Are they for upholding pickup weight?
It seems logical, but pickups are not very heavy, so I don't think that's the reason that they really are for.

or are they?
They counteract against springs or foam undrneath the pickup. Tighten to compress the springs, lowering the height, loosen to contract the springs, increasing the height.

Edit: misread. Springs produce force that opposes the force of the screw. This allows for a position to stay constant for far longer than foam.
Last edited by Deliriumbassist at Oct 26, 2014,
They keep your pups from just flopping around in the hole by keeping tension on them at all times. Without the springs the adjustment screws would also just slide freely in the pup ring holes, making adjusting height about impossible. This may not be the clearest explanation, but it's about the easiest way I can describe it.

This is if you're talking about ring mounted pups and not direct mounted. I don't think I ever seen springs on a direct mounted pup, they usually just have foam, wood shims or nothing at all under them to set the height.
Last edited by Way Cool JR. at Oct 26, 2014,
Yeah, pickup rings are usually not threaded so the it's the spring resistance that holds the pickup down.
Charvel DX-1 FR / DS-1 ST / DC-1 FR / Custom Strat / La Patrie Hybrid CW / Vypyr 30 / VK100 / 1960A
Last edited by Danustar at Oct 27, 2014,