Bow Tuning 101

February 19, 2009 by admin

By Andrew Gegelman

For most bow hunters, tuning their bow means being able to hit what they are aiming at. And for others they just hope their bow will become tuned by itself. But they are wrong. Tuning your bow now might mean the difference between trophy and tragedy.

First things first, you should not attempt to tune your bow if it has just been purchased, (new) or you have had a new string and cable put on. The string and cable will stretch, and the quality of components will depict on the amount of stretch that will occur. Most strings that bow manufacturers put on will eventually stretch to the point that they are not very accurate. The string and cable can stretch many inches, it does not happen all at once but you will know when it has stretched out of tolerance. I just recently had the string and cable on my bow replaced, after I had trouble with inconsistently flying arrows (it had to be in a 3-D tournament). Needless to say my score was just slightly below average and my confidence and pride was injured.

Once we have gotten our bowstring and cable broken in, we can look at some arrows. Most manufacturers have arrow charts where arrow lengths, draw weight, draw length, and point weight are taken into account. These charts are a good place to start, and find your arrow size. One thing to keep in mind if you shoot a release is that there is very little bend on the arrow when compared to shooting fingers; this gives the release shooter the advantage of shooting virtually any arrow. Even if the arrow is over or under spined the bow could tune without a problem, but if not you might want to select a different weight arrow.

After we have our arrows cut and put together we start with the tiller. The tiller is normally measured from the point where the limb meets the riser out to the string. Either measure with a ruler or a string. Measure the top and bottom of the riser. If the measurements don’t equal each other, adjust the tiller by tightening or loosening one limb bolt or the other until the tillers match exactly.

Next make sure your nocking point and rest are adjusted properly. Adjust the rest so the center of the arrow’s shaft goes through the center to upper 1/3 of the hole where the rest attaches to the bow. Then crimp the nocking point on the string or tie your string loop but not too tight so you can’t move it. Then use a level on the arrow to make sure that it is level with the sight window. Next is to check your center shot. The center shot on most bows should be between center and 3/16” to the left of center for a right handed bow. To find the center shot, take a piece of masking tape and place it just above where the limb meets the riser. Measure the limb and place a small mark at the center of the limb. Make another mark 3/16” inch to the left of center, and then do the same for the next limb. With the arrow on the rest, line up your string along the marks. When the string is aligned with the marks it should bisect the center of the arrow shaft if it does not adjust your rest accordingly.

Peep sights are one of the easiest but most overlooked aspects of bow tuning. With the peep in the string but not tied into place, nock an arrow and draw your bow with your eyes closed. When you open your eyes you should be able to see through the peep without moving your anchor or the bow, if not adjust until you can.

Now we are ready to tune your bow. The first step is to make sure there is no contact of your fletching to either your rest or riser. The best way to do this is a powder test. Spray the back six or seven inches of the arrow, and also spray the rest and the shelf. Shoot your arrow at a target and carefully remove it for inspection. Check the shelf and rest. If any new marks have shown up you are getting contact from your fletching. Depending on where the marks in the powder are depends on what you should do to correct this. If the marks are on the rest, or in contact with your fletching, rotate your nock to eliminate contact with your rest. If there is contact with the shelf, change the spring tension on your rest then repeat.

Next is paper tuning. Paper tuning makes it easy to see what the arrow is doing when it leaves your bow. Set up a piece of paper about six feet away and shoot through it into a solid target. If there is a clean hole, the diameter of the arrow with three tears where the vanes went through. Shoot the same arrow a few times to check your consistency. If the tear is vertical or at an angle, adjust the nock height. If the point of the arrow went through lower than the nock end, lower the nock or raise the arrow rest. If the tear is to the side adjust your arrow rest the direction of the tear until you get bullet holes. Once you are shooting bullet holes, step back a few feet and try it again. If it is good there your arrow is traveling straight.

The last thing you need to do is group tune your bow. After you sight in your bow, go to your maximum accurate range, shoot a group and note any shots that were just poor shots, caused by you. Next shoot another group, but back your top limb off ¼ turn then see if your groups get better or worse. Repeat until you reach one full turn. Then return the top limb to zero and repeat the test for the bottom limb, using a different paper target. Once you have completed this, set your bow to the tiller measurement that grouped the best overall and adjust your sights to the new setting.

With some patience and a little effort, you can eliminate any thoughts of missing the buck of a lifetime due to a poorly tuned bow.