Taillights

This Sub-Page of http://bicyclelighting.com last updated on 20 March 2008


One of the biggest problems with commercial lighting systems is the inadequate tail lights. The best tail lights, in terms of visibility, are xenon strobe lights. These are finally being offered by Lightman, and are also being resold by Night-Sun (in fact xenon strobe tail lights are the only tail lights sold by Night-Sun). With a 12 volt system you can also use one of the many Xenon strobes available for automobile use; these are much less expensive, typically under $10. Xenon strobes are a far better choice than LED blinkers. Xenon strobes are much more visible, especially in areas that have a lot of ambient light. Xenon strobes are also very visible in the daytime, where most LED blinkers are worthless. In low visibility conditions, such as rain or fog, LED blinkers are useless, while xenon strobes will still be visible. Xenon strobes are much less directional, with visibility over an 180 degree range, while LED blinkers are limited to 50-60 degrees, except for a few with side pointing LEDs. I've seen concerns voiced that the xenon strobes are so bright that they annoy motorists, but in fifteen years of using them I have never known this to be the case (these strobes are not as bright as the strobes used on tow trucks or police cars).

So why are LED blinkers so popular if they are so much worse than xenon strobes? Amusingly, one cyclist in rec.bicycles.misc claimed that LED blinkers must be effective simply because so many people use them. The fact is that they are popular because they are cheap and widely available. Please don't fall for the "Everybody does it, so it must be safe" fallacy.

If you choose to use an LED blinker, go with one of the ones recommended below, the best choice is the Cateye LD1000. If you still choose to use a small LED blinker then also use some large red reflectors. In Effective Cycling (click to buy, but beware that some of the material is dated), John Forrester goes so far as saying that if you have adequate reflectors then LED blinkers are unnecessary. While in general Forrester's statement is true, there are cases where an LED blinker is better than reflectors-only; i.e. if a vehicle doesn't have its headlights on, a reflector doesn't work.

Note that flashing red lights (and flashing blue lights) are not legal for use on moving vehicles in many countries, and in most states in the U.S.. An LED blinker is not bright enough for the police to bother you (in most cases), but a red strobe may be a different story. If using a strobe, it is better to go with an amber strobe, since in most places these are legal for use on slow-moving vehicles.

There is an extensive U.K. study on beacons, entitled: Motor vehicle conspicuity: - Warning Beacons. It is very interesting to read the comparisons of detection times based on color. Amber had the poorest detection time based on constant intensity, but the best in real world because of the way strobes are manufactured (amber strobes of are higher intensity given a specific lamp intensity filtered by a colored dome because the amber domes transmit the most light (other than clear domes)). They conclude that amber and red strobes, together, offer the best compromise in detection and discomfort.

Xenon Strobe
The taillight I use is a Velleman xenon strobe tail light available from All Electronics (red, green, and blue also available); current draw is 1.8W. There are other 12 volt Xenon strobes available, including one that is re-sold by Nightsun.
There are now several commercial xenon strobes available, but you have to order them on-line as bicycle shops do not carry them. Blue strobes may not be legal to use as they are often restricted to law enforcement personnel. Red flashing lights are illegal for use on moving vehicles in most places, and this includes bicycles. Amber is the best choice, both for visibility and legality. Xenon strobes usually are sealed, with the bulbs soldered onto the printed circuit board. Replacement bulbs are sold at Radio Shack, but it's probably more trouble than it's worth for the Velleman strobe at only $9.

The flash frequency of xenon strobes decreases as the battery voltage falls. This is a problem on the AA powered xenon strobes. You always want to have good batteries in the strobe. The 12 volt strobe is a better option if you are running a 12 volt system.

A red taillight should always be used in conjunction with an amber strobe. This keeps you legal, and provides additional visibility. You can use an LED blinker, set to steady-on to be legal, but flashing is better).

Note that xenon strobes use a lot more power than LED flashers. The xenon strobes with internal batteries will run only a couple of hours. High-capacity rechargeable batteries should be used for xenon strobes that are heavily used, and carry some spare alkaline or lithium AA cells as a back-up.

Click Images for Details

Velleman HAA40
Amber Strobe

Variety of Colors

120 flashes per minute

Make your own mount.

Nightsun 12 volt Red Xenon strobe for civilian use (they will not sell the blue xenon strobe to civilians) Basic

Does not include Bicycle Mount

Basic Bike

Variety of Colors

Bike Commute*

Variety of Colors

*Night-Sun sells this for  $30, with a 12 volt, non-self-powered version for $40)

Professional

Variety of Colors

Sparky

Variety of Colors

Coghlan Strobe

Comes with clear, red, and amber lenses. Magnetic or belt mount so you'll need to figure out a way to attach it to your bicycle. Uses 4 AAA batteries

$9   $16 $25 $35 $50 $20 $11
12 Volt Xenon Strobes Self-Powered Xenon strobes

Taillight Mounting

Rear Rack
The Velleman strobe has two studs out the bottom and they include nuts and lock washers. I simply used a piece of flexible steel (from a hose clamp) and drilled two holes in it to match the studs (with a little extra length). I then clamped the strobe onto the back of the rear rack (a Specialized Expedition Rack). You could also use a short piece of steel banding from crates. Some rear racks Tubus Cargo Rack has a place to mount rear lights. You can also get a self-powered Xenon strobe. I don't think that blue is legal for non-law enforcement personnel. Note that most states require a red rear reflector but do not forbid the use of amber lights (which are more visible than flashing red lights); do not remove your red reflector if you choose an amber strobe. I find that amber strobes are better because to a motorist they denote caution, while a red strobe blends in with other red tail lights of cars. Check local laws.

