The GMC C1500 Suburban brake light utilizes unique bulb sizes 3057, 2057, and 1157 depending on the specific production period. Data for the provided components covers the range from 1979 to 1999.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The GMC C1500 Suburban brake light specifications cover three distinct dual-filament bulb types across the 1979-1999 model years: the 1157, 2057, and 3057.
The 3057 is the most frequently specified brake bulb in these records, covering the 1992-1999 model years. It is an ANSI-standard dual-filament wedge bulb in a T25 form factor, rated at 12V with a 27W high-filament and 7W low-filament output.
The 1157 and 2057 both use the BAY15d bayonet base, which is a two-pin offset base that physically allows one bulb to substitute for the other in some housings. However, their wattage ratings differ, and substitution without confirming socket and circuit compatibility is not advised.
The 1157, specified for the 1979-1982 model years, operates at 12V with a 21W high filament and 5W low filament. It is one of the most widely used automotive bulb types in North American vehicles of that era.
The 2057, specified for the 1983-1986 model years, shares the BAY15d base with the 1157 but draws 26.9W on its high filament and 8W on its low filament, making it a higher-output variant of the same base type.
The 3057 uses a wedge base rather than the BAY15d bayonet base found on the 1157 and 2057, meaning the 3057 is not physically interchangeable with either of those two bulb types despite serving the same brake light function.
The 921 is a single-filament wedge bulb in a T15 form factor, rated at 12V and 16W. Its single-filament design reflects its dedicated stop-light-only role in the center high mount stop light, which does not require a combined stop and tail function.
The 921 center high mount stop light is specified for the GMC C1500 Suburban across the 1993-1997 model years. This position is a separate lighting circuit from the rear brake lights and uses a physically smaller wedge base than the T25 3057.
All four bulb types in these specifications conform to ANSI standards applicable in both the United States and Canada, indicating standardized electrical and photometric performance requirements across that market.
The 3057 and 921 both use wedge bases but are not interchangeable with each other, as the T25 and T15 designations indicate different bulb body sizes that correspond to differently sized sockets.