Resistor for BRAKE lights Question

[Strat Tuner]

If the current set up works, how about just replacing the plastic resistors with metal ones of the same value.

David! I think you've hit on the best overall solution. Thank you.

Things I think I know:
- there is NO way to wire this without a resistor
- resistors produce heat
- bigger resistors (50, not 10) produces MORE heat
- metal conducts heat more efficiently than ceramic

Thus, your solution seems best of all!

I think I will store two standard 1156 incandescent bulbs under the seat. That way, IF the thing fails on a long road trip, I can fix it by the road side. I can remove all the wiring for LEDs and Resistors and go back to what was.

I like those LED Brake light strips, and I have one in place above the license plate.
I'm considering adding one to the rear of the top box as well.
Wonder how the brake light circuit will tolerate that?

Best to test before drilling any holes!
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[Strat Tuner]

Would I make this change again? Hmmm.....

The answer is YES.

I'd Know (in advance this time)...

- the two brake light bulbs are white so that it can illuminate the brake light and the license plate at the same time. If you want that separate, you have to find another "always on" wire to light up the plate. That part was easy, comparatively, and I used two white light strips and pulled power from the rear "hella" power connector. That connector goes off when the key goes off, and it can light the plate independent of what the brake lights are doing!

- I'd know to use 10W, metal resistors and mount them OUT of the brake light enclosure so they may cool more easily.

- I'd know to carry spare incandescents to fix it by the roadside.

I realize that all of this doesn't apply to modern incarnations of the r1250. Any of you who have the more modern version, maybe you can tell me if the red brake light/running light is the same circuit?????
I hope it's not.
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Thanks for your time and attention.

[Doctor T]

Now seeing your wiring diagram I can see why the resistors burnt out. ground and live together is not a good way to connect them.
Awhile back I converted the large rear reflector on my China 52ltr topbox into a running/ brake light. 2 strip's of red LED. Whilst normal riding the LEDs just glow but when the brakes are applied they get brighter. I bought the lowest wattage LEDs I could find. Total watt was 1.42 Watts for both. I wirered them into the loom under the seat before the rear lights. Bit hit and miss at first as I didn't have a wiring diagram. I found the LEDs only triggered the Cambus on the turn signals.(wrongly Wired) Wired direct the stop bulbs sets off the Cambus but wiring before the bulbs on the loom didn't. Can't work out why as any extra draw of power should set it off
It seems to use LED strips without triggering the Cambus it must draw less than 1.5 watts total and be connected to the loom. I used no resistors

[David.]

The bulb is connected between ground and live with the resistor in parallel.

[David.]

It seems to use LED strips without triggering the Can-bus it must draw less than 1.5 watts total and be connected to the loom. I used no resistors.

Did you keep the original 21W filament bulbs and wire the LED strips in parallel.

Can't work out why as any extra draw of power should set it off.

The LED strips will draw an additional 0.125A, perhaps the Can-bus doesn't recognise such a small change in current.

[Doctor T]

Did you keep the original 21W filament bulbs and wire the LED strips in parallel.YES
I would like to try 2x running and stop LED with the topbox brake strips to see if that works May be my next project
The LED strips will draw an additional 0.125A, perhaps the Can-bus doesn't recognise such a small change in current.

Didnt seem to
Am an engineer and not an eletrician so if things don't work, I just try again and again. With the LED strip most are 5-10 watts. it took me ages to find 2 strip's that drew less then 1.5w total. The ones I used I think we're meant for diving/astronauts helmets, like those you see in films. Took me over 3 years to find them though a person via another person in the MOD.
I could have got 2 strip's with a total of 0.75 watts but they were very dull. Each strip contains 20 LED's

[Strat Tuner]

Now seeing your wiring diagram I can see why the resistors burnt out. ground and live together is not a good way to connect them.

I don't remember posting a wiring diagram? To what are you referring?
I did post this:
download/file.php?id=13141
That's the wiring diagram that came with the 10 W resistors. It's different than what I did by hand (I think), but I have no way to know for sure.

Without using the word "in parallel" , can you recommend the BEST way to wire in a resistor?

Those cute little "Lego" style diagrams are nonsense to me. Wires don't come that way. If two wires come together as one, you have to make a Y connector to get that to happen.

When you start with this, you have ONE red wire and ONE black that come from the motorcycle. ONE red connects to the light mount as does ONE black wire. If you want to put a resistor in that circle (circuit), you have to cut it both wires and do SOMETHING ELSE.

