Running Lights Technical Page

Please assess carefully your level of technical skill in figuring out what you want to do. You can do more damage by cutting your wiring harness and soldering it poorly than any benefit from adding a device. Figure out what has to be done, and if it is beyond your skills, get the job done by a professional bike mechanic.

To choose the type of running light, first assess your bike alternator to figure out if it can generate enough power to run your new lights.

For incandescent, PIAA or HID lights, take the wattage, multiply by 2 (for two lights) and divide by the voltage. A pair of 55-watt halogen lights, for example, would need 110/12 amps at 12 volts, or about 9 amps.

Consult the bike manual find the alternator capacity in amps, and subtract the amperage of the ignition, lights and other always-on lights. A good bet here is usually to get on an owners forum for your bike and finding someone who has already worked it out. Or check out's bike registry.

Some bikes just don't have enough juice for incandescent, PIAA or HID lights, but LED technology can provide the answer. You might be able to free up enough capacity by replacing turn signal, brake, tail and/or license plate with LEDs.

If not, you can always use an LED running light.

Choosing an incandescent, PIAA or HID light.

This is largely a matter of budget and taste. I have had good results by getting a pair of lights cheap at a discount store and mounting them on the outside of my crash bar. This provides a wider profile than mounting on forks or inside the crash bars. We are interested in getting the lights as wide and low as possible, to aid drivers in estimating our closing speed, and we don't worry too much if we drop the bike on a cheapie, $18 light.

The most important feature is to not get a fog light or other focussed light. We want the beam to spread for maximum visibility.

Choosing an LED light.

LED lights have improved recently. A set of three 'Super LEDs' are brighter than thirty or more of the old-style LEDs. For $90 or so, you can get a pair of triple 'Super LEDs' made for police marker lights and they are very bright. You can also get LEDs running lights in popular Web car accessory sites, or, my favorite, by stopping at a truck stop. Accessories for bikes always cost too much. LEDS, unlike regular lights, shoot light straight out, so, for conspicuity, you probably want a refractive rather than a clear or focussed lens.


If you are lucky, your bike might be equipped with mount points for running lights, in which case consider adding a relay and follow the instructions.

In most cases, it is best to install a relay to take power from the battery and trigger the relay on the high beam headlight hot wire. See the relay page for more details. You can figure out which wire by consulting the shop manual, asking on your model owners forum, or by looking at the back of the headlight and experimenting. The relay is needed because bikes have a circuit to cut off the headlight when the starter is cranking, and if we omit the relay, the running lights will stay on, reducing the battery amperage available for the starter motor.

If you are expert enough to cut the hot high beam wire and solder on a feed to the relay, consider that, or use a wire tap device, or consult a professional. The negative feed can come direct from the battery. All solder joints should be shrink-wrapped, and any exposed cables should be protected with tubing and routed away from moving bike parts and hot components.

Mounting the lights depends on your configuration. A wide variety of bar mounts can be bought in online bike gadget stores, or a little ingenuoty with sheet metal and u-bolts can work wonders.

LED lights are usually polarized. They won't work if the positive and negative wires are swapped, but regular incandescent bulbs usually don't caree. Led lights often come with all sorts of small additonal electronics, which probably should be retained.

Many riders like to also add a switch in one of the light wires, so the light can be forced off if required.