# what is the effect of brace height on tuning?



## tjk009 (Feb 15, 2007)

I received a new string from K-1, and it is beautifully made. Started at 8 5/8" and my groups were good at 8 1/2" brace height as the string stretched. I usually shoot at least 8 5/8" but my bow is vibrating more than with the other string. Now the stretch is over and at 8 5/8" the groups aren't as tight. The string is Angel 14 strand. Previously when my bow rattled I cranked the brace height to almost 9". Samick limbs, 36 lbs, ACE 670, 68" bow if that matters. So, what is the effect of a higher vs. lower brace height....advantages and disadvantages and should I go up or down? Thanks.


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## calbowdude (Feb 13, 2005)

Yup, Friedhelm makes good strings. 

If you increase the brace height, you will cause the arrow to tune weaker. If you decrease, you will cause the arrow to tune stiffer.

If you go too low on brace height, your bow will most likely get noisier and noisier, as the string slaps the limbs more. 

As far as the bow shooting better at a given brace height, if you're noticing this, then go ahead and twist the string up to get the brace height back where you got good groups. Make sure to twist the same direction as the serving, so you don't unwind the serving. 

There are some shooters that raise and lower brace height and listen for a quieter vs a noisier bow.


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## daMatt (Jun 9, 2006)

*some simple advice...*

hey, 

I work in an archery pro-shop and the brace height does affect your tune (pretty much what the above guy said).

the shorter your brace height, the longer the arrow is on the string and the more speed/power on the arrow you get and this makes your arrow tune weak.

the longer your brace height, the shorter the time is for the arrow to be on the string. now yes, the string doesn't stop right there but it doesn't get as close to your riser. this causes the arrow to be stiff.

every bow in itself has its own specific brace height and tiller length. the top tiller should be 1/8" to 0" longer than the bottom. I keep my tiller at about 1/16" (not exact science here) and it keeps the bow very quiet.

How long is your bow?

good luck


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## Steve N (Apr 27, 2004)

Looks to me like contradictory info between Calbowdude and daMatt. Which is it: shorter (decrease) brace height = arrow tunes stiff, or the other way around? Or am I reading these two posts wrong?


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## tjk009 (Feb 15, 2007)

My concern in getting the faster string is to make it to 90m with 36# limbs a little easier. I don't mind a little noise for more speed and power. So are those the tradeoffs?


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## Jim C (Oct 15, 2002)

Steve N said:


> Looks to me like contradictory info between Calbowdude and daMatt. Which is it: shorter (decrease) brace height = arrow tunes stiff, or the other way around? Or am I reading these two posts wrong?


Here is the correct answer:wink:

1) A lower brace height does the following

a) is slightly less forgiving to bad form since the arrow stays on the string longer

b) is slightly FASTER because of the increased POWER STROKE

c) makes the arrow shoot SLIGHTLY STIFFER because the actual weight of the bow is decreased by a longer string


2) A higher Brace height does the following

a) is slightly more forgiving due to the arrow being on the string slightly shorter period of time

b) loses a small bit of velocity due to the decreased power stroke

c) since raising the brace height compresses the limbs and increases the weight, the arrows act slightly WEAKER


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## Targetbutt (Jan 19, 2006)

The difference in speed of higher vs lower brace height is miniscule. I went through an excercise recently with a chrono. I went in 1/8" increment on brace height, shooting 16 arrows at each height. Throughout the range of brace heights, the speed difference between groups is in the order of .25 to .75 fps. While within the group, I have differences of about 1 to 1.8 fps between shots. So, set the brace height where the bow will be the most quiet, your bow will thank you and so will the person shooting next to you :wink:


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## Jim C (Oct 15, 2002)

Targetbutt said:


> The difference in speed of higher vs lower brace height is miniscule. I went through an excercise recently with a chrono. I went in 1/8" increment on brace height, shooting 16 arrows at each height. Throughout the range of brace heights, the speed difference between groups is in the order of .25 to .75 fps. While within the group, I have differences of about 1 to 1.8 fps between shots. So, set the brace height where the bow will be the most quiet, your bow will thank you and so will the person shooting next to you :wink:


True-its the tuning and noise that I worry about when adjusting brace height, not speed. Playing around with bowstrings is another way. I tend to stay away from the thin strings some are enamored with-18 Strands of 8125 or majesty I find is far more stable than the 14 strands some advocate even though you do pick up a little bit of speed with those thinner jobs.


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## Targetbutt (Jan 19, 2006)

Yea, I tried the chrono thing, thinking that since my ear is not so good at picking up subtle differences in the noise I can use an electronic help. But in the end my ear came out ahead of the chrono.


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## calbowdude (Feb 13, 2005)

What JimC said. 

