# Bike lights with beam cut-off to avoid dazzling drivers?

Are there any bike headlights available that have a cut-off similar to a car's low beams, designed to avoid glare for other drivers? I am using the Light in Motion Urban 400 and while it's plenty bright, it blinds oncoming drivers if aimed normally. In traffic I have to aim the hotspot very low, basically defeating the purpose of having a pricy, bright LED light.

Are there modifications that can be done to the existing light, like blocking part of the reflector that is responsible for sending light upwards? (It's a single LED with a simple paraboloid reflector) Reading about the complexity of the design and regulations for car headlights, this seems unlikely, but I'd love to be wrong.

Alternatively, I am looking for recommendations for a better headlight. The Specialized Flux and the older Phillips SafeRide 80 seem to fit the bill. Not sure how bright the Phillips is with 220 lumens, but it meets German regulations so surely it has a great beam shape.

## locked by jimchristie♦Mar 15 at 19:58

This question exists because it has historical significance, but it is not considered a good, on-topic question for this site so please do not use it as evidence that you can ask similar questions here. This question and its answers are frozen and cannot be changed. See the help center for guidance on writing a good question.

• This design feature usually comes from the mirror and orientation of the LED, so it's hard to imagine meaningfully retrofitting a light. In particular, Busch & Muller lights are very good with this: peterwhitecycles.com/b&m-hl.asp – Paul H Jan 26 '15 at 18:42
• @PaulH many of the lights designed for european city bikes are. Commuting using the bike infrastructure round here would need one of those plus something designed for trails - poor quality tarmac and no lights at all, plus near-invisible hazards (dogs, some cyclists). – Chris H Jan 26 '15 at 19:57
• You could try designing a mount that makes it lower (like if your fork has low rider rack mounts or a front rack, mount it on that). – Batman Jan 26 '15 at 20:40
• Honest question - doesn't aiming the light at motorists increase visibility? – Trevor Jan 27 '15 at 22:17
• @Trevor It says there's something there, from miles away. It doesn't say where "there" is or what "something" is. If you've ever come had someone with a road-illuminating light come towards you on a bike path, with it pointing in your eyes, you'll know what I mean - you don't know whether they're on the middle of the path, or which side. I've also been so dazzled ended up stopping until I could see again after they'd passed. – Chris H Oct 3 '16 at 13:22

I have actually dramatically improved the cutoff on my 1200 lumen dual LED (just for reference) with a sort of brim made out of aluminium plate. On road I run it on minimum brightness (guessing about 1/4 -- 1/3 power). On pitch dark bike paths I do change the angle a little as well as turning up the brightness.

Super-speedy sketch (go inkscape!):

The light body is about 60mm long, and the reflector is in approximately the right proportions. I mocked it up with cardboard first, before using some 1mm plate - it's tucked away under the bars, under a front bag mount and all edge and corners are nicely rounded off.

The mounting underneath the handlebar is another issue -- overly reflective silver-grey brake and gear cables right in front of the light if it sat on top of the bars.

It's not quite as good as it was before I tweaked the handlebar angle. On (slight) riser bars using the riser as intended I had it tipped up on the left to illuminate roadside signs (UK). I've twisted the bars so the rise points forwards at about 45° and the aim isn't quite what I'd like.

I promised pictures:

Side view

Front view

Illumination pattern (high ambient light levels)

• Thanks, that's something I have been contemplating and this response has given me the nudge to actually give it a try. I think this has two drawbacks: One, total darkness above the cut-off, so it will be harder to see reflective traffic signs. Second, the cutoff won't be very sharp, looking into the light "almost" straight on, you gradually see more glare from the light source. I will try it out on my commute tonight and give feedback how it works. – Urs Jan 27 '15 at 1:59
• I considered using the lens from an old pair of sunglasses warmed enough to make it flexible. With a narrower light i would have done but it just didn't fit. That would allow around 40% brightness above the cutoff. But in practice the intensity didn't fall sharply to 0. – Chris H Jan 27 '15 at 17:06
• I accepted this answer because it does address the question, but to be honest it's not a good solution. It's just not possible / practical to get a remotely sharp cut-off this way without having the shade mounted absurdly far away (think carrot on a stick). My original idea of blocking parts of the reflector also does not work, turns out because the LED die is so big all parts of the reflector contribute the same beam shape. I endend up ordering a Phillips SafeLight 80, and I will delegate the Light&Motion to off-road use. – Urs Jan 28 '15 at 2:18
• On balance you're right. It does heavily depend on riding conditions and I definitely wanted a solution that didn't mean fitting 2 lights just for a commute (any decent lights needed to be removed or they would be stolen). The contribution to different parts of the beam isn't equal across the reflector on the one I have (a much smaller reflector than my previous light) so maybe that helps. – Chris H Jan 28 '15 at 9:33
• @ChrisH. Glad I upvoted you then! :) – James Bradbury Oct 4 '16 at 13:24