You may want to consider using two xenon strobes, one in the center and one extending out to the left side (or one on the left side and one on the right side). Use a thin strip of wood to mount the strobes, and then fasten the strip of wood to your rack. The wood should be thin so it breaks if hit. 

Amber Strobe attached to Rear Rack. Use a short strip of flexible steel with holes drilled to match the studs. I had an old hose clamp that I grabbed. You can't use stiff aluminum bar because the studs aren't long enough. Use some Loctite on the nuts as well. Strain relief the thin wire that goes into the strobe with a cable tie to the rack. Battery goes into a rack top bag that I carry while commuting.

Reflector Bracket
Rear reflector brackets that mount to the rear brake bolt are fine, even the Dimension plastic one. This approach should only be used if you do not have a rear rack, since the rack, even without luggage, will block the light.

Click Images for Details

Dimension Rear Reflector Bracket. $2.95 from bikeman.com.

Seat Post or Seat
Mounting a strobe to the seat post can be accomplished with a seat post bracket. Note the swivel so you can make the light straight even though the seat post is slanted--be sure to adjust the bracket so the light is level. Measure the diameter of your seat post with a vernier caliper and order the proper size bracket.

Click Images for Details

Cygo Lite Seat post Light Bracket Fits 25.4-27.2mm

Cygolite Seat Post Bracket Fits 25.4-27.2mm seat posts. $2. Dimension Seat Post Bracket RF1009 Fits 28.6-31.8 mm seat posts. $3.95 Dimension Seat Post Bracket RF1008 Fits 26.8-27.4 mm seat posts. $3.95 This bicycle has a reflector bracket attached to the seat post. Sorry for the nudity, but it was the only picture I could find of a bicycle with this type of reflector bracket (I guess not many people want to take pictures of just reflector brackets). Close-up of reflector bracket attached to seat post. Note that this reflector bracket is incorrectly adjusted, as it should be level. Sometimes the seat is so low that there isn't enough seat post left to have space for a reflector bracket. This bicycle is really too large for the woman that is riding it. Again, sorry for the nudity, but no one goes around taking photographs of just seat posts! Be certain to aim your LED flasher properly. This woman has her flasher pointing toward the ground where it does little good.

Rear Racks with Integral Reflector/Light Brackets
If you're buying a new rear rack you should try to buy one that has an integral mount for a reflector/rear light. The steel racks are nice, but very expensive.

Click Images for Details

Axiom Odyssee Tubular Alloy Rack with reflector/rear light bracket

Tubus CroMo Steel Rack Nitto Steel Rear Rack

$23

$100

$135


LED Blinkers
LED blinkers became popular because they are cheap, widely available and because the batteries last a long time. LED blinkers are often the only type of tail lights sold at bicycle shops, web retailers, and hardware stores, which leads to their popularity. So since everyone seems to use them this must mean that they are good, right? Well, no, not really. Here is a list of some of the problems with LED blinkers.

  1. They are not very bright. They look great when it's really dark with no other light sources from vehicles, street lights, etc., but in reality they do little to make a cyclist visible in traffic. 

  2. They have a limited visibility range (50-60 degrees) compared with 180 degrees for xenon strobes. 

  3. They are virtually worthless in rain, fog, or other low visibility conditions.

  4. The cheaper ones have no reflective material behind the red lens; unfortunately you will be unable to determine this until you open the package and inspect the unit.

  5. They are usually not built very well. They are not waterproof, the snap on lenses can pop off when you hit a bump, and the mounting to the bicycle is usually by a cheap plastic clamp.

  6. They are not visible in daylight (a xenon strobe is visible even in the daytime).

  7. They are small, and to a driver small means far away (note that this does not apply to the 4"x6" LED flashers)

  8. They are red, which is a less visible color, especially to older drivers. Yellow is a better color for a flasher because it is more visible to the eye.

  9. They need to be carefully positioned in order to be visible. This is due to their limited visibility range.

  10. They do not emit enough light to be useful at all on winding roads. With a xenon strobe, a motorist coming around a curve will have an earlier warning.

  11. In most states, flashing red lights are not permitted on moving vehicles, but flashing amber lights are okay.

In areas where flashing lights are illegal, high brightness LEDs may be a viable alternative to a strobe (in most of Europe, blinking lights are illegal and the LEDs stay on all the time). 18 high brightness LEDs will draw 360 mA or so when on all the time, and maybe 100 mA when flashing, a Xenon strobe will draw 150mA max.

