May 31, 2022
By Joe Bell
Question: My bow continues to paper-tune with a tail-left tear. I’ve tried moving my rest to the right, to the left, and I’ve adjusted the string-yoke harnesses as suggested by a friend. But I’m still getting a ragged tear and lousy broadhead flight. Can you help? — Alex D., via e-mail
Answer: Bows that don’t tune easy can be frustrating, and I’ve even had a few that wouldn’t tune at all! However, modern-day bows are manufactured with exceedingly close tolerances, so it’s a matter of making a few small adjustments to solve the problem. It could be as easy as resetting the cams, so they are synchronized and rotating plumb with the bowstring. Or you may have to move one or both cams to a different position along the axle by adding shims (small spacers) to one side of the cam and removing from the other.
Such steps are often referred to as “super-tuning,” but these actions simply place the bow’s powerstroke directly in line with the arrow. Shooting style varies, so although the bow may tune perfectly in a shooting machine, this may not be the case for a particular archer.
To perform these tuning steps, you need to have access to a quality press and some basic archery tools so you can work systematically until the flight issue is cured.
When tuning a bow, don’t skip the basics. With a persistent tear like yours, be sure to first check for fletching contact. Spray aerosol foot-powder across the arrow’s fletching area, then shoot it into a firm backstop. Any “smears” of the white powder indicate vane contact with the rest, cables, or riser — a common culprit of poor arrow flight. Also, don’t tune a bow without using several shafts to see if the tears remain the same. If spine varies from one arrow to the next (trust me, not every arrow is made the same), you’ll see various types of tears. Twisting the nock in one-quarter increments could also produce different tears.
Once the basics are covered, move on to synchronizing the cams. The cables should strike the cable stops at the exact same time. Next, assess each cam’s vertical position while at full draw. Cam lean is checked by using a bow-drawing device (or draw board) to allow an easy evaluation of how the cams are oriented. By laying an arrow across the surface of the cam, you can determine if the cam is in line with the bowstring. If the arrow points off-center to the left or right, then cam lean is present. If a draw board is not available, draw your bow and have a friend assess the cams’ positioning. To fix cam lean, adjust the string-yoke harness by twisting one side and untwisting the other, allowing the limb’s tip to equalize the load.
If the left tear persists, try moving your rest to the right, but oftentimes this only works for a very small left tear. Rest adjustments are better for “micro-tuning” groups downrange and adjusting the points of impact for fieldpoints and broadheads. Overall, it’s better to maintain the proper arrow centershot position as recommended by the bow’s manufacturer. This provides improved vane clearance and allows the arrow to stay in the center of the bow’s riser, limbs, and grip for optimum performance.
With large or persistent tears, shimming one or both cams will eventually eliminate the tear (I prefer to yoke-tune first). When repositioning the cam, always move it in the direction of the tear. Depending on your bow’s spacers, you may have to purchase new shims with varying thicknesses to make the necessary horizontal adjustments. Lancaster Archery and Last Chance Archery sell relatively inexpensive spacer kits and tools for this type of tuning.
There are several ways to tune a bow, but I believe paper-tuning is the most precise way to capture irregularities in arrow flight because it examines flight issues only a few feet from the bow. To improve paper-tuning even more, try using a bare shaft. To simulate the weight of vanes, wrap the rear of the shaft with a piece of electrical tape. The bare shaft will expose the smallest rips in paper so you can improve consistency downrange. Any small accuracy adjustments at this point are resolved by moving the rest or D-loop in 1⁄16" or 3⁄32" increments until maximum accuracy is achieved.