What is that something else?


I'm guessing you have to create a Y for the red and another Y for the black to create a red/black pair for BOTH the light and the resistor.

I'm going to draw it out in a way that makes sense to me, photograph illustrations, and post. This will take time since I'ma sitting in a Starbucks using my cell phone and an Amazon Fire HD10 to do this.
Here goes....
(See next post)

[Strat Tuner]

Let's see if I can import the hand drawings:
Before you do anything, you have ....

20250224_140102.jpg (269.35 KiB) Viewed 1998 times

As far as I understand, this is what you start with. It's simple circuit (circle) from motorcycle to LED light. Isn't it?

After you put in the resistor, you end up with something like this:

20250224_140800.jpg (293.61 KiB) Viewed 1993 times

I'm pretty sure that's what I have going now, but that graphic that came with the 10W resistors says it better.

Now, I could try something like this.... If I believed that a "resistor" was something that takes in electricity at one end and puts out 10W LESS out the other end.
(This seems intuitively wrong to me since the resistor has no black wire going to it!)

20250224_141055.jpg (289.2 KiB) Viewed 1993 times

Do resistors work like the 3rd illustration? NO black wire? Just a "pass thru" for red?

Doing something "in parallel" doesn't tell me where to connect wires.
I suspect there is a "BEST" way to wire this... One that makes CanBus happy and generates minimal heat.
'Gosh... I wish knew what that was.
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[Strat Tuner]

The bulb is connected between ground and live with the resistor in parallel.

AAAAAAAAAaaaaahhhhhhh!

[David.]

In the second illustration, the resistor is wired in parallel with the LED.

In the third illustration, the resistor is wired in series with the LED.

Parallel is the correct way to do it.

[Strat Tuner]

The new resistors arrived.
They look like this

wire1.jpg (30.34 KiB) Viewed 1942 times

I'm guessing I should wire one black and one red to it...just like the ceramic.

Does it matter which wire goes to which end?

[David.]

Does it matter which wire goes to which end.

No.

[Strat Tuner]

I'll start where I finished.. with the photo.

wire3.jpg (248.15 KiB) Viewed 1667 times

- put new aluminium resistors in
- Everything worked (resistors got really hot just in the garage!)
- Added another LED strip along the trailing edge of the top box platform (will canbus tolerate that?)
- CanBus didn't mind

- stood back and thought about things for a long time

Adding the second led strip ABOVE the factory brake light made a big difference! With that in, did I really need LED bulbs in the factory tail light housing? Maybe, but NOT at the expense of peace.

There's NO peace riding along on a potential fire hazzard.

I decided to strip out BOTH RESISTORS and put in one 1156 standard incandescent mated with the one LED bulb that would work with CanBus. I tested those two early on looking for something that would work with CanBus and NO resistors. In the photo, that accounts for one side being brighter than the other inside the factory tail light. Now, I can roadside repair it by carrying two duplicate bulbs under the seat!

I could have put in two 1156, white, filament, incandescent bulbs... which is what was there to to start with.

The two LED strips, one at the top of the plate and the other on the top box platform, do a bang up job! ... AND.... there are NO resistors!

It would be visually better if one of the LED strips were completely OFF and came on only when I apply the brakes, but that's not possible.

Here's the LED strip I like best. It can even double as turn indicators, but you don't have to use that.

strip1.jpg (174.8 KiB) Viewed 1659 times

or you can search with

LivTee Universal 8" Flexible LED Light Strip with Tail Brake Stop Turn Signal Lights All-in-one for Motorcycle Scooter Quad Cruiser Off Road, Red/Amber

(NO, I didn't have my license plate changed for real, but I'm delighted to finally understand what "In Parallel" means.)
Thank you for your time and patience.
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[Doctor T]

The two LED strips, one at the top of the plate and the other on the top box platform, do a bang up job! ... AND.... there are NO resistors!
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A bit confused by your statement say "there are no resistors" If none were needed. can you explain or expand why did you buy resistors in the first place?
Has the strip's resistors built in?

[Strat Tuner]

Resistors are required if you want two LED bulbs as brake lights. Best brightness and longevity.

CanBus will not accept two LED bulbs without resistors.

I bought resistors so I could use two LED bulbs. I'm not using two LED bulbs now, so no resistors.

Strips have no built-in resistors. CanBus tolerates them maybe because strips patch in under the seat and NOT inside brake light housing??

I only know what works... not why.

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