Chevrolet Chevelle Tail Light Bulb Size

Additional Notes

• The 1157 is the tail light bulb size for the Chevrolet Chevelle across all listed model years, spanning 1964-1973.
• The 1157 bulb is an ANSI-standardized type, meaning its physical and electrical specifications are defined by a recognized North American standards body and are consistent across manufacturers.
• As a dual-filament bulb, the 1157 contains two separate filaments within a single envelope, allowing it to serve two distinct lighting functions from one unit, typically stop and tail light operation.
• The 1157 operates on a 12-volt electrical system, which is standard for automotive applications of this type.
• Its two filaments are rated at 21 watts and 5 watts respectively, with the higher-wattage filament producing the brighter output used for braking signals and the lower-wattage filament providing the dimmer running light output.
• The 1157 uses a BAY15d bayonet base, a two-pin offset base design that prevents incorrect installation by ensuring the bulb can only be seated in one rotational orientation, aligning each filament with its corresponding circuit contact.
• The BAY15d base is a widely produced standard, meaning 1157 bulbs from different manufacturers are physically interchangeable in the Chevelle's tail light sockets across all listed years.
• Because the same bulb number applies to the Chevrolet Chevelle from 1964-1973 without variation, no year-specific fitment distinctions exist within this range for the tail light position.