Strings are a very important part of your racket, but to many players they are just an afterthought. Players may spend 6 months testing rackets and 6 minutes choosing a string. Every player has different needs and preferences.
Here are a few guidelines to make your string and tension selection easier:
It's very difficult to obtain consensus on what makes a string playable. Some players like a crisp, firm playing string while others equate playability with softness and comfort. Generally, a playable string is resilient, which means it snaps back quickly upon ball impact. The material, construction, and thickness of a string will all affect the playability of a string. The most resilient (playable) string at this time is still natural gut. This is the only string made from a natural product - beef intestines. It is the oldest tennis string made and remains the benchmark for playability.
Most of us want a string that offers everything. Unfortunately, increased durability in tennis strings is usually at the expense of playability. Thicker gauges and abrasion resistant materials will be more durable, but they are less elastic and resilient than their thinner, nylon-based counterparts.
Generally speaking, thinner strings offer improved playability while thicker strings offer enhanced durability. Thinner strings also provide more spin potential by allowing the strings to embed into the ball more.
Most of today's "performance synthetics"(including synthetic gut) are constructed of nylon, albeit a higher grade than basic nylon string. Today's manufacturing processes produce nylon strings that provide a good combination of playability and durability. Today, 98% of non-professional players use nylon strings.
The ultimate string for playability and feel often overlooked due to its cost. Natural gut is an excellent choice for players with arm problems or those who simply want the best. It remains the #1 string choice for the top 20 ATP tour.
Very durable string designed for string breakers, not much power or feel. Polyester strings also experience rapid initial tension loss. Players switching from a nylon or synthetic gut string should increase tension by 3-5 pounds.
The most durable string available. Kevlar is very stiff and strings up very tight. Therefore, it is usually combined with nylon to reduce the string bed stiffness (Kevlar main strings, nylon cross strings). Players trying kevlar hybrids for the first time (from nylon strings) are recommended to reduce tension by 10% to compensate for the added stiffness.
String tension is the final piece in the racket-string-tension triad. It's also the least understood by most recreational players. Let's start with the basics - lower tensions provide more power, tighter tensions provide more control. This is a very general rule of thumb and assumes a certain level of player ability.
Each racket has a recommended tension range. This range has been determined by the manufacturer as a result of extensive play testing by real players. If a player doesn't have a specific need (more power, arm problems, etc.), he should start at mid-range and make any adjustments from there.
Otherwise, here are some specific guidelines for selecting a string tension.
As we stated above, if a player is seeking more power from his racket, he should try dropping tension a few pounds. The string bed will deflect more (and the ball less), returning greater energy to the ball. There is a point of diminishing returns where the string bed turns into a butterfly net, but it's well below any racket's recommended tension range.
A tighter string bed deflects less and deforms the ball more, providing less energy than looser strings. This means the ball won't fly as far when you hit it. Beginners who are shanking the ball in every direction won't gain any advantage by increasing tension, but intermediate and advanced players who are hitting a lot of long balls will be able to reduce the depth of their shots without changing their swing. It is also generally accepted that spin potential is enhanced with higher tensions, which provides even more control for topspin and slice players.
Lower tensions result in a softer string bed and a larger sweet spot, reducing the amount of shock and vibration transmitted to the hand and elbow.
Whether changing head sizes or brands, you will need to make the corresponding tension change. If 60 pounds was mid-range on the old racket and the new racket's tension range is 50-60 pounds you should start at 55 pounds with the new racket.
If a player changes from a standard nylon or synthetic gut string to a kevlar composite or hybrid, we suggest he reduce tension to compensate for the added material stiffness. With composites, we recommend a 5% reduction. Kevlar hybrids should be strung 10% looser to approximate the same feel of nylon strings. On the other end of the spectrum, players switching from nylon strings to polyester may want to increase tension 5-10% to compensate for polyester's high initial tension loss.