Given a choice, I would tune for good groups and noise rather than for speed. I am a bit surprised by the minimal effect brace height had on speed, since Hoyt's recurve manuals suggest a larger velocity change when lowering brace height.


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## Jim C (Oct 15, 2002)

calbowdude said:


> What JimC said.
> 
> Given a choice, I would tune for good groups and noise rather than for speed. I am a bit surprised by the minimal effect brace height had on speed, since Hoyt's recurve manuals suggest a larger velocity change when lowering brace height.


That was one of the selling points of the FX limbs


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## calbowdude (Feb 13, 2005)

I do remember that the FX took something like 1/2" less brace height than normal. Is that the primary source of its vaunted speed? You haven't gotten a chance to compare Winex or Samick vs FX yet have your?


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## Jim C (Oct 15, 2002)

calbowdude said:


> I do remember that the FX took something like 1/2" less brace height than normal. Is that the primary source of its vaunted speed? You haven't gotten a chance to compare Winex or Samick vs FX yet have your?


Yes it was-a had a set of 42 M FX (Doug Pace is using them now) and I compared them to G3 MI and PSE-Xpressions-using the same braceheight (which is tricky since the G3 and MI require a slightly shorter string) there was no noticeable difference in speed and if you set the G3 at say 8.25 rather than the 9" I normally do for Med Limbs on a 25" riser they were as fast as the FX. The FX is smooth but they vibrate noticeably on the shot-several years ago Jason McKittrick noted that he had used ultracam or a similar vectran based string to "calm down" the FX but lost some speed doing that,

I shoot G3 on my main bows or MI but I used Winex (thanks to Recordkeeper's great deal) indoors on a helix. I like the WINEX very much but they are longs and thus the smoothness compared to the medium Hoyt and PSE/WW limbs is difficult to compare. Wormburner sold me a nice set of Long MI and they are as smooth, though slightly slower than the same length/marked weight (a hoyt 38 is lighter than a WW 38lb limb btw) Winex limb


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## Duss (May 23, 2006)

Increasing the bracing height actually can be used to "weaken" arrows.

For long-distance shooting, one of the best methods I have experimented is the "efficiency tuning".

You start with the medium recommended bracing height for your riser and limbs. Check and adjust your tiller and nocking point height. Then shoot at 50 meters and note the sight mark.

Do that again after increasing/decreasing the bracing height. Always re-do the nocking point adjustment and tiller verification and adjustment.

You will find a bracing height for which your sight gets higher and at the same time youw bow,s "sound" should be the smoothest.

That procedure may look long but it really yields the better results in terms of efficiency. It can be verified at other distances.

I have recently tuned two bows for long-distance FITAand the effects have been very much noticeable. In the first case, the 90m distance is now reached without shortening the sight bar. The sight marks have risen by at least 3/8" and the spread has "flattened".


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## Joe T (Apr 5, 2003)

The FX had a tapered core giving a lighter limb tip section hence higher speed. I would guess that the lower brace height was used to attempt to stiffen the limb tip making it more stable and to shift the energy storage lower down the limb.


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## Duss (May 23, 2006)

Oops! I forgot to mention that in the "efficiency tuning" routine one must also re-check and re-adjust the Berger button's pressure in case the arrows' dynamic stiffness changes


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## Jim C (Oct 15, 2002)

Joe T said:


> The FX had a tapered core giving a lighter limb tip section hence higher speed. I would guess that the lower brace height was used to attempt to stiffen the limb tip making it more stable and to shift the energy storage lower down the limb.


equivalent brace heights on other limbs usually resulted in equivalent speeds compared to the FX -at least from what my testing found including the wood-carbon Sky Jack Limbs


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## Jim C (Oct 15, 2002)

Someone I know who is an expert in this area noted that the higher brace height may cause stiffer arrows to tune slightly weaker is because the higher brace height increases the distance from nocking point to plunger which makes the arrow behave slightly weaker. Its like putting your plunger in the forward (towards target) hole for stiff arrows-something Vittorio mentioned in his book

after thinking about this explanation it makes as much or more sense as the common belief higher brace height=heavier draw weight


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## Progen (Mar 17, 2006)

A little curious about the string material. If it's Angel ASB Dyneema at 14 strands, then that'd be a rather thin string, wouldn't it? I found that 16 strands of Majesty was a teeny weeny bit smaller in diameter than 18 strands of ASB Dyneema. Used the same serving.


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## Jim C (Oct 15, 2002)

Progen said:


> A little curious about the string material. If it's Angel ASB Dyneema at 14 strands, then that'd be a rather thin string, wouldn't it? I found that 16 strands of Majesty was a teeny weeny bit smaller in diameter than 18 strands of ASB Dyneema. Used the same serving.


angel recommends 18-20. 18 with the majesty serving fits the larger pin nocks well IMHO


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