Handlebar or Helmet mounted systems? For road use, lights need to be attached to the actual bike, but for off-road a head mounted lamp is definitely the way forward, used either alone or along with a handlebar mounted one. If lamps are mounted too low, the merest bump in the trail can create a large pool of shadow that could be concealing anything. What’s more, on twisty single track, the handlebars are not always pointing in the direction that you want to look in.
Helmet mounted lights get around these problems, and are also a great bonus when repairs are required. There is great scope for cross-over usage, be that adventure racing or crawling under the floorboards looking to fix that draught. The only downside with head-mounted lights comes when it is misty; in these conditions the light scatters off particles close to the eyes, and it can be difficult to see the ground ahead. In these conditions, a back-up handlebar lamp can be very useful.
There are currently 3 main types of bulbs used in high-power off-road lighting systems: Halogen, Metal Halide and Light Emitting Diodes (LEDs).
By far the most established light-source in the off-road lights market, halogen lamps belong to the incandescent family, in that the light is produced by passing an electric current through a filament. The resistance to the electrical current causes the filament to heat up to such an extent that it emits light. This process is contained within a chamber filled with various inert gases which enhance the performance of the filament and prevent it from burning out by reacting with oxygen.
Some manufacturers gain even higher performance from their bulbs by a process known as over-volting. By attaching for example a bulb designed to run at 12 volts to a battery producing 13.5 volts rather than 12 volts, the bulb will produce a comparative increase in both brightness and colour temperature. This improvement comes at the price of a shortened bulb life, but the benefits are generally considered to outweigh this.
Halide lamps are arc types in that the discharge of an electrical arc between two electrodes produces light. Performance is increased by the addition of metal halide vapours into the chamber or discharge tube surrounding the electrodes. Because the vapours in the discharge tube are under high pressure, these lamps are also sometimes called High Intensity Discharge (HID) lamps. These lamps represent the pinnacle of bulb technology, and similar systems are to be found in soccer stadium flood-lights. They produce a characteristic hard white light (high colour temperature) and have a longer life span than Halogen lamps.
With so many positive attributes one might wonder why anyone would still bother with halogen bulbs, but of course there are some draw-backs too. As with emerging battery technology, the forefront of bulb research and development comes with a hefty price tag, and you can currently buy an entry-level bike for less than some of the lighting systems using these bulbs. Because the circuitry employed to initially create the arc takes time to reset itself, these lights cannot be switched on and off at will, and the life-span of the lamp is affected by the number of ignition cycles.
Not so much a bulb as a piece of electronic circuitry, LEDs are an attractive proposition for bike lighting because of their extreme energy efficiency. The units themselves are nothing new, and started appearing in bike rear lights in the 1980’s. Because of the lack of suitable “white” units, early front LED lights used fairly ineffective yellow or green LEDs. More recently, higher output white LEDs have become available/affordable, and there are many who predict that the future of off-road lighting lies down this path. The technology is still developing, so it is pricey and there remains scope for improving the brightness.