Explain Brace Height

[tracker12]

So every bowyer gives you a recommended brace height.  But what determines that number. And when is it right.   I have a 66"  Slammer and Leon recommends 7" and I have another that the bowyer says start at 7 1/2.  My RER LX came with a recommended start height of 7 7/8.  So i adjusting BH what do you look for.

[ranger 3]

Sound and feel

[McDave]

Most people I know just set the brace height at the bowyer's recommendation and leave it at that.  I can tell by watching the erratic arrow flight when somebody ignores their brace height and lets it get too low from string stretch.  Evidently, twisting it up too high will reduce the efficiency of the bow, but this is not as easy to see.

Adjusting brace height within the recommended range makes subtle differences in bow performance, but may not be evident unless you have really good form.

The rule of thumb is to set it as low as you can until noise and/or performance begins to deteriorate.  This is because bow efficiency increases as the brace height decreases, to a point.

[hoo-ray]

Setting it to low can make it hard to tune.  Learned this the hard way on a recurve.  Spend a little time and play with brace height.  Find that "sweet" spot.  It's there somewhere.   Josh

[**DONOTDELETE**]

How does the bowyer determine the sweet spot to recommend?  That would be a better question i'm thinking.

It can be determined many different ways actually. Some guys have built enough bows to just do it by feel & twist it up or down a bit until you get a dull thud instead of abuzz with a bare string.

Another way is to put the bow in a shooting machine and use the same arrow at the same exact draw length and shoot it at different brace heights until it reaches the max performance. That is going to be the best brace height for noise, vibration & speed.

The best brace height for a bow is when the string is at it's tightest point.... as you increase you brace it peaks out and continuing to raise the brace height actually lowers the tension on the string.

There is another way to determine the highest tension on the string, but it's a little high tech for the average archer, and kind of a spendy instrument. You can use a cable tensiometer....

There are a lot of guys out there that use their brace height to fine tune arrows. As a bowyer i wouldn't recommend this procedure unless it's very conservative..... Once you get outside of the recommended brace height parameters, it's going to cost you in efficiency and add unwanted vibration to your bow.

[Gapmaster]

There are a lot of guys out there that use their brace height to fine tune arrows. As a bowyer i wouldn't recommend this procedure unless it's very conservative.....  

WOW----What is your definition of conservative? Because I thought most top bowyers recommended these adjustments. When you use the machine to find your brace height (if that is what you do), are you talking accuracy, speed or vibration to arrive at what you think it should be? So really the reason I'm questioning is because everyone I know uses brace height to tune their bows. Any help you can explain to me on this subject would be greatly appreciated for not just me, but I'm sure a whole bunch of readers.

[**DONOTDELETE**]

The sweet spot in the brace usually has about a half inch variance before adverse effects come into play. If a bowyer recommends 7"-7.5" brace, and the archer has it on the top end of it. Running it up to 8" to help tune arrows is going to decrease the tension on the string and cause more limb oscillation after the arrow leaves the string..... Some limb designs are more tolerant than others in this respect, and higher draw weight bows will see less adverse effects too because the tension on the string at brace is higher on a higher draw weight bow.

People often confuse the term "High performance" with just arrow speed.... High performance in a bow is one that has the least vibration and noise it can possibly have, which always gives you better arrow speed & a flatter trajectory.

Arrows should be tuned to the bow, and the bow can  be fine tuned using the strike location and adjusting brace "Within the bowyers recommended brace height parameters.".... The lighter GPP arrow you use, the more critical these adjustments become.

[katman]

Great info there Kirk.  

[Krex1010]

When adjusting brace height I'm assuming you leave one end Attatched to the limb and twist or untwist the string....does it matter which end you do this from? Also is there any general rule as to how many twists will correlate to a specific amount of change? ( 5 twists=1 inch, for example) I've never adjusted brace height but my string has definitely stretched and now my brace height is a solid inch under the recommended range.

[Stumpkiller]

Originally posted by Kirkll:
The best brace height for a bow is when the string is at it's tightest point.... as you increase you brace it peaks out and continuing to raise the brace height actually lowers the tension on the string.

I know I'm going to regret this as I am not a bowyer, but . . . W'huh?  

Raising the brace height can lower the string tension?  So at some point the bow tension is less as you pull the tips together?  I'm not understanding that.  The rate of change - sure.  But not the net pressure.

Isn't that preloading the bow and putting more on the string?  I've never seen a draw-graph for a recurve or longbow that dipped - they're usually linear and increasing

[Krex1010]

Stumpkiller....you're not alone, I'm sitting here trying to figure out how string tension can start to decrease by shortening the string, if it's really the case I'm missing something.  Would love to hear some more on that subject, Kirk learn me a little please! Lol

[kbaknife]

Another factor is that the lower the brace height, the longer - time - the forward traveling arrow is under the influence of the limbs, because the limb tips are able to travel farther forward.
If you increase the brace height, by shortening the string, and your draw length remains a constant, the limb tips are now farther back at release, but come to a halt sooner. So even though the arrow's forward travel may begin at a faster speed it gains forward inertia for a shorter period of time.
All sorts of gadgets would be necessary to determine where the laws of diminishing/increasing returns are a benefit or a deficit.
Or - just adjust until it's quiet.

[Charlie Lamb]

Loads of good technical info already posted. Here's a look at it from a basic view.

You first have to try to match your arrows as closely to the bow as possible. Though it's hard to guess perfect it's not impossible.

Next consider these to things... brace height basically affects the way the arrow stabilizes from side to side. (fishtailing)
Nocking point affects how the arrow stabilizes up and down. (porpoising)

With both adjustments it better to start with them too high than too low.
For brace height I'd go with the bowyers suggested height on the high side. Example...7" to 7 1/2" set the brace at 7 1/2".

Shoot a half dozen arrows at that setting and watch to see if there is any fishtailing. (probably not)
If all looks good lower the brace an 1/8" and shoot six more.
Keep doing this until you sees a change in arrow flight. At that time raise the brace and see if things get better. Do this until the arrow flies perfectly.

This will give you your fastest straight flying arrow and a quiet bow.

Repeat this process with your nocking point. More sophisticated tuning comes after your form settles in.