K Bike Tech

LED Brake & Tail Lights

LEDs are much brighter and better these days than they used to be. I decided to experiment with some different LED tail and brake LED bulbs to improve K visibility from the rear.

Both the brake and tail lights have a standard BA15S base.

Tail Light:

I've been using the amber version of these in turn signals and they are much brighter than a filament bulb so instead of testing a bunch of different ones I just use this one in red. It has 144 3014 SMD LEDs - 18 at the tip and 21 rows of six around the sides.

It is/is not BMU "friendly."

Tail Light:

The stock 10 watt tail light bulb is, in a word, wimpy. I suppose the reason BMW used such a dim bulb was to make the brake light more obvious when the brakes are applied but in dark and/or rainy conditions the tail light is hard to see so you won't be very obvious to people driving behind you. Note also that the brake compartment of the rear K lens has a silver reflective coating while the tail compartment does not which doesn't help.

The 10 watt stock tail light bulb is shorter than a regular 1156 bulb and usually looks like one of these:

Because these bulbs are small the tail light compartment in a K's brake/tail lens is accordingly small and will not accommodate a regular sized 1156 bulb like the 21 watt bulb used for the brake light:

After a bunch of measuring and searching I picked four small 1156 red LED bulbs that I thought had potential to work well as tail lights. All of them are short enough to fit in the tail light lens and small enough in diameter (20mm or less) as well. Since the rear lens is red I tested the red versions of these LED bulbs. (If you use a white LED behind a red lens then the lighting appears pink.)

I chose not to post up pictures since pictures of LEDs, especially red ones, can be deceiving. Here's a table of my subjective opinions of the four different LED bulbs.

LED Bulb	Observations	BMU Friendly?	My Rating
A - 12 x 3030
B - 19 x 4014
C - 57 x 3014
D - 10 x 3030

A note on claimed lumen outputs: Vendors claims of lumen output should not be used to evaluate how bright a light will be in real life. Here's the short version of why not:

* There is no standardized way to measure effective lumens.

* Effective lumen output can vary greatly depending up the reflector and lens used.

* Vendors lie. Many times the lumen figure they quote is the theoretical maximum of the LEDs used, not the effective lumens that the LEDs actually emit.