Lowering is usually the way to go - it lengthens the power stroke of the bow a little (the distance the string travels from full draw back to its resting position). Although like most things in archery, experimentation may produce different results ;-)

 

I think you'd weaken your arrow more just by turning limb bolts in a quarter more, than playing with your brace height and probably ending up out of tune...

 

higher=weaker/lower=stiffer

 

far -

Raising the BH will -

Weaken the dynamic spine
Slow the arrow speed (slightly)
Increase the draw weight (slightly)

Lowering the BH will do the opposite.

Viper1 out.

 

I'm not sure but I think I just got both answers. I would like to agree with viper since that makes sense to me. I still see people however claiming that the increased power stroke of a shorter brace height weakens the arrow more. It also bothers me that OT2, which is fairly detailed software, weakens the projected dynamic spine when I lower the brace height.

 

I think the shorter brace = stiffer spine requirement in OT2 comes from modelling compound bows

 

Farsighted, it's not hard to test and then there's really no question in your mind. Viper is correct.

 

Viper is most definitely correct. His book, Shooting The Stickbow (one of the archery world's 'bibles') says so.

 

As usual, Viper is right.

The other thing that raising the brace ht. does is change the angle of the arrow on the rest, creating an arrow that's closer to centershot, which is another reason it softens the dynamic spine.

So much of this used to be "common knowlege" among traditional longbow and recurve shooters. Things like this were one of the few ways we had to properly tune our bows. Now that target bows are almost infinitely adjustable, and so many spine arrows are available, the fundamentals of setting up and tuning bows shot with fingers are being forgotten.

John

 

Thanks all for helping to clear that up.

 

another way to weaken the spine slightly is to use the forward plunger hole. the greater the distance between the arrow's contact with the bow's plunger and the bow string, the more the DynaSpine will be weakened. think of a pencil. If you want to break a pencil in half is it easier to grab it at both ends or put both hands next to each other.

its why a 34" ACE 550 is too weak for a 50 pound recurve but a 26" one is not

 

Great point Jim. Rarely do you ever see the forward plunger hole used for this purpose, but it's there and folks should take advantage of that!

John

 

+1 for the Viper

 

Thanks for the reference LKS.
Just ordered a copy of "Shooting The Stickbow".

 

As Jim C points out, "Brace Height" as we measure it has nothing to do with the distance from the hollow of the grip to the string. Rather it is the distance between the plunger and the string that are the tuning points. We use the grib as an easy reference. However when we talk about this or that "Brace height" it really is all relative to the positioning of the plunger in relation to the hollow of the grip.

Modern riser designs has gravitated to a plunger location somewhere close to the hollow of the grip. Not having measured every riser on the market I'd presume that there are suttle variances, manufacturer/riser to manufacturer/riser.

Testing as previously pointed out is the only definative answer to how your bow/arrow combination needs to be adjusted.

Regards,

Tom

 

Tom -

Think that goes into the overly splitting hairs category. Since most plunger holes are directly above the throat of the grip and since conventional wisdom is that a stick-on rest (without a plunger, for example on traditional bows) should be placed over the deepest part of the grip, the point becomes moot.

Further, for any given shooter, the brace height can be any distance on a given bow. For example, if a guy decides that he wants to call "his" brace height the distance from the string to the face of his riser, that's fine, since it will always be a constant on that bow. It won't make any sense when comparing different bows, of course.

I typically use a marking on the arrow in relation to a landmark on the riser or rest and don't need to pull out a bow square - on my bows.

Viper1 out.

 

In this video we adjusted the BH a little at a time from 9 1/4 down to 8 7/8. We needed to stiffen the arrow so it would bend a little faster to help with the clearance away the plunger. You can see the progression, and there was a definite an improvement.

 

Always here to learn, that's why I visit. Having re-read the Easton tuning guide, I can do nothing but agree with the far more experienced posters - so now you don't have opposing answers

But the Easton guide (for example) is conditional - there are other changes that go with raising the brace height - suggests you will get increased bow poundage but also a loss of arrow speed, and also suggests that the slight increase in draw weight does not equally compensate for the reduction in the power stroke. Soooo (thinking out loud) - the only certain way to get the result you want is to experiment (in both directions presumably, from your current setting, raising and lowering), until you produce the right result or admit the arrows is the wrong spine and buy some more

In this video we adjusted the BH a little at a time from 9 1/4 down to 8 7/8. We needed to stiffen the arrow so it would bend a little faster to help with the clearance away the plunger. You can see the progression, and there was a definite an improvement.

That's a really interesting video, but I'm not sure that what it shows is that the arrow reaction has been stiffened (in the way I understand it - i.e bends more/less /faster/slower). What I think I'm seeing is a very similar amount of bend in each shot, but the arrow is detaching from the string progressively closer to the button / rest, until you reach a point where the bend happens at a place when it ceases to cause a clearance issue...? I admit it's hard to be sure without measuring...

 

Great video. Thanks.

 

Gary, that's a great piece of work right there. Thanks for sharing.

John

 

I do this! Haha... Been using the forward plunger hole for my Nanos because the 830s I have spine a little bit stiff. Definitely helps with weaking the dynamic spine a bit.

 

Courtesy of Viper1:

 

So are ya sayin in the video the lower the BH the stiffer ya need??

 

Gurn, the lower the brace ht, the weaker arrow you need (or more point weight, or longer arrow).

John

 

I'm still confused then. Why in the Easton arrow chart does it have you add 5lbs for lower brace height which would be requiring a stiffer arrow for a lower B/H?

 

Based on the image posted above, does that mean that if I have a stiff arrow I could change my arrow from being just outside of centershot to being at true center?

 

Maybe not "true" center, but certianly very close to true center.

 

That is referring to compounds.

 

I would like to address this again somewhat, from some testing I did this weekend concerning brace-height. I shoot a W&W CXT 25" riser, with the WiaWis NS Graphene 34lb longs. These are 37lbs on the finger at anchor for me.

Over the weekend I did some brace height tuning, under the suggestion of a few books I read, because I just haven't had consistent grouping at 70m like I was expecting. My brace height that I used through indoor season was 232mm, and for indoor I averaged in the 270s; but out to 70m I just wasn't getting very good groupings. At 232mm my grouping was all over the place. So I increased my brace height to 235mm which is what I shot last year for outdoor, and my grouping got better, but when I missed the red/yellow the arrows nearly always drifted left. Even when bareshaft tuning, I noticed that if I had a errant bareshaft it always appeared stiff.

Anyway the books, Simon Needham, Archery the Art of Repetition, and Richard Cockrell, Modern Recurve Tuning suggested that adjusting the brace height will affect the release point of the arrow, and that if the brace height was too low that the arrows would appear stiff, and if too high the would appear weak, albeit they were not truly weak or stiff.

So I decided to see if there was some truth to that. I tightened my string 4 turns which moved my brace height from 235mm to 241mm, checked my tune at 30m, and sure enough my bareshafts shot center to center right of the fletched group. I backed up to 70m and shot a 36 arrow round, and two things happened. 1) When I missed the red/yel the arrows missed right instead of left and 2) my arrow speed increased some I'm assuming, because even though my sight marks didn't change at 18m they did change from 79 to 76 at 70m on a Shibuya.

I'm going to take two turns out of my string today, and drop my brace height down to 238mm (split the difference) and see what happens today.

 

Increased brace height will slow arrow speed, not increase it (with the increased brace height, the arrow is now not on the string for as much of the power stroke, thus not gaining that ending bit of acceleration). But the extra twists may have moved your nock point lower, thus increasing arrow elevation angle and overcoming the diminished arrow speed.