[roj1943]

Hi Rob
The short answer is that they are illegal in the UK unless fitted by the car's manufacturer complete with auto levelling and headlight washers. Auto levelling would not be an easy thing to do yourself unless you can find a specific kit made for the job. Effectively it does what the little manual headlamp levelling wheel does, but it needs level sensors and some electronics to make it work. Google HiD lights and you will find a lot of info.
Roger.

PS They get brighter 'cos they are arc lamps with a soft start.

 

[roj1943]

Hi Rob
I'm no expert, but I just Googled HID lights. Here's a quote:
"The HID bulb itself is similar in basic design to traditional HID lamps (a common example being the fluorescent tube used in interior lighting). Two electrodes are sealed in a quartz envelope along with a mix of solids, liquids, and gasses. When cold, these materials are in their native state (at room temperature) but are mostly gases when the lamp is hot. Starting of these lamps may require up to 20 KV to strike an arc but only 50 to 150 V to maintain it. Lamps may be designed to operate on either AC or DC current depending on various factors including the size and shape of the electrodes. A unique set of ballast operating parameters must be matched to each HID bulb.
Of all the problems that had to be addressed for HID headlights to become practical (aside from the cost), the most significant was the warm-up time which was solved by programming the controller to deliver constant power to the lamp rather than the more common nearly constant current that would be provided by a traditional ballast. With this twist along with a special lamp design, the lamp comes up to at least 75% of full intensity in under 2 seconds."

And another:
"Clearly, these lights can be fitted to any car but the law requires any such car to be fitted with either a headlamp beam adjuster or self-levelling suspension."

Just type "HID lights for car" into whatever search engine you use, and you will get more information than you could ever need.

Have fun
Roger.

 

[roj1943]

Hi Rob
I have had no experience with self levelling suspension or headlights, but a little thought leads me to make the following comments.

Cars with auto levelling suspension are not kept at right angles to the Earth's gravity which a gyroscope would do but simply kept parallel to the road. Imagine going up a very steep hill with a gyroscope controlling the level. The car's rear wheels would be several feet off the ground! Think about it!

All you would need to do to keep a car level, ie parallel to the road, is to measure the angle of some suitable suspension component. If you load the rear of a car (say) and the rear then dips, the suspension must have moved. Measure how much and use hydraulics to raise the suspension to suit. Self levelling headlights could, presumably, use a similar system.

I was not aware that X-trails had self levelling suspension so if that is what you have, I would appreciate some details so I can go to my dealer and ask why he didn't tell me so that I could have had one!

Roger