| the bridge feet don't have to spin. there's a threaded insert in the top portion of the bridge, and a "bushing" in the bottom part (so the top part of the bridge will move away from the bottom part and the wheel will stay at the bottom).
Clockwise should move the bridge taller, counter clockwise shorter. some wheels spin easier than others, I've used a wrench on mine (holding the feet in place so they don't spin). I also have a bass with wooden adjusters, those spin much more freely (i marked the spot with white out so i turn them the same amount, you need to keep them even distance when raising/lowering). My aluminum adjusters are very hard to turn the first few turns from all the way down, and then they move easier.
I've lowered the action with full string tension on, but for the first time you try it, lay it on it's back and loosen the strings some, there could be burrs, or even mis-thread (or off at a funny angle if the bridge is high on the threads). once you see how it moves, you can figure out what you can get away with.
You may also want to wait for more people to chime in, and make sure i don't have my head up my butt.
consensus is king |