What is meant by “Tuning your bow”
The necessity of tuning
For novice archers and those brand new to archery, when trying to decipher what “tuning your bow” is leads to a lot of confusion and conflicting information that you must wade through. Tuning your bow and sighting in your bow are two different phases that you undertake. Tune first, sight in second.
The tuning phase is a process of checking that all the componentry and systems of your bow are working appropriately, in time, and according to their specifications. Tuning has nothing to do with accuracy. Think of the analogy of building a house. You need to build strong foundations of the house at the beginning to support the later addition of the walls and roof. If you have poor foundation the walls and roof won’t fit perfectly and you have trouble overcoming later problems. The tuning phase ensures that all the “foundation issues” of your bow are correct so as not to later impact during the sighting in phase. Poorly tuned, under tuned, out of tune all mean the same thing and these terms are used interchangeably across the internet.
Problem of trying to sight in a poorly tuned bow
The sighting in phase is the deliberate adjustments made to the bow sights (generally) to achieve accuracy, meaning your arrows are consistently hitting in a small grouping at what you are aiming at. Sighting in occurs AFTER the bow has been tuned. To put more bluntly, the better tuned your bow is, the easier it is to achieve and maintain accuracy.
Trying to sight in your bow whilst naïvely or unwittingly assuming your bow is “in tune” is virtually impossible, confusing, and ever so infuriating. Your sighting in adjustments don’t produce the outcomes normally expected as the hidden tune problems are impacting and you go around and around making your sighting in adjustments but failing to achieve consistent accuracy. What in
actual fact you need to do is go backwards and ensure the bow is well tuned before you commence sighting it in.
One thing affects others
A bow might lose it’s tune over time with reduced accuracy often the most noticeable sign. A simple change of one system on your bow can have a flow on effect that alters the tune. A new bow string will slightly stretch from its original length and potentially alter draw weight, draw length, cam timing, peep sight location, anchor points and arrow rest drop away timing. So you can see one single change might make you revisit the need to re-tune your bow then sight it back in to achieve consistent accuracy. A bow check tune should occur 6 monthly.
What causes a bow to lose its tune
Poor handling and storage, knocking , bumping and dropping the bow.
Replacement / swap over of arrow rest.
Change of nocking point.
Change length of D Loop.
Change of cams.
Bow string or cable string stretch.
Using different length or style of release aid.
Change of draw weight.
Personal fit
A bow that has been properly tuned and sighted in by you will be accurate for you and you only. This is because the bow has been turned and sighted in to meet your body measurements and requirements. The draw length, draw weight, peep sight location and all other adjustments have been done to meet your needs - to the exclusion of all others. Think of the analogy of needing a pair of reading glasses. The optometrist will spend considerable time trialling different lenses to provide you the sharpest focus for your eyes. Anybody else trying on your glasses won’t achieve that same sharp focus as their eyes are totally different from yours. Your bow is the same as those glasses. It meets your specific fit but no one else.
Variety of advice on how to tune your bow
There is volumes of information available on how to tune a compound bow. Archery is a sport of opinions and no one tuning process can claim to be the definitive way to tune a bow. So long as the result is a highly tuned bow, it is valueless to debate which way is better. The following steps undertaken in this order will provide you a highly tuned bow.
1. CHECK/SET DRAW LENGTH
Check/adjust the bow to meet your proper draw length. Often you need to adjust the cams to get to your draw length, or swap over to another set of cams to achieve your draw length. Any movement or changeover of the cams has to be done using a bow press to take the tension off the limbs. If after moving or swapping over cams you still cannot achieve your required draw length, it is valueless to proceed further as correct draw length is the first and most important requirement of the bow.
2. SET DRAW WEIGHT
Mark both tiller bolts with a pencil. These bolts hold the upper and lower limbs to the riser.
Screwing in the tiller bolts all the way will produce the maximum draw weight that the bow can deliver. Note how many turns it took to screw fully in. Then back out both upper and lower tiler bolts the exact same number of turns. The further you wind out the tiller bolts the lower the draw weight will be. DO NOT fully screw out the tiller bolts or the limbs will disconnect from the riser. Both tiller bolts must be wound out the exact same number of turns to ensure both limbs deliver equal energy. If the limbs are set differently, this mismatch will cause issues later as the limbs will deliver uneven energy at different speed impacting accuracy and shot consistency. Set your appropriate draw weight by using a bow scale drawing the bow string back to your anchor point. Excessive physical straining, sky drawing or bending your body in order to fully drawn back means you have set the draw weight too heavy. It is better to have a lighter draw weight to begin to avoid shooting fatigue and resultant poor form.
