base types is a built-in safeguard against incorrect bulb installation in lens-dependent versus self-colored signalling applications.