I recently went to a dynamo system and am looking for advice on properly aiming the beam. I have the B&M Luxos B. These light have a fairly sharp horizontal cutoff - about how far away do I want to aim cut-off this for optimal lighting but yet not annoy motorists and pedestrians?

Right now I think it's a little low since the cut-off precludes seeing stuff 100+ feet away, whereas my old battery light was rounder and I had more early warning.

When cars start flashing their lights at you, you know your frontlight is aiming too high.

However, I reckon there simply are several variables at play here. What is your speed -- how far do you need to see in front of you? How is the road? What is the weather? I.E. is there ice or snow on the road, are there potholes you need to avoid?

Sometimes you just need to adjust the light during the ride several times to make it fit its purpose.

I have been known to point my B&M Cyos rather high, because road signs would light up ever so nicely then. Judging by the reactions of the cars coming towards me that was too high.

Find a very flat stretch of street with little or no traffic at night. Have someone stand in front of the bike. Ride the bike so the standlight is charged first.

You basically want the light lighting up their waist, but not their face. If their face is illuminated by the light, it's to high. You want it just below where it would hit someone in the face.

P.S. I guess for my test you'd want to find someone short, like 5"4. Basically for regular people you want the light hitting their waist but not above that.

If it's too low, you can see the cutoff on the street in front of you (assuming a level street!).

Just rotate it up until you don't see the cutoff.

Wow, lots of interesting techniques!

I think the aim point (height of the cutoff at a distance) should not be above the height of the headlight itself. If the headlamp is at axle height and you adjust it for waist at 50 yards, it will be in the eyes of anyone more than 50 yards away. If you mount it at 30inches height and adjust it for 29 inches height at 10 yards, then it will never be in anyone's eyes and will be at a height of 25 inches at 50 yards.

I prefer the second approach, but I don't know if my Luxos B has enough vertical spill to see street and speed limit signs.

FWIW, the European automotive headlight spec used to say the kink point of the headlight beam should hit the ground at 65 meters distance from the front of a car. The automobile headlight pattern has a kick-up on the curb side of the road, enabling (well, somewhat) seeing signs.

I mounted my Luxos U on the fork crown and used the wall in front of the tire to aim the light just a bit above the tire. Works fine for me, but I plan on asking my brother to sit in his car on a level street about 50 feet away from me and see how high i can aim before it bothers him, to get it perfect. I have looked into the Luxos light beam and its not as bright or bothersome as those bloody torches from Majicshine and alike. They are good for singletracks, or empty mups, but during rush hour evenings, they blind everyone. Be safe and just ride.

reflective signs light up further ahead than the light bathes the road.
if you feel a need to light 100 feet ahead , then turn it up, a bit,

you can augment the broad flood beam with a narrow spot second light

those are much easier to make and so more common..

the 'my lumens are more than yours' guys get lots of those .

Fair enough, the main point is that you can see where the light is hitting by seeing what it's lighting up. If if it lights up people's faces, then it's hitting them in the face and it's to high. If it's not lighting up people's faces (at any distance), then it's fine.

Thanks for all the tips everyone - this is very helpful. I aimed it higher for today's ride and could see farther ahead but don't think I was blinding anyone.

I always wondered what that was, thanks for mentioning it

I completely agree. And in order not to ever light up a person's face, the cutoff plane of the light must always point downward by some angle. That is the point I was trying to make with my less than clear writing.