BTW, somebody in this thread mentioned a bike helmet, I use a BD Icon for bike commuting and with the BD at it's largest setting, it fits over my helmet (a Bell something or other). What I do is I snake the center strap through the top of helmet via the vent holes and then I use zip ties (maybe one per side) to keep the side straps from slipping off. The side straps will tend to want to slip off. I use the highest settings on the 3W bulb on the ICON for bike commuting.. (and I also use a handlebar mount, usually a basic LED AA-based battery light on blink mode to be seen).
I think that was me...
One factor which has not received much attention in this thread is the light pattern. (We've simply mentioned broad vs narrow.) The Icon (high beam) has a rather narrow beam with a very sharp cutoff at the edges and dim side-spill. My best bike light (Nite Rider Minewt X2, LED, 130 lumens, handlebar mounted) also has a relatively narrow center bright spot with a smooth taper off to a lower intensity fairly wide side-spill. In biking (and other sports where you are moving fast) the center bright spot illuminates the distant path so you can see the obstacles ahead in time to react while the side-spill illuminates the nearby surrounding bushes and tredway/track/path. (IMO this pattern is a good match for biking.) In hiking (and sports where you are moving slowly) there is time to swivel your head to fill in the surround and much less need to see obstacles far ahead (navigation sometimes requires more light to see things far away). A lower intensity broad beam is, IMO, generally a good match for this.
For one reason or another, many have to use a single light for multiple activities but I like knowing (or at least to guesstimate) what would be best for each whether I can achieve it or not.
FWIW, the Apex has a very bright beam that is wider than the Icon's beam. The Apex has a reasonable-intensity side-spill, but its intensity is uneven with sharp edges within the side-spill.
FWIW2, the Icon only runs at 1.7W. BD advertises a 3W LED, but doesn't mention that they do not run it at full power. (The plastic-covered heatsinks are inadequate to run the LED at full power. It would overheat and burn out. Look at an Apex to see what "real" 3W heatsinks look like.) IMO, this is misleading advertising by BD.
FWIW3, on my road bike, I use a 1W narrow beam aimed in the distance, a 3W broader beam for the middle distance and surround, and a 1W light aimed down at the ground (to spot sticks etc) on my handlebars and an Aurora hiking light on my helmet (to stare down cars and light my instruments and view direction). (I often ride on a very dark bike path where nearly invisible pedestrians in dark clothing are a major hazard.) A mountain biker is likely to want a brighter wider pattern.
Doug