Over the years the photos of this hack have been some of my most popular. Fall is coming and with shorter days I often ride with multiple lights for failsafe coverage.
This makes it easy to as a light mount to any M6 threaded brake post. This can be done on most modern brakes, canti, V, Paul Comp, etc., and with the Durace style cross pads I have even made this work on road calipers.
What you get:
To make this work just replace the outermost nut with the coupler. Tighten as usual with a 10mm wrench. Then add blinky light mount of choice. Some mounts may need the hole enlarged from M5 to M6, but many are ready to just bolt right on.
Why do this? Hard mounting a blinky with the plastic clamps that goes around tube often come loose or are a pain to get workign with all the little rubber shims. The rack bosses end up not letting the light mount at the right angle of view, and on and on. This just works well with no fuss after the initial set up.