Similar post:

http://www.bikeforums.net/electronic...l-luxos-u.html

You want the cutoff to be aimed more-or-less at a level horizon. I found a piece of level ground and aimed my "non-T" version of the lamp at a wall about 7-10 meters away so that the cutoff projected on the wall was about level with the actual lamp on the bike. Then tighten the mounting bolt so it's pretty tight but there is a little tiny bit of play left so you can ride a bit and adjust it if necessary, then finish tightening the bolt when you find the sweet spot.

You need to lift the front of the bike so the wheel is a couple inches/cm off the ground and spin the dynamo wheel by hand to activate the lamp.

It's normal to have a bit of wheel shadow if you mount the lamp on the fork crown. I had to modify the mounting bracket to fit under cantilever brakes so the wheel shadow extends about 5 feet/1.5 meters in front of the bike. Not a problem. It's unlikely that the wheel is obscuring the daytime running lights from the point-of-view of oncoming traffic. Unless, of course, the traffic is actually *in* the shadow of the wheel which is unlikely unless they're driving Matchbox cars.