rml127,

That's an excellent question. The consensus is often stated, "just enough spring tension to bring the arrow all the way back up, after pushing it down". However, I've never seen that in print from any rest manufacturer. In fact, I don't recall ever seeing ANY instructions on setting spring tension. Most everything you read and hear are people's opinions.

I can't disprove anything that Jim said, but I don't think he can prove them either. I do know that even a slight change in arrow tip height at the rest makes a pretty significant change in impact downrange. So, if the rest "flexes" on bad shots, I would argue that those shots are still going to be way off the mark.

I believe that the spring adjustment is there simply to allow the rest to be knocked out of the way when struck by a departing arrow. The "fine tune" comes in because you want a) the rest to swing away with zero resistance (ideally) if hit, so you set the spring as weak as possible and b) the rest to hold the arrow at the exact same point on every shot, so you set the spring with enough tension that it raises the arrow to a solid stop every time. If you don't have enough tension, the rest doesn't provide a repeatable nocking height. If you have too much tension, the arrow ends up being deflected as it leaves the bow.

As nice as it sounds, I don't think the spring is supposed to "smooth out" the departure. I don't think that would be repeatable enough to produce consistency.

Also, even if the tension is very low, if the arrow or fletching contact the rest, it will have an adverse effect. There is some force there that is resisting the way your arrow wants to go. That's what sold me on a drop-away style rest. I can shoot any arrow and not worry about clearance issues. Also, there's no worry about the rest performing some "magic" during the shot. If I've got flight problems, I KNOW that it's not the rest.

Not much "fact" there, I know, but at least you have another opinion to consider.