Know that truck tightness is a matter of personal preference. At the end of the day, there is no "perfect" amount to tighten your trucks. The tighter you turn the trucks, the more difficult the board is to turn. Too loose and you won't feel like you're stable, and your turns will be wide and difficult to control.The spot right in the middle of these extremes, your perfect tightness, is based on your own style and preference. Luckily, there is a large range of rideable tightness.
The amount the wheels tilt back and forth depends on how tight the trucks are. If you have a board (or a friend's board) that you like, test the tightness on them and try to replicate it in your own board. The amount they wobble right and left relates to how tight they are.
Use a skate tool or other useful tool to tighten or loosen the big nut in the center of the truck. This single bolt controls the tightness of the trucks. It points directly to the ground when you're skating, and is found between the wheels.
Remember that there is no "right" tightness-- you need to find out what works for you.
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