What bike headlights have the longest beams? I guess the brightest light doesn't necessarily have the longest beam, but the ones with long beams are some of the brightest?

I think long beam may be as important as being bright, esp. at intersections, or next to big vehicles with blind spots. Also if you happened to be without a taillight, the long beam of the headlight can help with visibility all around.

(Gets Popcorn) lol...

The light I've used that goes the furthest down the road in my experience owning several lights is the Philips Saferide v2. Unfortunately, as soon as they made nice lights, they left the business and they no longer make lights. :-)

Another poster thought it was the Fenix BT20 in their experience, but I have not used that light.

In the last year - not sure if just noticing or eyes getting old - that the kind of color the light puts out makes a pretty huge difference. A lot of lights put out harsh light that's hard to see outside of the beam with. My Saferide v2 (and my Light and Motion Taz to a lesser extent) put out a nicer light output that lets me see outside of the main beam a lot better, as well as seeing inside the beam better as well. Hotspots in the beam can be pretty terrible in keeping you from seeing further down the road to.

Well, the headlight with the longest beam would be a laser, but that wouldn't be particularly useful. There are lots of threads in this forum about shaped beams. These lights have reflectors that focus the light to the area of the road where it is useful. Unfortunately these lights are fairly pricey. What you are asking for is a light that has a lot of throw. A light with a very wide beam (think light bulb) would be considered floody. What you want is a light with good throw and a decent amount of spill. I am sure there are industry standards for beam width measurements, spot definition, etc. Here is a glossary that might help you understand some of the properties of light beams. A glossary of lighting terms, from CertoLUX - Manufacturer of Specialty Luminaires for Medical Facilities, Vandal Resistant Applications, and Clean Rooms.

What kind of riding are you doing? Mountain biking or road? Total darkness or with street lighting? What is your price range? How long is your ride? Answering these questions will yield the most helpful responses.

Some of the Chinese CREE based lights are VERY BRIGHT, and relatively cheap.

Personally I prefer a bit of a wide angle beam rather than a straight spot ahead beam.

However, the problem with the cheap Chinese lights is that when you point the light at the horizon, it illuminates as much above the horizon as below, and ends up being extremely bright in the eyes of oncoming traffic, or other trail users.

The Specialized Flux Expert (and maybe other Specialized Flux lights) are designed to cut off somewhere below eye level, which also means the maximum amount of light is projected onto the road. A bit expensive, but it may be worth it.

See review:
REVIEW: Specialized Flux Expert Bicycle Headlight - Photo Intensive

Unfortunately they're a bit expensive

I would not want the light with the longest beam, because that would indicate that the beam shaping was horrible for being a road light. I don't really give a damn about lighting up a 20 foot diameter spot 200 feet up the road.

What I want is a properly shaped beam that lights up the entire lane from my front wheel to maybe 75 feet in front of me, with special emphasis on the 30 feet in front of me.

As for having a rear light out, IMO nobody should be relying on a single rear light, because they can fail and you won't know it. I always run two rears.

Ok I sounded extreme in saying 'longest beam'. I meant among the bright, good quality bike headlights that you know of, which have relatively longer beam. So hope that sounds more reasonable now. I'd be interested in comparison to the so-called MagicShine clone, the Chinese-made $20 CREE headlight that many are familiar with, 'cause that's the one I usually use and the beam is not too bad when on high.

Any light will travel an infinite distance if it isn't absorbed by anything, and in the far field, all light intensity decreases as the square of the distance. ( What's the far field? In a logically circular definition, it's the area in which the light intensity starts decreasing by the square of the distance.) This is as true for lasers as for any other light source. In looking for a light with the greatest "reach" what you are looking for is a light with the highest candela rating.

is use a Convoy C8 I got from Mountain Electronics and it throws farther than my magicshine. The C8 is a great light.

It all depends on the speed.

10 MPH = 15 feet per second
20 MPH = 29 feet per second
30 MPH = 44 feet per second.

So, coming down a hill, 75 feet may give you less than 2 seconds of visibility ahead.

I tried an emergency stop on the level from 30 MPH a while ago. I think it took over 30 feet to stop. That would be even further on a steep hill. So, you're suddenly into sub-second reaction time for a possible obstruction requiring a full stop. Plenty of time if you're at 100% concentration with both hands on the brakes.

I was running two Cateye EL650s on a T-bar aimed "well out" but still capable of lighting gravel/obstacles. Two on the handle bar with one relatively close and the other in the mid-range. Four lights worked pretty well for me cruising 12-17 on flat ground even without a moon for light. However, they EL650s are dying and I cannot find a "doubleA" replacement. I don't want a usb or weird battery light. I do want multiples because of the safety in redundancy. I make sure that the batteries are staggered so that no more than two lights can run down during a single ride.

I second the C8. I upgraded to a $30 XinTD V5 from Mountain Electronics and it is just a tad longer than the C8 I had been using and was a just enough brighter that I felt I had adequate light to be going 20+ mph. The key is to keep the light aimed at the proper angle to light up a spot on the road instead of aiming higher where it can blind drivers.

But it's not like you get good light out to 75 feet and then nothing beyond that. My experience has been that when the road is lit up nice and uniformly in front of me, there is still enough light to give plenty of warning for anything further out that is big enough to matter. This would be with a 400 - 500 lumen unshaped beam that projects reasonably uniform light. I generally try not to exceed the low 20 mph range when there isn't a decent amount of ambient light.

