To make LEDs work right you need to put load equalizer on. Put LEDs in mine, lights did weird things, work great with load equalizer.
You don't need the resistor unless you put LEDs in the front and rear signals. If this is the case, then yes you'll need to put them in. Are your rear signals your brake lights also? I'd make sure the bulbs are dual filament as well.
Just installed the "Badlands" version of the stock rear yellow, bulb turnsignalonly setup, conversion to red lenses with red LED turn signal lights which go to brighter when you hit the brakes and are always on normally, giving you 3 lit reds across the back at all times and 3 brake lights. The 2 turn signal LEDs [there must be 40 LED bulbs in a cluster on each side] are very bright and highly visible in daylight. They wouldn't blink at first which I traced to a bad ground [my bad] at their included module. I think it is a very nice looking and important upgrade safetywise.
Is an equalizer still needed for the nightster. I just got the Joker LED's for the rear and was assuming I didn't need one because the tailights are already setup to be running,brake and signal. I've noticed though that I have 3 wires going into the factory bulbs(black,purple and blue) but only 2 wires coming from my new Joker LED's(black & purple). Whats this blue wire for?