3. CHECK AXEL to AXEL DISTANCE
Check the cam axel to cam axel distance according to manufacturer’s specifications. The
axel-to-axel distance should not vary by more than 1/8 th inch (3mm) outside the
manufacture’s specification. Example…If the bow states it is a 32inch bow then the axel-to-
axel distance should not be more than 1/8 th of an inch greater or less than 32 inches. To
change axel to axel length you need to lengthen or shorten the bow cables depending if the
axel to axel measurement is under or over length. The adjustment can only be done when
the bow is in a bow press with the tension taken off the limbs. Perform small adjustments
via half or one full turn at a time and re-measure. At this step it is important that you
perform the same adjustment on both cables. Example... If you add a single turn to one
cable then you must add a single turn to the other cable as well. Adding turns shortens the
cables thus will shorten the axel to axel length. Removing a turn will do the opposite and
lengthen the axel to axel length.
4. CHECK THE BRACE HEIGHT
Check the brace height according to manufacturer’s specifications. Brace height is
measured using a bow square from the bowstring to the deepest part of the grip which is
commonly called the pivot point. Commonly the deepest part of the grip is in line with the
Berger hole in the riser. The Berger hole is the hole that the arrow rest gets screwed into.
Simply clip the bow square onto the bow string and measure the distance from the bow
string to the centre of the Berger hole. Brace height impacts the speed of the arrow. A
smaller brace height means the bow string is closer to the riser so the arrow stays on the
string longer and absorbs more kinetic energy gaining more acceleration. A higher brace
height means the arrow comes off the string earlier absorbing less kinetic energy thereby
less arrow speed. A higher brace height in theory provides a more forgiving bow as the
arrow spends less time on the bow string thereby having less opportunity for the arrow to
be influenced by the string. To change brace height of a compound requires a bow press to
either add or subtract twists in the bow string. Recurve bows are more susceptible to
change of brace height due to the constant stringing and unstringing of the bow. Brace
height is less important for compound bows and staying near the manufacturer’s
specifications will generally be sufficient.
5. CHECK CAM TIMING
Modern compounds will have a mark, hole or small indentation on the edge of the cam that aligns under the bow string to indicate proper cam timing, however a much better way of checking cam timing requires a second person to watch you draw the bow back to full draw. Both cams must roll of peak weight at the same time with both cams touching their draw stops at the same time. If the cams are not synchronised together you get “two full draws”.
The first full draw occurs when the first cam rolls over to where it stops but there is more bow string travel to get the second cam to roll over to where it then stops. Cams that are not perfectly timed will produce a harsh draw, a spongy feel at the back wall, erratic arrow flight, loss of arrow speed and lots of bow vibration on release. Out of synch cam timing means your arrow will go high or low and if not identified and corrected at the tuning stage, the problem will be masked and during your sighting in stage, your normal adjustments to fix high or low arrows (ie: by moving nocking point slightly up or down or moving arrow rest up and down) will produce confusing and inconsistent results. Out of synch cam timing requires a bow press to add or reduce twist in the bow cables (not bow string) to either make the one cam reach its back stop slower or faster to match the other cam. Remember it is always better to add twist than to remove twist. Note that adding or removing twist in a cable can have impact on draw length and draw weight.
6. SET NOCKING POINT
The nock point is where the arrow is connected to the bow string. Setting your nocking point can be done different ways. One method is to measure along the bow string between the cam axels and tie or clamp in your nocking point so your arrow is centred exactly mid-way. Another method requires you to put the bow upright in a vice and using a bubble level, ensure that the bow string is perfectly vertical . Ensuring that the bow string remains perfectly vertical, place an arrow on the bow string and run the arrow 90 degrees from the bow string ensuring that the shaft of the arrow is running through the centre of the berger hole (the berger hole is the threaded hole on the riser which the arrow rest is screwed into).
Once satisfied, tie or clamp in your nocking point.
7. SET ARROW REST
Screw in your arrow rest against the riser using the berger hole. If necessary adjust the arrow rest up or down to retain the arrow shaft running through the middle of the berger hole when the arrow is 90deg to the bow string. Next you need to adjust the lateral (left to right) movement of the arrow rest to ensure that the arrow sits exactly in the direction the bow string will be pushing the arrow upon release. If the arrow rest is ajar to the direction of the bow string travel, the arrow will go left or right. Again, like cam timing, if the arrow rest is not perfectly in alignment, later sighting in adjustments will not achieve accuracy.
Nock and arrow and place it in thr arrow rest. Measure the distance between the arrow and the riser at the back and front of the arrow rest. If there is different distance move the arrow rest until the measurement is the same. A better and sure fire way of achieving perfect arrow rest lateral positioning is to use the tiller bolts as reference points. You might have to remove the bow sight to do this. Tape a length of thin fishing line between the two tiller bolts (the bolts that hold the upper and lower limb onto the tiller). Ensure that the fishing line is tight and taped to run perfectly through the middle of each tiller bolt. Next, using an old arrow, nock the arrow into the nocking point on the bow string, and cut this arrow 1 or 2 mm short of the fishing line. With the fishing line tight and the cut arrow nocked and sitting in the arrow rest, move the arrow in behind the fishing line. Move the arrow rest until the fishing line evenly dissects the circumference of the arrow shaft. Don’t throw the cut arrow away but save for next time tuning. Reinstall the bow sight.