In Germany, all bicycle lights above a certain lumen value have to have a low beam feature, so it's pretty standard here.

So, if you do not want to kludge your existing headlight get a german one, e.G. Busch und Mueller Headlights always have a low beam feature, which they especially advertise.

Here is their english web page.

http://en.bumm.de/

• Thanks, I think there is no way around a light with a properly designed reflector. Strange they aren't really advertised, the LBS (Mikes Bikes here in California) only carries lights with symmetrical beams, at all price points. I ended up ordering a Philips SafeRide 80, with a similar "low beam" like reflector. – Urs Jan 28 '15 at 2:23
• The link has died. – Sparhawk Apr 4 '17 at 1:08
• I think it's worth to add these two points: 1) Beam cutoff is worthless if the light is misadjusted. 99% of the lights I see on other peoples bicycles either look at the ground in shame, or try to brighten the moon. And 2) it's far easier for dynamo power lights to stay adjusted. A click-on light with a battery needs to be taken off and reattached every time you use it, so you apply rather strong forces to it and the shoe that fixes it to the handlebar. Not so the dynamo powered light: You adjust it once, and as long as it stays untouched, it stays adjusted. – cmaster Feb 2 at 23:04

Lights that are road-legal in Germany have this cut off. The Trelock LS 950 is a good example.

I use Busch and Mueller Ixon IQ Speed - very pronounced cut-off at top. These have a low-light mode - good for street-lamp-lit roads as well as a very high-level mode which is great for unlit roads.

Yes they definitely exist - but control of the beam may be done in several different ways.

1. Mechanical interruptor to cut the beam's upper edge and make it a harder edge.
2. Well shaped reflector
3. Two separate LEDs with constructed optics to control the beam pattern.

I have two lights which are 2 and 3.

Type 2

This is a 375L lifeline front light that is no longer available. But the shape and angles of the reflector throw light down far more than upward.

(TBC) needs a better photo.

Type 3

Also own a Ravemen PR1200 light which has two modes each with multiple brightnesses. Runtime is from 2 hours at 1200L all the way up to 21 hours at 100L.

But the unit has two front LEDs, one that runs for all modes and one that only runs in off-road mode.

Manufacturer's images:

Ths is the low-beam mode.

And this is the high beam mode.

It has a remote button which is kinda nice but turned out to be quite flimsy wire. It also has a ~5Ah USB Power bank function, but the unit cannot charge a thing and also run the light, so its not that useful.

As a light, its really good, totally worth the price.

One last manufacturer photo, showing beam pattern from behind.

I found a ZHISHUNJIA DG666 on Deal Extreme with both a cutoff beam and a user replaceable 18650 battery that lets me carry a spare battery so that I don't have to ride home in the dark if I forget to charge the light. The other reason that I wanted a user-replaceable battery is that I hate replacing lights because the sealed battery has failed.

My tail light is a rechargeable LED road flare with a user replaceable RCR123 battery fastened to a velcro water bottle bracket for the same reason. I stole the idea from another rider after noticing that his light was visible from both the back and the side. I can also use a low power setting while riding in a group so that I don't blind the rider behind me.

• Very bright, very cheap, the product description is full of typos ("gree" for green, "cut-foo" for who-knows-what), and half the photos in the description are of a completely different product. I'm not sure I believe this meets the standards it claims to meet. – David Richerby Feb 3 at 17:40