While every rider is different, most riders will have the most fun on the "Standard" Black resistance springs for Original Longboard trucks. The Standard Black springs offer the widest range of adjustment and were the springs Original trucks were originally designed to work with.

That being said, there is only so much resistance the standard spring can generate. You should only tighten your Original longboard trucks to the point where the top of the white WaveCam (plastic piece in the back of the truck) is flush with the top the metal tube that holds it.

If you like your trucks tighter than that, if you are coming from traditional longboard trucks (bushing resistance or dual spring resistance) or if you feel like you need more snap back to center out of the box, definitely try out a set of heavier tension springs; either in red (medium) or white (heavy) tensions.
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