Citroen XM Forum

The problem with HID's is that they seem to need a different reflector / lens design to Halogen etc. Positioning of the HID units is very critical to get the right output without dazzling other road users. I have a Varadero 125 motorbike and several owners have upgraded them to HID, but it took lots of triel and error to get them set up right, and even then you need an understanding MOT tester to get them through.

LEDs are probably better then as they can come in the type that have the leds fitted all round the supply pole..

I have yet to see an after-market LED "conversion" lamp (even in single-beam H1) that can offer the brightness of a good halogen bulb (although I'm willing to be convinced).

The problem with the devices which consist of a central "pole" covered with LEDs is that they do not constitute a "point source of light", around which all halogen headlamp units are designed. By having a large/diffuse light source, the optics of the beam are poorly operated, and the result is a poorly focussed beam - i.e. scatter and increased dazzle. The other consequence is compromised illumation of the road surface, simply because the beam direction is poorly controlled.

It's all a matter of elementary physics/optics, as any A-level student would know!

Well I have a feeling there may be a development or change in this sometime soon

Hopefully, yes. Just looked at some Cree H1 units, and they are approaching a compact light source, but at $200 each...

There are some impressive single LED bike lights out there, some brighter than a modern car headlamp, but they're very expensive at (last I looked) a minimum of £200. While this is probably the current reason against their widespread use, I suspect a longer term one will be legislation.

As long as the beam is focused correctly a brighter light shouldn't be an issue.

And yes £200 May seem like a lot but then, comparing a candle to a nice bright light isn't that much in the scheme of things

At the end of the day guys..im just messing about with different looks Im not on a scientific mission to make xm headlamps any better or anything nor am i going to bother trying to convince others to do as i do.

Sometimes posts take on a life of their own and go in different directions to what they were intended

Don't expect the LEDs to change anything, it's not the question of being bright enough or not. Even if it were thrice as bright as the current halogens, there is absolutely no way a LED bulb can be fitted to a non-LED headlamp while retaining anything remotely similar in lighting pattern. It just won't happen because the necessary projecting surfaces around the bulbs are so dissimilar. Shops wanting to sell their bulbs will tell you otherwise but they lie. LEDs in other places around the car might be OK but not in headlamps.

It might still come but then, those LED bulbs will be something radically different from what we have today.

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Hi Vince

Sorry for the wanderings.
I will wipe any further headlight postings in your blog except yours and replies to your questions.
This evening I will try to find the time to start a separate XM headlight blog.
Then I will copy the headlight entries from here.

John