Daytime Visible Taillights
Very enjoyable forum here...lots of good info. Here's my two cents worth after spending the last year researching, designing, building, and testing daytime visible taillights.
Although pure power numbers are a big factor, they are not the whole story. Beam angle is also VERY important for daytime use. Other influencing factors obviously include flashing characteristics, inclement weather, solo or group use, etc.
Any of the low-cost options in the 1/2 to 2 watt range are generally perfectly adequate for night time use. PlanetBike obviously revolutionized this market with the introduction of the Superflash (followed by all the other similar variants). These are great lights for night use. Given their cost, anyone who EVER rides trafficked roads at night should have one or two of these at a minimum. One solid and one flashing. One of the tricks that these lights use to squeeze longer run times out of the batteries is a VERY short flash pulse of the main LED during a single flash cycle. Consequently, the distance between the viewer and this type of "burst" strobe can be a bit difficult to judge at night, which is why it's nice to have a steady burn light in tandem with the flashing.
Along comes the onslaught of low cost, higher performance Chinese lights (aka Magicshine). Their taillight is a bump up in brightness from the 2 watt devices and has a fairly decent beam pattern. Only the center LED is high power and provides any daytime usefulness. The mounting system leaves a LOT to be desired and the circular ring turn-on mechanism is finicky at best and destructive at worst. Mine was fairly stiff to turn and was actually turning the entire mechanism inside the housing and broke off the power wire from the circuit card, which subsequently shorted to the case and killed the battery pack... nice. But, if you can overcome all that, two of them in tandem would be marginally OK in the daytime.
Then of course there is the venerable Dinotte, quietly ruling over all other taillights with regard to sheer performance. Their 140 and 400R offerings (120 and 240 lumens, respectively) make fine daytime taillights and really should be considered the gold standard, by all counts. If cost is no object, (and how do you really put a cost on added safety) then these are the taillights for you. If you ever see a taillight out in the daytime that causes you to say, "WHAT in the world kind of taillight is THAT?" 99 times out of 100 it'll be a Dinotte.
Now, if cost is REALLY no object, and you want to make all your buddies with 400Rs have buyers' remorse, AND if you like going with a DIYer such as myself, then you could try the DS-500. All your perceptions of what an effective daytime taillight should look like will go right out the window when you see this much power (500 lumens). Of course, at that brightness level, you'll be relegated to the back of the pack, or you'll have to turn it down closer to the Dinotte levels. BUT if you're riding solo, this will cut through just about anything (rain, sunglasses, curvy roads, cell phones, etc.) and alert approaching motorists to your presence WELL before they get to you. Of course, I have to disclaim this shameless plug, since I'm the builder
, but finally, you can get some objective review from a "former" 400R user over at MTBR:
http://forums.mtbr.com/lights-night-...ow-726601.html