Halogen headlights

Strider590

Joe_Horner wrote: »

That's not what you suggested. You suggested aligning them for MOT (-0.28 deg) on the first "dip" position of the adjuster, then moving them up by using the adjuster after the test. That will take them above the horizontal and dazzle people.

The reason for the -0.28 degree limit rather than horizontal, btw, is because roads aren't completely smooth. If you set them exactly horizontal then every bump will have them bouncing above horizontal and giving that really annoying flashing effect that we've all experienced as the cut-off jumps up and down into oncoming driver's eyes.

Seeing as the actual light output from low beam isn't much less than main beam (it's the aim that changes, the wattages are very similar), that gives the same effect to other drivers as driving towards them flashing your high beams on and off.

Which happens anyway, so what's the difference?

The reason it's set the way it is for MOT, is also to account for large/tall vehicles, which have headlights at a much higher level.
When you do consider differences in car height (both headlamps and windscreen), then this whole thing turns into an exercise in BS, a complete joke.

Retrogamer

I usually find the 35watt aftermarket HIDs less dazzling than the OEM HIDs fitted to most cars. Especially range rovers.

Joe_Horner

Strider590 wrote: »

Which happens anyway, so what's the difference?

The reason it's set the way it is for MOT, is also to account for large/tall vehicles, which have headlights at a much higher level.
When you do consider differences in car height (both headlamps and windscreen), then this whole thing turns into an exercise in BS, a complete joke.

No, large vehicles with higher headlights have an even lower limit ofr the beam cut-off (headlamps more than 85cm above ground level require a dip of 0.72 degrees instead of 0.28 degrees for lower lights). That's what accounts for higher lights.

The reason for the "below horizontal" requirement is that it makes flashing over bumps far less likely than horizontal.

If they're horizontal then the tiniest bump will move them above horizontal, and if they're above horizontal then they will go as high as oncoming drivers eyes at some distance. That's basic physics.

If they're below horizontal, even by a few tenths of a degree, then it'll take a progressively bigger bump to do that. Of course it'll still happen sometimes but it'll happen a LOT less.

Regardless of all that, your suggestion was to basically find a way round the required settings in order to have your low beam permanently above horizontal except when it's being tested.

That will dazzle others and will be very little different to failing to dip at all because the difference in power is typically only about 5 Watts. The only thing that stops low beam dazzling is the cut-off being below eye level - if you mess with that, you dazzle.

Strider590

Joe_Horner wrote: »

Regardless of all that, your suggestion was to basically find a way round the required settings in order to have your low beam permanently above horizontal except when it's being tested.

No, that's not what I suggested..... I suggested raising them by the value of one notch, this would be closer to horizontal, but not as you suggest "permanently above horizontal".

Joe_Horner

Strider590 wrote: »

No, that's not what I suggested..... I suggested raising them by the value of one notch, this would be closer to horizontal, but not as you suggest "permanently above horizontal".

Each "notch" on a headlight adjuster typically makes around 1 degree difference to the alignment (1.25 degrees on my Pug because I'm a sad git and measured it last night).

That means that, if you dip it by one notch on the adjuster (so "down" 1 degree), then set it to the MOT requirement of -0.28 degrees, then raise it again on the adjuster, it will end up at -0,28 + 1 = +0.72 degrees. That's 0.72 degrees above horizontal, and the top of the beam will rise above the horizontal by (tan 0.72) x 100 = 1.26 cm for ever metre it shines.

At 10 metres that puts it 12.6cm (about 5 inches) above the headlight level, at 20 metres it's 10 inches and at 50 metres away it's over 2 feet above "lights" level - easily high enough to be dazzling oncoming cars!.

And that's without considering the "bump flash" effect (nothing to do with pregnant chavs) which is annoying as soon as it goes above horizontal (exactly the same as pregnant chavs).

Strider590

Because you measured that on your car, it's the same on all?

And how exactly did you measure that? Because i've got a mechanical and a digital inclinometer, the only accurate way would be to use one of these on the headlamp unit itself.

Joe_Horner

Strider590 wrote: »

Because you measured that on your car, it's the same on all?

And how exactly did you measure that? Because i've got a mechanical and a digital inclinometer, the only accurate way would be to use one of these on the headlamp unit itself.

No, it won't be the same, which is why i said "around 1 degree" after measuring mine at 1.25 degrees (to the nearest 1/4 degree). They all have a similar effect, so they'll all be around the same.

As for measuring, it's really a very simple bit of geometry:

Put car on level ground facing a flat wall.

Shine low beam on wall.

Drive car carefully and straight up to the wall and mark the centre of the bright spot when the lights are virtually touching. That's the horizontal mark.

Back up in a straight line to a convenient distance.

Measure distance from front of lights to wall (in my case 4.6 metres)

Make sure adjuster is fully "raised" and mark position of cut-off

Dip by one click and mark new height of cut-off.

Measure vertical distance of each mark below the horizontal.


For each mark, calculate the angle of dip:

angle of dip = arctan (dip distance / distance from wall)

In my case the figures were:

distance from wall = 460cm
normal dip = 2.5cm below horizontal
adjuster dip = 12cm below horizontal

Normal dip angle = arctan (2.5/460) = 0.31 degrees
Adjusted dip = arctan (12/460) = 1.49 degrees.

Effect of adjuster = 1.18 degrees, or "about 1.25" to nearest 1/4 degree to allow for measurement errors.

All of the above takes about 5 minutes if, like me, you have a convenient wall that you already use for checking pre-MOT / after lights changes. If you have to drive round looking for a wall it might take a little longer. And who said geometry lessons would never be useful?







eta: Incidentally, even if the figures from mine aren't typical, it really doesn't matter. The highest allowed is 0.28 degrees below H so, even if a different adjuster only makes a tiny 0.29 degrees difference, that will still be above horizontal and cause the same problems.

Regardless of the actual figures involved, your suggestion means that you would be intentionally driving round all year with your lights set too high to pass an MOT and you would be dazzling people.

Double_V

You already have halogen bulbs.
What you need some new Xenon bulbs which are much brighter in terms of light and gives you that "whiteish" effect.

All new cars are either with xenons or hid installed.

Strider590

Joe_Horner wrote: »

Regardless of the actual figures involved, your suggestion means that you would be intentionally driving round all year with your lights set too high to pass an MOT and you would be dazzling people.

No, your just not getting it at all, or your being deliberately obtuse.

If a headlight on most cars has a soft cut off, for example an inch on your wall then one that has a very harsh cut off could be adjusted to cut nearer to the top of that point. It wouldn't be any more dazzling, it'll only fail an MOT because the centre of that cut off point will be too high compared to the centre of another headlight unit.

The entire purpose is to get the Vectra headlight to project as much light down the road as a car without these poorly designed projection headlamps. When you drive these cars at night, it is literally like wearing a pair of glasses with the top half of the lens painted black.

Some people like OP complain about them and try fitting fancy bulbs, only to find out it makes the situation worse, others seem to give up and just use the main beam regardless of oncoming traffic. I personally use standard cheap halogen bulbs, allow my eyes to adjust and avoid using my main beam, because once you use the main beam the dipped headlights seem 100x worse.