audioguru makes a very valid point. You have to account for the swing of the vehicles supply voltage. You could use a standard TO-220 package 7809 , 9 volt regulator, and setup strings of say 4 LED's with parallel runs like the pictures above. Each run should have its own series resistor. Slight increase in cost, maybe 1 dollar for the regulator, but a better result.
PS , nice ride musthave! don't see many of them anymore.
Thanks zevon8 for the compliment. To integraoligist give it a try experiment on breadboard first to see if you get the result youre looking for , mine i tryed one row and it was to dim then 2 rows then 3 rows and it was real good . here is my schematic hope it helps you out a litle im no pro just a hobbyist. **broken link removed**
Here is a link to a car's tail-light circuit: https://www.redcircuits.com/Page85.htm
It uses a constant current sink which automatically adjusts for changing battery voltage.
Caution: The LED current is very high and might exceed the max rating of your LEDs.
It seems to have too many LEDs in series to operate with a battery voltage as low as 11V, maybe only 4 or 5 LEDs in each series string is best. :lol:
With an 11V minimum supply, an LM317 set to 9V or a 7809 would regulate the voltage (their supply voltage must be at least 2V more than their output). Then the current-limiting resistors for brightness control would need re-calculation or experimenting.
The tail-lights would need to be on all the time or the brake lights won't work.