You should inspect your bow string frequently for warning signs to watch for that will let you know when its time to get those bow strings and/or cables replaced. This applies to compound bow string replacement, crossbow string replacement, recurve and longbow string replacement. Crossbows are usually tougher on bow strings and cables but this will serve as a good guide.
When you inspect your first bow string, watch for fuzzing on the bow string or cables. Light fuzzing is nothing to get overly concerned about as this is normal wear. As time goes on the fuzzing may get worse and is the most common sign that its time to start thinking about some new bow strings. Watch for this in wear areas like where the cables pass through the cable slide or below the center serving where a lot of archers will rub the bow string with their arm.
One of the most important checks for bow string inspection is to always keep a close eye for broken strands. Many times broken strands will happen under the center serving where the arrow nocks. The constant on/off from nocks will break this down over time and you usually have no idea since it is covered with serving. The wear areas mentioned above are spots to watch as well. Any time you find a broken strand you want to stop shooting. A broken strand in a bow string or cable can be a very dangerous thing and cause catastrophic damage. If a bow string or cable breaks it can not only launch an arrow in any direction but it can cause serious damage to you or your bow.
If you have a peep sight and notice that your peep sight has started to twist when drawing your bow back then your bow string has more than likely stretched. When the bow string stretched it has thrown off the twist rate of the bow string and is causing the rotation. Many times the servings on the bow string or cable will start to separate as a result of stretch. As they stretch the serving slides at the same time causing the gaps.
Another warning sign, but one that a bow string inspection might not immediately find is if you've noticed a loss in performance from your bow. Your bow used to feel powerful and really zip the arrows down range. It seemed to really bury the arrows into the target but now they seem to only be going in half as far. You check your poundage and your 70 pound bow is now only pulling 64 pounds. After checking your axle to axle measurement you realize that it is now 3/8" out of spec. How in the world did this happen? Once again this is a result of a bow string and cables that have stretched over time but may not show the obvious warning signs listed above.
Waxing your bow string is an essential part of bow maintenance and knowing how to wax a bow string properly is as critical as the wax itself. This applies to all types of bows including compounds, crossbows, recurve and longbows. Waxing your bow string will extend the life of your bow string by keeping it from becoming frayed, damaged by dirt or water and will help to keep the strands from becoming dried out and less flexible. Waxing your bow string is very simple to do and only takes a couple minutes of time. Here is a quick rundown on how to wax a bow string.
The first thing is to make sure that your bow string is clear of any dirt or debris. This can be done by wiping with a clean dry cloth. Another little trick is to take a scrap piece of bow string serving material. If you do a half wrap with the bow string serving and lightly pull it down the bow string you will see dirt and old wax being removed.
Next you want to take your tube of bow string wax and rub it up and down on your bow string. A brand I am particularly fond of is called String Snot. Terrible name, but it really absorbs nicely into the strings. You want to make sure the bow string wax is sticking far enough out of the tube that the tube itself is not contacting your bow string. Letting the tube rub on the bow string will cause premature wear. You want to apply a good amount wax but be careful not to overdo it. Ideally you want to make sure the bow string wax covers the bow string with a thin coat. While doing this you only want to wax the exposed portion of the bow string. You want to make sure that you do not wax any of the bow string servings.
Now that your bow string has wax on it, you want to take your finger and thumb and just rub the wax into the bow string. The heat and friction will cause the bow string wax to melt and make it easier for the wax to penetrate each individual strand and cover the entire bow string. I have heard some people recommend the use of a piece of leather instead of your fingers but I believe that you can build up quite a bit more heat with leather. By using your fingers you will not add excess heat to your bow string which could contribute to premature wear. If your fingers get hot you will stop and your bow string will thank you.
Once all of the wax has been rubbed in, you can take the cloth you started with and wipe off any excess wax that might have built up. This will usually be where the bow string meets the servings. By keeping your bow string waxed it will last longer and perform better. It's a great idea to regularly wax your bow string. How often will depend on how much you shoot your bow and the age of your bow string. In general the more you shoot and the older your bow string is the more you will need to keep it waxed.
You will need a serving jig or tool (Letter A in picture to the right below) to replace a center serving on your bowstring. Of course to go with the serving tool, we need the center serving, one of the best sellers is the BCY #62 Braided Serving in .021 diameter. (Letter B in the Picture) Another tool available that makes this operation easier if you are reserving a compound bow is a Cable Separator. (Letter C in the Picture) It makes enough room between your string and cables for the server to easily be spun around your bowstring.
Note: Do this exercise a few times on a "free" area of your bowstring until you are confident with the techniques. Once you have learned how to do this properly, you will be able to replace the center serving of your bowstring or "serve-in" anything on your bowstring.
Start off with a serving tool loaded with serving material. Pull-out about 8 or so inches of serving material to begin and place about two inches of it along the bow string where you want to start your center serving. Then hand-wrap (holding the serving jig or tool) the serving around the bowstring and the two inches of serving you laid on the bowstring, do this five or six times wrapping the serving down the bow string towards the bottom limb.
Then hand-wrap (holding the serving jig or tool) the serving around the bowstring and the two inches of serving you laid on the bowstring, do this five or six times wrapping the serving down the bow string towards the bottom limb. Now using the serving jig or tool (not hand-wrapping) wind the serving back tight into the serving jig or tool till it is tight to the bow string and continue wrapping the serving around the bow string, the serving tool will keep the serving tight and wrapped at the same tension. Once you have wrapped the serving down the bowstring as far as you would like your center serving to be (most manufacturers will serve the center serving on their bow strings between 5-1/2" to 7-1/2") you can now "end" the serving.
Ending the serving is achieved by holding the serving wraps you have just completed tight and pulling about 9 extra inches or so of serving out of the serving jig or tool and then cut the serving were it comes out of the jig or tool (you can now lay down the serving jig or tool. You should now be holding the serving you have completed keeping it tight and have a 9" or so "tail" of serving remaining.) Keeping all the serving you have already completed tight start about 2 inches down the string away from the already completed serving, leave a large "drop" of serving, wrap the loose end of the serving :tail" around the bow string back towards the already wrapped serving, keeping your windings inside the "drop" of serving going in the same clockwise or counter-clockwise direction that you have been wrapping the serving. When you have wound the serving 5 or 6 times, hold the loose end of serving material firm over the already served area. Then begin winding the large "drop" of serving around the bow string and the loose end you have been holding firm, you will continue to wrap the serving while unwrapping the far end. When you unwrap all that can be unwrapped, pull the loose-end you have been holding firm until all slack is pulled out, pull it pretty hard but not so hard as to break the serving, this will tighten the end of your serving on the bow string, cut off the excess serving that is left and then either put a dab of glue over the spot or burn-off the end creating a "burn-ball" that will hold the serving tight and in-place.