HINT: Later on when actually shooting the bow, if you have a drop away arrow rest, ensure that the arrow rest is dropping away prior to the passage of the arrow fletches over the arrow rest. If not dropping out of the way, arrow fletches touching the arrow rest will impact trajectory of the arrow resulting in accuracy issues. Drop away arrow rests usually have markings that align at full draw to indicate correct drop away. Lip stick left on the arrow rest drop away after arrow release which was applied to the outside edges of the arrow fletches prior is a good test to prove correct arrow rest drop away.
8. INSTALL D-LOOP
With the nocking point set and arrow rest installed, tie in your D-Loop
9. CORRECT PEEP SIGHT
Next install or adjust the peep sight. This is best done using a second person. Draw the bow back to full draw and settle into your anchor position and have the second person mark with cotton, string or adhesive tape the approximate location on the bow string where the peep sight is to be installed in front of your dominant eye. If needed. taking the tension off the bow string allowing you to separate the bow string strands as evenly as possible and insert the peep sight roughly where it is supposed to go. With your eyes closed, draw the bow to full draw and settle into your anchor point then open your eyes. The peep sight is in the correct position when your dominant eye is looking through the middle of the peep sight without any head, eye or hand movement. Do the l draw- eye closed/open cycle several times until you are satisfied the peep sight is correctly positioned. Using dental floss or serving, tie off the peep sight to the bow string to stop any movement of the peep sight up or down the bow string. Tying off the peep sight to prevent peep sight movement along the bow string is important as bow string vibration will cause it to move resulting in deteriorating accuracy and inconsistency. If the peep sight is side on, or slightly ajar at full draw, trial and error by twisting the bow string next to the peep sight just prior to drawing which should eradicate this issue. Alternately take the tension off the bow string and transfer two or three individual bow string strands to the opposite side of the peep site. Do this evenly in terms of moving 2-3 stands to the other side of the peep site but also transferring 2-3 strands back to the other side so that there is 50%-50% spread of stands either side of the peep sight. Trial and error until the peep sight properly aligns to the dominant eye each time at full draw and then re-tie off the peep site.
10. CORRECT SPINE SELECTION
Although arrow selection is not part of tuning your bow, it is an important aspect as shooting arrows not suitable to the bow is a waste of time.
To ensure you take advantage of your efforts so far, ensure that you are shooting arrows with the correct “spine” for your bow. Spine is simply the arrows stiffness, the lower the number the stiffer the arrow. As an example a 400 spine arrow is more flexible than a 340 spine arrow. Commercially produced arrows are marked with their spine along the shaft.
Don’t shoot an arrow if you don’t know or can identify its spine. All arrows flex when coming out of the bow before recovering and flying to the target. This flex is called “The Archers Paradox” with lots of info and slow-motion footage on YouTube. Shooting arrows too rigid (over-spined) or too flexible (under-spined) for your bow introduces a variable that produces inconsistency and inaccuracy. Generally, the bigger the draw weight of the bow the stiffer the arrow spine needs to be. Sometimes terms such as quick bow or slow bow is used when discussing arrow spine in terms of arrow speed. Heavy draw weights generally create faster arrow speed and the need for stiffer spine and the reverse for slower bows.
Shooting a significantly under spined arrow on a heavy draw weighted bow can be dangerous and almost akin to dry firing the bow as the arrow cannot fully absorb sufficient kinetic energy the bow imparts into the arrow with the un-absorbed kinetic energy feeding back into the bow as vibration/oscillation, heat and sound. If the kinetic feed back exceeds what the bow can absorb then you can get the effects of a dry fire and potential resultant damage. Using a bow scale to accurately measure the draw weight of the bow is the safest and most accurate way to determine the bow draw weight and thus select the correctly spined arrow for the bow. There are numerous arrow charts on the internet to assist in correct arrow selection.
When talking about arrow necessities, the spine is the one mandatory aspect that must be correct.
Arrow technology and arrow selection can be confusing especially for novice archers and arrow length, grain (weight), diameter, straightness, tip, and arrow material all play a factor to some degree. Regardless, ensure that you shot arrows with the correct spine for your bow. If unsure, corroborate your internet research by advice and guidance from online retailers or visit an archery pro-shop when making arrow selection.
11. NEXT STEP.
You have taken the time to tune your bow and have the correct spined arrows. What next?. At this stage if you have followed steps 1 to 9 you will have created a tuned bow sufficient to achieve consistent, accurate, and predictable sighting in at various distances. For novice archers, it would be appropriate to now sight in the bow as it is more important to be shooting arrows down range to develop proper form and experience.
For the more advanced archer, you may wish to “fine” tune the bow via paper tuning, bare shaft tuning, group tuning or walk-back tuning. Each method of fine-tuning has pros and cons with paper tuning with fletched arrows a good starting point. Using a combination of methods to fine-tune is advantageous and will definitely provide better results in terms of accuracy and consistency when sighting in. There is a wealth of literature on the internet to refer to.