Rangeball

When a manufacturer states the specs for a bow, is it done with the limb bolts fully seated? If no, how is the bow configured when it is done?

Rack-attack

I think the specs and speeds are done with bolts down (full weight)

This is the main reason IMO a 70 bow does not shoot as fast at 60 as a 60 bow does. Because as you let the bolts out your brace increases.

But I would not be surprised if they measure speed bottomed out then measure brace with the bolts let out......[:-]

tricky I tell you......tricky

Double Creek

IMO, that is exactly what they do! I've been doing some measurements myself and that is the only explanation.

PABowhntr

...and also because there is not as much prestress on the limbs.

Rack-attack

Interesting..................

Isn't 60lbs - 60lbs?

Both bows are prestressed 60lbs - the 70lb limbs are stressed lower than there "working" max, but expain how having more "potential" of stress will lower bow efficiency.

I am not saying your wrong - I just don't understand how it would effect speed.

Rangeball

I figured it was due to the brace issue as well as cam not being optimally positioned, which could probably be fudged with to eat up the 4-5fps difference you're likely to see between a maxed out versus backed down...

Bowtech Dually

They may both be set at 60 lbs. but if you compare a 60 lb limb to a 70 lb limb the 70 lb limb is thicker and therefore heavier, I would guess that due to less weight and more prestress this is why the 60 lb limb would shoot faster than the 70lb limb when both are set at 60 lbs.
BD

PABowhntr

BD is partially correct as I am sure that limb thickness plays a part. You must also consider though that any given bow is designed to operate most efficiently at peak weight. Adding any adjustment to the system, in this case the draw weight via the limbs, can take away from that specific level of efficiency because the bow is now operating under a different set of physical conditions. It may only be a marginal difference but it is there none the less.