What exactly does changing brace height do to arrow tuning?

[Nativestranger]

Ok I have seen many conflicting information on brace height. Some say increasing brace height makes your arrow tune weaker because of increasing the draw weight slightly some says reducing it makes the arrow weaker because there's now more energy from the increase power stroke. Some say it has to do with changing the centershot. Now I am confused. Has anyone done a scientific test on this?

[Pheonixarcher]

If you do a search here, there have been a few recent threads covering this topic in detail.

Effectively, the angle of the arrow is changed (11 o clock with a 9" brace to 10 o clock with a 7" brace as an example).

But the simplest way I have found of thinking about it is a stronger but shorter push with a higher brace, and a weaker but longer push with a lower brace. The stronger the push, the dynamically weaker the arrow shaft.

[mgf]

The only science you need is to try it.

I say that raising the brace height makes the arrow show weaker for the reasons that Pheonixarcher mentions.

I tend to think it has more to do with the change in arrow angle (like thinning or thickening the strike plate) but I couldn't prove it.

[Trond]

This is copied off the result page of 3Rivers spine calculator:

Fine tuning can then be done by adjusting the bow's brace height.  
•If the arrow is slightly weak (lower dynamic spine) for what the bow needs, then lower the brace height.
•If the arrow is slightly stiff (higher dynamic spine) for what the bow needs, then raise the brace height.

[Trond]

This illustrates it:
 

[Nativestranger]

But isn't the arrow supposed to be not touching the bow but bending clear at that point during the shot? Seems most here agree that longer brace height = weaker arrow.

[Bladepeek]

I'm a subscriber to the change in angle theory illustrated above in Trond's post. The arrow does bend around the bow, but look at the angle at which it is pointing - that will determine the point of impact. I have also found that center cut makes a huge difference in how much change occurs.

I have a Blacktail Snakebit that is cut so far past center that even with a fairly bulky Velcro sideplate, the arrow is still sitting very close to center. I can shoot that bow with a brace height of 6 1/4" all the way up to 8 1/4" and see almost no change in point of impact (also there is very little change in sound or hand shock on this bow). On my "D" type longbows that are well proud of center even before a sideplate is attached, I can generate quite a large change in point of impact from 6 1/2" to 7 1/4". There is also quite a bit of difference in the feel and sound of these bows, so I tune the bow for best feel/sound and then tune the arrow to the bow at that brace height.

Just one guy's take on it.

[Cavscout9753]

I've always gone by what's been said already, raising the brace makes the arrow act weaker, lowering it makes it act stiffer. I say "makes it act" because like the others illustrated, I don't think it actually stiffens or weakens spine but rather the angle makes it act as though it did. In the end I just treat it as a final tweak for tuning. Whatever effect I've seen it have has varied in degree by which bow I'm tuning or arrows I'm tuning. For recurves it gets tricky because brace has a good deal to do with how noisey a bow is and how well mannered it can be so it'a really a "robbing peter to pay paul" thing: I'll tune brace for noise and then strike plate and arrow for spine. But I agree, whatever reaction, benefit, or loss just has to be found by each shooter and each bow.

[olddogrib]

If you search it's one of the most debated topics that frequently comes up and it sounds paradoxical, pardon the archery pun. Folks still defend the "power stroke" argument, but think about it this way.  An arrow that may typically start out pointing very slightly left(for a RH archer)of the string/riser centerline oscillates in such a fashion to flex around the riser and continue down a straight line, not as it was pointing. If you lower brace height it has the effect of delaying the moment of nock detachment from the string, affecting paradox(less wrap) in a way that brings point of impact back to the left. Conversely, raising brace will allow the nock to detach earlier, accentuating paradox(more wrap) and impacting further right.  In either case the arrow spine is what it is, brace height just allows very slight compensation if it's slightly weak/stiff.

[**DONOTDELETE**]

Originally posted by Bladepeek:
I'm a subscriber to the change in angle theory illustrated above in Trond's post. The arrow does bend around the bow, but look at the angle at which it is pointing - that will determine the point of impact. I have also found that center cut makes a huge difference in how much change occurs.

I have a Blacktail Snakebit that is cut so far past center that even with a fairly bulky Velcro sideplate, the arrow is still sitting very close to center. I can shoot that bow with a brace height of 6 1/4" all the way up to 8 1/4" and see almost no change in point of impact (also there is very little change in sound or hand shock on this bow). On my "D" type longbows that are well proud of center even before a sideplate is attached, I can generate quite a large change in point of impact from 6 1/2" to 7 1/4". There is also quite a bit of difference in the feel and sound of these bows, so I tune the bow for best feel/sound and then tune the arrow to the bow at that brace height.

Just one guy's take on it.

I think Bladepeeks description pretty well sums it up here..... The amount the bow is cut past or too center has a huge impact.....

The only thing i might add to this which also aggrees with Bladepeeks description is that when raising and lowering your brace height above or below the optimum brace for that design, you need to factor in the efficiency loss....

There is a belief out there that lower brace heights lengthen the power stroke and therefore increase efficiency....

This is wrong.... there is no debating it. Its a fact.

Every bow has an optimum brace height where the string tension at brace is at it's peak and it has the best pre load.... adjusting it higher, or lower than that sweet spot you will loose stored energy, give you more noise and vibration........  

Find the sweet spot, and tune your arrows to the bow for best results.....  

There are some guys that do not mind loosing a bit of efficiency and will use brace height to fine tune an arrow that is showing weak... and that will work.... But  I would save that for a last resort and keep your bow quieter.

[mahantango]

As usual, Kirk is spot-on.

[Nativestranger]

Thanks alot for the info guys!

[katman]

Best thread on the explanation I have read, thanks guys.