Bit Dim!!

[Gim]

Having decided hibernation is nearly over decided to try and rectify my crap headlight with a decent bulb only to find its already got one! But we also have a very nice shiny reflector positioned in front of said bulb. before I go mad with the tin snips and remove offending article any reason its there?
robin

[spacemonkey]

yes....from what I remember it's something to do with the light being all reflected on to the mirror so that all the available light is focused correctly, or something like that..
I have read a test of aftermarket 'performance' bulbs and the best by far were the standard replacement Phillips bulbs as found in Halfords. I have thought of changing to a 100/80W bulb but don'y know if the wiring could hack it.

[pooh]

The shiny bit in front of the builb forms the mask which stops your headlight shining on the wrong side of the road ie. why you have to change the light unit if you buy a continental spec bike. If you remove it the bike wont pass an MOT also you are likely to get stopped by PLOD.

Regards
Ian

[Will]

In order to produce a roughly parallel beam of light from the headlamp, the bulb is placed at the focus of an essentially parabolic reflector.
For this all to work properly you really want all the light from the bulb filament to firstly travel 'backwards' onto the reflector so that it can be 'focussed' into the correct beam shape - best not to remove that bit of metal otherwise you will produce a worse headlight beam.

It's a bit like the old mirror telescope working backwards.

Well thats my hypothesis - seem to remember something like this from Fizzicks lessons many years ago!

Will

[spacemonkey]

That's what I said... I guess we were both awake during the same lesson!

[ladybird]

i have a bulb to replace mine with and it has 'stuff' on the tip, does that mean i can take out the hat?

H4 Spectrum UltraWhite http://www.motorcycleworldl-spa.co.uk/images/uploads/Ultra_White_H1_and_H3_white.jpg

also, how the hell do i change the bulb, some ****er has nicked my manual that i had stored with my lube down by my bike

and will this one actually fit?

[Zimbo]

i have a bulb to replace mine with and it has 'stuff' on the tip, does that mean i can take out the hat?

H4 Spectrum UltraWhite http://www.motorcycleworldl-spa.co.uk/images/uploads/Ultra_White_H1_and_H3_white.jpg

also, how the hell do i change the bulb, some ****er has nicked my manual that i had stored with my lube down by my bike

and will this one actually fit?

No, and yes.
I'd buy the Philips Vision Plus instead though personally.
There's a lot more to decent light patterns than bulb colour or wattage, and accuracy of the filament placing is crucial for correct focus. The Philips tolerances are very tight and that's why they always win the group tests, Halfords premium bulbs also seem to do well. Cheap bulbs usually perform worse because of greater manufacturing tolerances and poor focus as a result.
Also, a note on blue / white light - it's great as a main beam as it projects really well, but it's crap in misty or foggy conditions because it just reflects back, yellow cuts through much better. The Philips Vision Plus bulb is dual colour, yellow tinted low beam and blue/white on main beam, so performs better as an all round bulb. Note the blue tint at the end of the glass.

http://www.oneshift.com/carprofile/images/part_full/593.jpg

[ladybird]

i see, might keep these as spares then and get some nicer ones (these were £9.99 for a pair)

still don't know how to fit the bugger though

[Zimbo]

It's very easy, simply undo the screw that holds the light rim on, pull off complete with reflector unit, remove plug from back of lamp, remove bulb (held on with a couple spring clips) and fit replacement, reassemble. five minute job. Make sure you don't touch the glass part of the bulb with yout skin, they run at v high temperatures and the oil from your hand does it no favours.
Philips Vision Plus or Halfords Premium bulbs are a tenner each.

[Will]

The headlamp reflector is a parabolic reflector; the bulb element is placed at the reflector's ''focus, the little reflector in front of the bulb is there to ensure that all of the light is sent back onto the main reflector surface so that the light is sent forwards as a roughly parallel beam.

Just noticed that I already said this stuff ages ago - DOH!

Try this: http://en.wikipedia.org/wiki/Parabolic_reflector

[JerryXt]

guys, I've got a 130/something if anyone wants it. Xenon gas thingy. I used the other on my Xt. Brilliant light :)