It's down to the position of the point light source being at the focus of the parabolic headlamp reflector. This is how H4 headlamps were designed. Nothing to do with the regs being out-of-date.
LEDs don't have a point light source, they have many sources and they're positioned to throw their light out differently directionally speaking then H4. (mainly sideways)
This is a good reference ... https://en.wikipedia.org/wiki/Parabolic_reflector#Applications
That's why the light pattern is wrong when using LEDs on older lamps, it's why you can dazzle other drivers. Physics.
1997 'K' series 1600 Seven Supersport (158bhp, Nitrons, SCS Delta ECU)
and some other toys...
Thanks for that. And I do understand the physics!
LEDs don't have a point light source
No, they don't, but neither do incandescent halogen bulbs. The H4 dipped-beam filament is typically about 5mm long, and the Dave Gemzoe dipped-beam LED cluster is about 7mm long:
For info, this is what my headlights look like (post #60).
Sorry, wasn't trying to teach you anything.
I have the Dave Gemzoe ones, but the MoT Centre still made me take them out (and I put them back of course).
I still have them in the drawer but for £100 the E-Marked LED complete ones seemed a good idea. And I have the DRL too.
I don't think it makes an iota of difference whether the lamps work like the old H4. The law is the law. Arguing with it won't work, even if you're right.
I was mightily aggrieved after my MoT, they lectured me on the fact that I was going to dazzle oncoming traffic. I complained that my alternative was possible death.
I even decided that, for what little night-driving I do, I would just use the H4 lamps the MoT Centre fitted for me, but they really are dreadful.
No need to apologize, Paul!
My DG bulbs were still in for the last MOT, and the tester didn't bat an eyelid. He was much more concerned about headlight alignment and possible dazzle. I did take along my old +130% Philips halogens just in case. If I have problems at future MOTs, I'll either revert to the halogens (which are pretty good, really) or bite the E-marked LED bullet. Or I might go for the +200% halogens I've just fitted to the tintop -- they're impressive.
I drive very little at night, but I do run with dipped beam all the time during the day. That was a big reason for going LED -- lower current draw. When abroad, I use tape to cut out the nearside beams, and lower current means less heat to damage the tape!
Agree that the law is the law, even though in this case it's also an ass.
As JV said, and in the same spirit
When I first purchased my LED bulbs I did my best to measure the position and size of the LED chips vs the coiled filaments in the Halogen - there was very little difference and neither are point sources - no coiled filament lamp can ever be. In fact, shrinking LED technology has reached the level where it can actually be nearer than a coiled filament to being a point source.
I agree that the law is the law, they are illegal etc. But I don't buy into the 'they are dangerous, the beam will be different, and you will dazzle everyone' claim.
I think I will have to either declare the modification to my insurer and ask them to maintain my insurance or go for E-marked units (and declare the modification to my insurer and ask them to maintain my insurance) as dim yellow halogens isn't an option.
I don't know what all the fuss is about. When I started driving the "standard" headlight was the 7" Lucas sealed beam. If you would like to try some for comparison I can let you have some then you will know how good the current halogens are
1985 S3 1700 XFlow. Undergoing full restoration
All very interesting ..... I've been pointing this out in relation to rear lights for years but again many members seem happy to fit aftermarket lights or LED upgrades without the correct approvals.
Can anyone clarify, is driving (day or night) with LED headlight bulbs actually illegal? They won't pass an MOT but that doesn't automatically make them illegal for road use, as far as I'm aware it's different legislation.
There's probably 100's of other examples where the same applies, driving with an empty washer bottle is not illegal, but it won't pass an MOT, carrying a bald spare tyre is not illegal, but it won't pass an MOT. Emissions legislation is the same.
Apologies if I missed it, but can anyone reference the appropriate legislation that outlaws LED bulbs fitted in E-marked H4 headlamp shells, other than MOT related?
Caterham and Lotus Seven Club Leadership Team Member
The register for all numbered limited-edition Caterhams ....... www.thecaterhamregister.net ...... www.instagram.com/thecaterhamregister
I have bought the same units as ACFowles.
Possibly a silly question but how should I get the sidelight function to work?
I am planning on snipping the wires to the existing sidelight unit and crimping spade connectors onto the black and red wires.
Based on ACFowles' previous post, am I correct in assuming that if I connect the red sidelight wire (which I believe is 12v) to the red wire on the LED unit the white ring will illuminate and function as my sidelight?
Is this legal?
Beginner with all of this electrical stuff so apologies if blindingly obvious!