Introduction: Bicycle Tail Light (or Headlight) for Under $5

About: wow, writing things about myself is hard. Modded Leatherman wave always at my side, ill dive into repairing a computer, a diesel truck or a doorknob with the enthusiasm that confuses people. Knowledge of a &…

Lately I've been getting back into riding bicycles with my family. The
problem is I ride a lot at night after work and we need lights. After looking at how much a "typical" set of lights cost ($20 USD for a tail light alone), I knew I can do better and cheaper than a single LED that can barely be seen from 20 feet at night. As I was wandering down the aisles of my local Harbor Freight one day, I came upon inspiration in the form of the $3.99 "emergency 39 LED triangle work light" and knew I found my tail lights. They have 3 modes, red triangle, white triangle and red FLASHING triangle, actuated by a single button. For this instructable, since we're focusing on the rear half of the bike (I use a cree 450 lumen flashlight I bought at Aldi's for a head light) I will only refer to the red lights in this from here out.

Step 1: Items, Tools and Time:

Items that I used:

(1) 1/4" x 1" bolt

(1) 1/4" regular nut
(1) 1/4" locking nut
(2) 1/4" flat washers

(1) 3/8" flat washer

Phillips screwdriver

(2) 7/16" wrench
OR Vice grips

Time to make them:
10 minutes

Step 2: Disassembly

First remove the warning stickers. You can't take off the back with them on.

Remove the two screws from the back of the light. this is where you put in the 3AAA batteries.
Remove the back of the housing from the light and flip it over. Center the magnet over an empty space so that you can pop the magnet out of the hole with the phillips screw driver.

Step 3: Install the Bolt

Put the 1/4" and 3/8" washer on the bolt and insert through the housing.
Place 2 1/4" washers then the nut on the back of the housing.
Use your 7/16" wrenches (or wrench and vice grip) to tighten them so that nothing will turn when you mount to reflector hole.

Step 4: Mount to Bike, Enjoy the Night Ride Safely!

Since every bike is different, I'm not going to detail pictures of the installation.
Remove your rear reflector, put the mounting stud of the light in the hole, tighten down the lock nut. Use the two wrench setup to make sure it doesn't move.
I mounted the lights with the button on the bottom in hopes to keep them a little more water resistant if I get stuck in the rain. At $4.00 with batteries already installed, I'm not too worried about it shorting out, I'll just buy another one.

I like to use the flashing red lights the most. It seems to get the most attention. The white ones work great for finding the garage door lock at night when we leave. In the solid red mode, I've noticed a red "glow" on the street 10 to 15 feet behind me, and I can see these lights for over 200 feet away when we're riding in flashing and solid red modes.

In case you were wondering, the trike is a custom built cruiser that I am building into a show bike. The other ones are what my wife and I usually ride.