Tuning a Bow: Part 1

Tuning a bow doesn’t have to be a complex issue. In fact, knowing how to properly care for your equipment will ensure it lasts for many years. Before each hunting season, it’s best to inspect your rig to be sure everything is in working order. This is the first of a two-part series where we lay out everything you need to know in order to do so. You don’t need fancy tools, just a bit of time and some elbow grease.

Inspect Bow String and Cable

The most vulnerable parts of the bow are the strings and cables. When drawn, they are under tremendous tension and over time the string will stretch and weaken, which causes alignment issues with cams, nocking points and peep sights. It is also extremely dangerous to continue shooting a frayed string. A string breaking while you are drawing back or at full-draw is a recipe for injury and a damaged bow. To determine if you need a new string check for these signs:

- The string is fraying or there are cut/loose strands.

- String and cable serving is separating at the cams leaving the bowstring unprotected (if you see indications of this, it does not mean you need a new string, but you should have the string re-served).

- Your peep sight has rotated out of alignment. This is an indication of the string stretching.

- Your bows axle-to-axle length and brace height has changed. Use a tape measure and measure from axle to axle with the limb bolts tightened to the max. Also, measure the brace height from the center of the Berger Button (where the rest screws into) in the riser to the string. If the bow is out of factory specifications due to string stretch, your measurements of axle-to-axle will be longer and the brace height will be shorter.

- Depending on the amount of use, most strings last three to four years before needing to be replaced. If you replace your bowstring, shoot 50 to 60 times to allow it to settle before moving on to the next step of the tuning process.

Check your bow string for any signs that it may need to be replaced before hunting season.
Check your bow string for any signs that it may need to be replaced before hunting season.

Check for Cam Rotation

If you determined that your string does not need to be replaced, there is still a possibility that the string has stretched. Even a small amount can cause the cam(s) to rotate and disrupt the timing. Cam rotation will also shift your peep sight alignment and nocking point. This is a big cause of poor broadhead flight, but it can be fixed by twisting the string to create more tension on the limbs and cams. If you have the tools, you can fix these issues yourself. However, taking your bow to a reputable pro shop where a technician can get your rig back to factory specifications is recommended.

Before you take your bow to the shop, here are some observations you can make at home to determine if you cams are not properly tuned due to string stretch:

1. Your peep sight has rotated out of alignment.

2. Your bows axle-to-axle length and brace height has changed.

Find the Center Shot

There are several ways to find the center shot, such as laser tools or bow squares to line up the nocking point and arrow rest. Other methods include eyeballing the string and making adjustments when paper tuning.

When tuning a bow, you should find the center shot and ensure yours is aligned properly, which will result in accurate shots.
When tuning a bow, you should find the center shot and ensure yours is aligned properly, which will result in accurate shots.

To find the center shot, get two one-inch sections of tubing that is the same diameter as your arrows. Or, cut sections of an arrow that is the same diameter of the arrow you will be using. Get two Allen wrenches that will fit the limb bolts of your bow and slide a section of the arrow (or tubing) over the Allen wrench.  Place the Allen wrenches into the limb bolts and use a rubber band to stretch between the two limbs, and place it around each of the sections on the Allen wrenches. Put an arrow through the two sides of the rubber band and nock it on your string. Loosen the adjustment bolt on your rest and move it left or right until the rubber band is lining up with the arrow on both sides, then tighten the adjustment bolt. Since the diameter of the space between the stretched rubber band is the same as the arrow you will be using, you will find the exact center shot. You will need to walk back or paper tune so you can fine-tune the center shot location to your release form.

Installing and Aligning a Peep Sight

A misaligned peep sight can interfere with your shooting form. When a bowhunter sets up to make a shot, all the mechanics should feel like second nature. If you have to alter your anchor point to look through the peep sight, it needs to be adjusted. Below is a video that shows the proper way to install and align a peep sight.

Steps for perfect Peep Sight Alignment:

1. Use a string spreader to split the bowstring perfectly in half. If your string is two colors, its strands are typically divided evenly among the different colors.

2. Install the peep sight by inserting the strands of strings into the grooves of the peep sight.

3. Tie a few half hitch knots using dental floss or bowstring material. This is a temporary knot that will allow for easy peep adjustment until you find exactly where the peep needs to be permanently anchored.

4. To fit the peep’s location to your form and anchor spot, draw your bow back. Once you are at full-draw, close your eyes and anchor the string as you normally would. Then open your eyes. You should be looking right through the peep sight. If not, adjust it accordingly and repeat this step until it is perfectly aligned with your line of sight.

Selecting the Best Arrow Shaft

People spend a lot of time and money to pick the best bow, but hunting arrow selection is often an afterthought. Here is a guide to picking the right arrow so your bow can perform to its maximum capabilities. The proper arrow selection process takes arrow length, bow poundage and application into account.

Spine is simply a measurement of an arrow’s stiffness – the lower the number the stiffer the arrow. Hunting retailers and even some manufacturers will provide customers with a static spine chart, which shows how much an arrow bends when unchanging pressure is applied. The problem is, when you release an arrow, the thrust of the string will cause it to bend. How fast the arrow reacts is called dynamic spine. There are considerations other than bow poundage and arrow length that will determine your dynamic spine. To calculate, you need to determine your adjusted bow draw weight before consulting the spine selection chart.

Arrow weight is measured in grains per inch (gpi). A lighter arrow flies flatter and faster. But they  are also unforgiving and unable to absorb the energy of a higher pound draw weight and require a perfectly tuned bow and proper shooting form for consistent results. On the end of the spectrum, heavier arrows deliver more kinetic energy and are more forgiving upon faulty releases.