A few trips this summer with a full moon, I decided to go by clearance lights only. But, there are days when it is just plain dark. Those little silicone frog lights don't do much for lighting up the road.

I've got to ride my brakes pretty heavily on my driveway to keep it below 30. I did almost fill my freezer with Venison coming down the driveway a while ago

But, there are hills that I regularly hit. Most of them seem to have a natural speed in the low to mid 20's.

Cars usually have lights and reflectors. But there are other obstructions. It is easy to come up on pedestrians too fast. And, I've been on bike paths where I'll point my light downward when I see one pedestrian, and miss the next one. I suppose that would be a huge benefit for shaped beam lights.

I have found, by intelligent reflector design, the B&M IQ 2 beam has the most Practical beam for Riding a Bicycle ..

A Narrow Spot pattern would concentrate the light in a narrow focus , but that wont help you see the Pothole, right in front of You.

As most of you know - typically vehicle lighting needs produce lights that need to compromise between "flood" and "spot" patterns. And typically this means that "flashlights" always have tighter "spot" patterns than "made for bike" lights.

My own experience suggests that a good multi-cell 800 lumen flash light is effective when mounted in a manner that afford me the ability to point it into the eyes of oncoming motorists that fail to dim their own "ffff-iinng head light."

Other than that - I don't see much need for spot lighting........ Well - maybe on a high speed descent...... blah blah blah ....

European-designed lights have the best beam shaping. Lights are required on new bikes by Euro law (like reflectors are here) and must meet certain standards, so the Euros spend a lot of effort to design bright lights with excellent optics.

It gets confusing when lights are rated by different standards; in the US it is common to use Lumens, whereas the Euros use Lux (because that's how the Euro standards are measured). Lux takes beam optics into account, and measures an amount of light that actually reaches a target, not just the amount of light that the light emits (Lumens). There is no easy conversion, because to measure Lux takes an additional, real-world test.

So, most US headlights have a round lens with no beam cut-off. This results in a oval-shaped pool of light that, when aimed at a good attitude to illuminate your path, also shines a lot of light into the eyes of oncoming riders and drivers. You could argue that the "light in the eyes" makes you more obvious to traffic, but it may also dazzle them and make it hard to see exactly where you're located.

Most Euro headlights have a faceted lens with defined beam cut-off. This results in a rectangular beam that illuminates even more of your path without blinding oncoming traffic.

I recently upgraded to a dynamo setup with a B&M Luxos U. The beam is shaped well so I can illuminate the path 100 feet in front of me while not blinding oncoming riders. The beam is about 10-15 feet wide for most of that throw, so the entire path/lane is lit instead of a small pool from a non-shaped beam. The light is crazy bright; I've experienced a huge increase of how many cars see me and yield, and how much further away they do it. I have my light mounted up on my handlebars, so maybe they think I'm a motorcycle?

I've also purchased battery headlights (Sigma Sports) from Europe that had nice beam shaping but lower power.

Thanks for all the info. I saw some flashlights online with "C8" but without "Convoy", are they clones of the Convoy C8 some of you mentioned? Like this one?

And btw, according to my experience, long beamed bright headlights are m more effective than bells/horns in alerting pedestrians. They usually thought it's a car coming at them, so they jump to the side quickly (while the message sent by a bell ring is, it's just a bike, no worry)

XinTD C8 V5 XM-L2 U2 3C 18650 Flashlight is the one that a1penguin and I have, or the current model for mine. It comes in a couple of minor variations, but mines the best light I've ever used.

What's really needed for a light depends on where you need it.

As someone who rides including commuting and drives as needed there's a few things learned. Ive used a flashlight and the magicshine clone. Didn't think anything of it till the first time I came up on clown on a bike that felt the need to have one pointed straight head of him, while I was driving. Couldn't see crap. I proceeded to stop and politely explained why he needed to point it downward, I got the third degree about how he felt he needed to see so far ahead and so cars can see him. So I convinced him (didn't take much when I had my bike on the back of my car) to unstrap his light and walk up the lane , id walk the other direction with his light.

Got 150-200ft apart and I turned it on high and pointed it straight in his face.

When I saw him coming (though I always pointed mine downward) I decided I was switching lights cause I didn't want to get hit. When I did that to him and he was seeing stars for 5 minutes, he apologized, didn't realize it was that blinding at that distance when its pitch black out. We had a good laugh and he always pointed his light down till he got to the bike path.

Moral of the story, stop with the "flashlights" trying to see how far ahead you can light up, it just isn't needed. Either slow down or at least turn it down, point it downwards when you have oncoming cars/bikes. They need to be able to see too. Or get lights that use optics so the spot isn't so retina burning bright even on the mid lvl setting.

Nice anecdote (if only all drivers and cyclists could be so friendly to each other).

I ride on city streets and very rarely have the light on high (either headlight or taillight), for the purpose of saving battery charge. And I point headlight downward, never toward drivers' eyes. Since you have used both flashlight and the Magicshine clone, how does one compare to the other? Do you think the MagicShine clone's beam is pretty decent? I may try to get a C8 flashlight mentioned above to compare (thanks to everyone).

P.S. a question about battery chargers:
For charging one single 18650 battery, will there be harm/danger to use a charger that can charge more than 1 batteries simultaneously? e.g. using a dual charger to charge just one battery, would the other, empty slot be a accident hazard? (IOW should I get a singer charger for the C8 flashlight, or it doesn't matter if using a, say chargers for 4 batteries to charge 1 battery?). Thanks in advance.