brake light ????????????

5 replies to this topic
  • jws

Posted June 16, 2003 - 09:24 PM


i would like to use the stock tail light as a brake light. i have the bd kit and would like clean it up a bit. i know i have seen it done before just forgot where.

thanks jeff :)

  • Dutch

Posted June 17, 2003 - 12:55 AM


I have seen where the stock bulb gets a resister wired in so when the brakes are applied the resister is bypassed and the light is brighter. I think Summers Racing does that. I just used a dual filament bulb socket and put an 1157 bulb in.

  • Rhino

Posted June 17, 2003 - 03:19 AM


About a year ago I followed these instructions that I got off the yahoo XR650 group to install a brake light on my xr6. It was posted by Ned. It worked for me, no problems with my brake light yet.

The only difference that I can remember was that instead of one 33 ohm resistor, I used several smaller resistors (5 ohm or 10 ohm, I can't remember which) in-line to get the desired effect as I couldn't find the 33 ohm resistor at the Radio Shack I went to.

Copy of the Email:

This email is intended to serve as instructions to anyone who wants to wire a brakelight on their dirtbike. The goal here is to leave the dirtbike with an operable taillight (running light) with a second, brighter stage displayed when the brake is actuated.

Why would you want to do this you ask? In my case, there were several reasons:
a) the enclosure that holds the taillight is very small. I couldn't find any aftermarket two filament solutions that would fit inside (although the stuff I got from Baja Designs came close... but it had other limitations).
:) the stock bulb is readily available at any auto parts store. The first aftermarket solution I wired in had a bulb made from unobtanium, leaving me tail-lightless very quickly
c) the stock assembly was very well engineered to absorb shock without breaking the bulb. Other options weren't.


1 working taillight- single filament bulb

1 brake light switch (I used a hydraulic one- be careful where you source them from, as the one I got from Baja Designs blew up and left me with no brakes on top of Black Bear Pass...- look for heavy duty metal construction).

1 33 ohm resistor (available at radio shack in packs of 5 for $0.79)
- This was the correct resistance for my XR. However, it has a weakish electrical system, and this might require some experimentation on your part.
- When sizing the resistor, look for 2 things. First, does it make the taillight roughly 1/2 as bright as when the resistor is out of the circuit? Second, if you leave the engine running and current routed through the resistor, does it get hot? It should get warm, but not hot...

I wound up trying 100 (way too dim running light, and loads
of heat), 47 (better) and settled on 33...

Assorted electrical connectors and lengths of wire. I was able to get connectors that matched those that came stock on my XR from radioshack- YMMV.

The wiring is very simple. In theory, what you are doing is routing the wire to the taillight through the resistor to leave only a portion of the current available to the bulb. You then add an alternate path around the resistor, switched to the brake. Now, when you activate the brake, an alternate, lower resistance path is available around the resistor, and all the current flows to the bulb, making it glow more brightly. For electrophobes like me, this seems
very neat and high tech (-:

In practice, follow these instructions:

1) leave one wire to the tailight as is. Do not modify.

2) Take the other wire to the tailight, cut, and create a "Y" on both ends of the separation you just made.

3) Take one side of both "Y"s and solder in the 33 ohm resistor.

4) Take the other side of both "Y"s and join to the brake light switch

5) Cover the whole project liberally with electrical tape, so that in the event you made a mistake, it's a real PITA to sort it out

6) Reassemble and impress officer law with you most excellent law-abiding behavior

I was able to route the wires to the brake switch down a sheath around the brake reservoir tube, leaving a very clean installation.

Anyway, I hope this is helpful to someone, somewhere. I couldn't find any good instructions (not that I looked that hard)... feel free to write and ask questions if you have any.


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  • jws

Posted June 17, 2003 - 09:45 AM


Dutch where did you get the dual filament bulb socket? does it fit ok? does it melt the tail light lens?

i was told that it does not fit to good and that it melts the lens.

i would like to go this route if it works

thanks jeff :)

  • Dutch

Posted June 17, 2003 - 01:50 PM


I had an old bike turn signal that was used as a running light. That needs a dual filament bulb so I used the socket. I bet most auto parts stores have them for sale. If you are carefull with the installation it can work.

  • jws

Posted June 17, 2003 - 04:27 PM


thanks for the info RHINO and DUTCH iam going to try the easy route if that dont work i will try the resistor way

thanks jeff :)

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