This section gathers the comprehensive range of bulb specifications used across classic-MG production, every type of bulb fitted to the cars, from the large headlamp bulbs through the indicator and brake-light bulbs to the small instrument-panel and interior bulbs, each fitting type and electrical specification stocked in the appropriate variants. Carrying a spare bulb kit is recommended, as a failed headlamp or rear lamp bulb discovered after dark can leave the car stranded or illegal to drive, and a spare bulb kit is a legal requirement for touring in several European countries.
Tungsten Specifications
Tungsten bulbs, the traditional filament construction used through the bulk of classic-MG production, are stocked in the original specifications appropriate to each application. Single-contact bayonet bulbs cover the indicator and side-lamp applications in 21-watt and 5-watt specifications, offset-pin double-contact bulbs cover the combined brake-and-tail-light applications in 21/5-watt, festoon bulbs in various lengths cover the interior courtesy-light applications, and capless and small bayonet bulbs cover the various instrument-panel illumination points, each matched to the specific fitting and electrical specification of the application with the standard wattages reflecting the original equipment. For concours restoration to factory-original specification, period-correct tungsten bulbs are the appropriate choice.
Headlamp & Halogen Specifications
Headlamp specifications vary across the range, the earliest cars using a bayonet pre-focus bulb in the original Lucas headlamp units rather than a sealed-beam or a modern H4, so an H4 halogen bulb will not fit an original pre-focus lamp without an adaptor or a modern replacement lamp unit. Halogen bulbs offer substantially better light output than the equivalent tungsten specifications and are stocked as direct-replacement alternatives, H4 twin-filament bulbs for dipped and main beam on cars with modern lamp units, H7 single-filament bulbs for later and aftermarket lamps, and H1 and H3 bulbs for auxiliary fog and driving lights, available in standard specification and in premium ranges such as Osram Nightbreaker for maximum output and All Season with a warmer beam that performs better in rain and fog.
When fitting halogen bulbs at higher wattages the additional current draw exceeds the rating of the original light switch and harness, so a headlamp relay kit should be fitted to take the high-current load off the switch and wiring, and halogen bulbs should always be fitted in matched pairs as bulbs of different brightness produce uneven output.
LED Alternatives & Fitting
LED bulbs are stocked as direct replacements for the various tungsten specifications, using the same physical fitting and electrical connection but delivering brighter, more consistent illumination with substantially lower current draw and many years of service life, the practical answer for cars used regularly on modern roads. LED indicator bulbs, however, require either a compatible LED flasher relay or load resistors to flash at the correct rate, as the reduced current draw causes a standard thermal flasher unit to flash too fast or not at all. Headlamp and halogen bulbs must be handled without touching the glass envelope, as fingerprint oils leave deposits that become hot spots during operation and significantly shorten bulb life, and if the glass is touched accidentally it should be cleaned with methylated spirit on a lint-free cloth before fitting. A standalone capless bulbholder is stocked for push-in instrument and panel positions where the original holder has corroded or embrittled, often restoring a faulty illumination circuit that a new bulb alone would not resolve.