It's rare, I know, but occasionally something happens in the car world that is truly useful to us. And I don't mean the fitment of Radar, Bike Proximity Warnings or even the simple, all encompassing Driving like a Clown warning. Which isn't on the market yet but I'm planning on getting it out there soon. And retiring very shortly afterwards, because it's a winner. But I digress. No, the particular device I'm thinking of is HID headlights, also referred to as Xenons. Because that's the gas inside them.

HID lights first appeared on top end cars about ten years ago. They have a characteristic blueish light that's very close to daylight and consequently works better with your eyes. They're also notably brighter, I think because they get around the DTp headlamp wattage restriction by being, in fact, very low wattage indeed. But a 35W HID lamp will melt your eyeballs at a thousand paces, so the 55W limit imposed by the powers that be isn't really a problem.

The problem with fitting these lights to bikes was, until recently, threefold. First of all, though there are some which dip, they're not very good. A mechanical shield gets moved by a servo and...oh, it's just complicated and horrible. And ruinously expensive. So unless your bike has separate high and dip beam lights, you're in trouble. The next problem was the cost. Five years ago having them fitted to my car would have cost me £1200. Which is a bit steep. The third problem was the bulk, and to explain that we need to look at how they work.

A normal bulb has a piece of wire, called a filament, inside a glass capsule containing some sort of inert gas. That gas is normally a halogen like iodine, and the glass is made from quartz. When electricity is passed through the filament it heats up and glows. The higher the resistance of the wire, the hotter it gets and the higher the power (wattage) of the bulb. In fact it gets white hot - that's what the gas is for. If it was in air the wire would burn away in seconds. An HID lamp doesn't have that filament. Instead it has a capsule of gas and a couple of electrodes. The electrodes get a very high voltage across them - 23,000v in this case - which excites the gas in the tube and makes it glow. The same thing happens with fluorescent lights at home and with neon lights in Piccadilly Circus, just with different gases. Xenon happens to emit a very bright, blue-white light under these conditions. Which is rather handy for us. But you may have noticed that your bike electrics don't, as a rule, produce that sort of voltage. For that you need a power supply, called a ballast. And they're rather big.

Recently a few things have happened to make HIDs accessible to the bike market. First of all, more and more bikes now have twin lights with one working as dip and one as high beam. Second, the lights became more common on cars and increased numbers means reduced cost. And ballasts have got much, much smaller and lighter.

But the main thing that happened was that an enterprising company in Yorkshire decided to sell them as singles instead of pairs. And to target them at bikers.

To explain what's so good about them, take a look at the picture above. On the right is the main beam lamp in my car. It's illegally powerful at 130W but it works quite well. On the left is a 35W HID. The difference in brightness is obvious, and the light is clearly much, much whiter as well. As I said earlier, our eyes are designed to work best in daylight so light which is closest to daylight in colour makes it easier and less tiring to see things at night. Oh, I used my car rather than the bike because the bike lights are too close together and just don't photograph very well.

So let's assume that you're a convert to HIDs and would like to fit them to your bike. That's actually a lot less difficult than you might think. The first thing you need to do is contact the supplier - www.hids4u.co.uk - and let them know what your bike is and whether you want dip beam, main beam (you probably don't) or both (my word, you are feeling flush). A couple of days after placing your order you'll receive a large box in the post. First strike for them - packing and presentation are both excellent. Take the instruction leaflet and read it. Realise how easy this is going to be. Take the old headlight bulb out and put the new lamp in. Remember to take it out of the foam wrapper first. Connect the spade connectors on the wire from the ballast to the lug that went on the back of the bulb, connect the other two waterproof connectors, figure out that you can't fit the ballast when it's connected, disconnect it, fit it wherever it's going to go, reconnect it and it's done. It took me about half a hour to fit it to my GSX-R750, tucking the ballast inside the fairing on the right above the radiator and securing it with velcro and a cable tie for safety. It really is that easy, and the difference was staggering.

Now I love my GSX-R but the headlight isn't very good. I've tried everything but it still isn't up to the potential performance available. But it is now. The HID conversion is, I'd say, 200% brighter and, more to the point, gives a far more penetrating light that has allowed my speed outside the town to increase considerably while still keeping my margins up.

It's a simple fix, relatively inexpensive at around £110 for a single light conversion or £210 for both. And it works staggeringly well. Some bikes with better headlight designs will get even better results as the lamps themselves are supposed to be three times brighter than halogens. A useful bonus is that the lamp should last pretty well the lifetime of the bike, which is handy as bulbs get more and more of a pain to change.

So in conclusion, for the cost and the results, if you ride at night then this is a no brainer. Go for it and reap the benefit over the winter.

SB