Headlight beam aim

It's apparent from my first ride in the dark on the GSXR tonight that
the headlamp aim is a bit on the high side.

http://www.motuk.co.uk/mcmanual_160.htm suggests from the pictures
that the beam shouldn't be more than 850mm high using an aiming
screen. Which I obviously don't have, so I'll just stick a line on
the wall 850mm high.

Which raises the question; how far away does the bike need to be from
the wall?

 

Main or dipped beam?

Oddly, I have just had the lights on the MX5 re-aligned at an MoT place
round the corner. Long story, but in changing the bulbs I disturbed the
alignment. The owners manual sold me a dummy by not mentioning different
arrangements for models like mine with load levelling adjustment.

I got them roughly right using my garage door. For a car, about 10
metres with the centre of the pools of light on *main* beam at the same
height as the headlights.

Mine ended up a bit too low by this method apparently.

When I changed the headlight on the Voxan for a UK dip unit (off an MZ
Skorpion) I set the height off the bike by having the two units side by
side on a bench and powered by a battery. Just tweaked the new one until
it hit a wall at the same height as the original on dip, so distance
irrelevant. When it had its MoT and MSVA they said it was spot on.
--
+----------------------------------------------------------------+
| Pete Fisher at Home: |
| Voxan Roadster Gilera Nordwest * 2 Yamaha WR250Z |
| Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" |
+----------------------------------------------------------------+

 

Pointless anyway, as you'll generally find the MoT-approved headlamp
beam height is just a bit too low for real use. It's handy to know where
to set it for the test, though.

 

Far enough for the intended beam pattern to resolve itself is good
enough; usually a couple of dozen feet is plenty. If the dip's
more-or-less level with rider seated then it shouldn't make any
difference how far.

I actually rode the R1 in the dark for the second time today and I
reckon it's a bit marginal, though I have learned that Police cars,
with their highly-reflective tailgates, aren't good for judging
headlight aim. Or for making progress.

 

To the OP:-

No.
The 850mm bit refers to the two different possible
headlamp heights. Up to and including 850mm and
over 850mm.

In each case they must aim down a bit as follows:-

The best plan is probably to get the testing station
to adjust it to their satisfaction.

If you want to do it yourself then here are the numbers.
http://www.dvtani.gov.uk/uploads/customerservices/Headlampleaflet.pdf

One thing that is NOT mentioned is whether the vehicle is
to be loaded or not. In the case of a bike this could make
a BIG difference. Check with your test centre.
I would think that these numbers would be with rider
but that is a total guess.

The flat cutoff (on the right hand side) must be depressed
as follows:-:-

If the headlamp centres are 850mm or less from the ground
between 0.5 and 2 degrees down.

If the headlamp centres are more than 850mm from the ground
between 1.25 and 2.75 degrees down.


The "break point" where the elevated portion to the
left starts must be between straight ahead and
2 degrees to the left.

Need some trig.
Using google. Put the left hand expression into
google and we get the output given here.


To check we are on right track -
sin((90 / 90) * (pi / 2)) = 1
sin((45 / 90) * (pi / 2)) = 0.707106781
Looks good to me.

########################
# <=850mm height case #
########################

0.5 degrees
sin((0.5 / 90) * (pi / 2)) = 0.0087265355 - i.e 9mm per metre

2 degrees
sin((2 / 90) * (pi / 2)) = 0.0348994967 - i.e 35mm per metre

So for <= 850mm height every meter INCREASE in distance
from the target must cause the beam to drop by between 9mm and 35mm.

For 10 metres change of distance it would be 90mm to 350 mm.

Midpoint is 1.25 degrees.
sin((1.25 / 90) * (pi / 2)) = 0.021814885 - i.e 22mm per metre

########################
# > 850mm height case #
########################
1.25 degrees
sin((1.25 / 90) * (pi / 2)) = 0.021814885 - i.e 22mm per metre

2.75 degrees
sin((2.75 / 90) * (pi / 2)) = 0.0479781285 - i.e 48mm per metre

So for > 850mm height - every meter INCREASE in distance
from the target must cause the beam to drop by between 22mm and 48mm.

Midpoint is 2 degrees
sin((2 / 90) * (pi / 2)) = 0.0348994967 - i.e 35mm per metre



In decades gone past - the usual plan was for garages
to set it PLENTY low. As far as they were concerned
the lower the safer. (Safer in terms of possible
complaints). Most garages set the lights FAR too low.

 

On Wed, 12 Nov 2008 17:04:54 -0800 (PST), bod43 wibbled:

<snip>

It's really weird, but I was going to say exactly that.

 

(Deliberately left unsnipped)

Holy shitfire. I'm impressed (plus I have the nagging worry that you
might be conning us all).

PS: I just clout the top of my headlight wiv a fist.

 

That sounds reasonable.

 

Indeed, though it's more critical with bikes with long-travel bouncy
suspension than sprotsbikes.

My old XT600Z, at out-of-town cruise speed, would also pitch-up
slightly too, probably due to rider drag. I had to set the dip ever so
slightly lower as a result.

 

Our favourite tester *always* sits on the bike to check the beam
setting - as he's fairly recently qualified, I'd assume this is the
approved method. Makes sense to me, as it can't really be assessed on
the sidestand and the centre stand is out of the question - therefore,
the tester (or assistant) would have to hold the bike upright, and
might as well be sat on it. Sitting on it is the only way to obtain a
representative result, in any case.

Nidge never bothers, as he rides everywhere on main beam, of course.

 

is he dead, imprisoned, morphed or found somewhere else to spout bollocks?

 

Heh. I experienced his headlight first-hand at a bike show somewhere
between Stevenage & Bedford.