In short, I am very much in favor of spending the money for xenon strobes because they are far more effective. Even Night-Sun, the premier high performance bicycle light company, sells only xenon strobes for tail lights.

Also read "http://www.gonecycling.com/commuter/commuting.html" which states: "Certainly the most common type is the LED flashing rear light. Be aware that the devices are very directional. Unless a motorist is directly and level behind you, and you aimed it right, the effect is not much better than a reflector of the same size... Reflectors work great at the back of the bicycle. I use a three inch amber reflector on the fender and it works great. I'm sure it is the first thing a motorist will see on a flat level section. For illumination, I used a Xenon strobe. It is much less directional than LED and brighter too. More expensive and the batteries last only two winter commutes."

There are (or were) some decent LED blinkers. One is called Real Lite, and it is available from Harris Cyclery. It is quite costly at $40. If Sheldon Brown endorses it then that's good enough for me! I received an e-mail from the importer of the Real Lite that stated that the Real Lite uses high-brightness LEDs while the cheaper 18 LED blinkers do not. This is part of the reason for the disparity in price; the high brightness LEDs are much more expensive. The Real Lite LEDs will have a longer lifetime than a xenon strobe.

The Specialized Afterburner Comp has a unique lens system that appears to somewhat solve the viewing angle problem. Unfortunately it has been discontinued. The big complaint about this light is the poor mounting bracket, so you'll have to figure out a way to mount it. Martin Kreig of the National Bicycle Greenway, wrote: “I've been lusting for the perfect bike flasher since the days of the trusty Belt Beacon.

The Trek webpage at http://www.trekbikes.com/accessories/cat_browse.jsp?category_id=130 states that Trek offers tail lights with up to 330 degrees of visibility, and up to 5000 feet. Trek has removed this light from their web page, so I thought they have discontinued it, but according to a local Trek dealer in my area, it actually is available: "TREK part# 69575, Disco Inferno flashing tail-light, presently available in large qtys at both east & west-coast warehouses (midwest warehouse presently out of stock). This light has not to my knowledge been discontinued and, in fact, has been recently revised. Price is about $25. Impressive light; I've installed one on my rain bike."

Click Images for Details

Real Lite 18 LED Tail Light. Uses 4AA Batteries. Specialized Afterburner Comp (discontinued) Trek Disco Inferno (red version is discontinued, but a white version is still being sold at bike shops)
$40 $20 $28

There are six other available good rear lights.

First there is the B&M 4DToplight Senso, available in three different versions. The 4DT is not a flasher, but it does offer the wide angle of visibility. One good thing about these B&M rear lights is that they are available both in battery powered, and dynamo powered/battery backed up, versions; this means that dynamo aficionados finally have a decent rear lamp available. As far as I can tell, they are sold only by Harris Cyclery (Sheldon Brown), though one version is sold by Peter White Cycles.

Click over to: http://sheldonbrown.com/harris/lighting/shimano.html and search for "Taillights for rack mounting" and scroll down to the 4D series. There are three versions available:

1. 4DToplight Senso, (battery powered, switches on by itself in the dark): $ 26.95
2. 4DToplight Senso Multi, (generator or battery powered, switches on by itself in the dark): $ 29.95
3. 4DToplight Permanent, (battery powered only, doesn't turn on by itself): $ 21.95

 At least in the U.S., the 4DT should be used in conjunction with a Real Lite 18 LED flasher, since a flashing rear light has become the de-facto identifier of bicycles.

Second there is the Cat Eye LD1000 with six rear facing LEDs, and two sideways facing LEDs on each side. This is battery powered (2 AA) only. Quite pricey at $30, but there is no real competition. Click over to: http://www.nashbar.com/profile.cfm?category=101&subcategory=1068&brand=&sku=12860&storetype=&estoreid=&pagename=

Third, there is the Mega Bike Strobe tail light. This one is similar to the Real Lite, above, but has 17 LEDs rather than 18, with 15 LEDs pointed toward the rear, and two LEDs pointed to the side. Not sure about the brightness of each individual LED.

Fourth, there is the newly introduced Blackburn Mars 3.0 Rear Light with side LEDs. See it at http://www.blackburndesign.com/lights.html. Buy it at http://www.campmor.com/webapp/wcs/stores/servlet/ProductDisplay?partNumber=54722. This is a good deal at only $13, not much more than a junky LED rear light.

Fifth and Sixth. aret the Trek Flare 10 and Trek Flare 7. The Flare 10 uses 10 LEDs and provides (according to the manufacturer) 360 degrees of visibility using 2 AA batteries. The Trek Flare 7 uses 7 LEDs and provides (according to the manufacturer) 270 degrees of visibility using 2 AAA batteries.

B&M Senso Multi Cat Eye LD1000 Mega Bike Strobe Blackburn Mars 3.0 Trek Flare 10 Trek Flare 7
$22-30 $30 $18 $13 $25 $30

While it's great that there are some decent rear LED lights available, xenon strobes remain the best option for a rear light in a 12 volt system. This is due to their much greater brightness, wide angle of visibility, and significantly lower cost. However you do have the overhead of the separate battery.


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