When it comes to getting a new string for your racket, the majority of players who step into my shop with some basic level of confidence in their preferred tension settings. When I tell them that this can be a great number to string with, depending on the type of string they would want to buy and install, things get a bit more confusing. As with the tires and tire pressure on a car, you’d ideally want to first choose your string and then adjust your tension accordingly. So in this article, we’ll be covering the different types of strings for rackets so you have a good idea of what to choose from once you’re in the shop. We’ll also explain the differences in string types for each racket sport.
Strings come in many materials and constructions ranging from a single monofilament to multifilament strings composed of thousands of separate filaments. Strings with more filaments tend to be softer but less durable, whereas a monofilament would be stiffer and more durable. Some strings are constructed with a center core of one to several larger filaments and with one to three layers of wraps around them for durability. Players choose soft strings because they have less shock on impact and a bit more power. Stiffer strings are chosen because they add control and many players like the “feedback” of a “crisper” feedback.
There are four variables in finding the perfect string. These are material, construction, gauge and tension. With these four variables we can make thousands and thousands of combinations. Finding the perfect mix for you as a customer, is a stringer’s job.
There are five general materials used in string construction.
Nylon or synthetic gut
Most players play with nylon strings, or more commonly known as synthetic guts. There are different grades of nylon, with varying levels of feel, so don’t be afraid to try out a few. All in all, synthetic gut delivers a good combination of playability and durability at a great price. In fact, nylon multifilaments offer impressive comfort and power. Unlike the more basic synthetic guts (which have a single, solid core), multifilaments are comprised of hundreds or thousands of ultra pliable, elbow-friendly fibers and are bundled together with flexible resins like poly-urethane.
Back in the day however, almost every tennis player played with natural gut made out of the intestines of cows. It is made with the from the thin stretchy membrane known as the serosa which surrounds the intestine and which allows the intestine to expand and contract as a cow digests its meal. The intestine of a cow is long enough to string a tennis racket, but the serosa is too thin to make even a 0.8 millimeter string. So it takes three cows to make a thick enough string for one tennis racket. The process takes a few days of cleaning, twisting, drying and polishing: that’s why natural gut is so expensive. However, the result is a string that is more elastic than any man-made synthetic, and it holds its tension better than any synthetic. The main problem is that is not as durable and tends to break more easily, especially if it gets wet. It is a string that offers a maximum feel and control due to it’s ultra low stiffness and that’s why some players on the ATP and WTA (and on the lesser known tours) still prefer it.
Since the beginning of the 90’s and the “graphite era” however, it seems that professionals are in less and less need of the soft feel of natural gut because they intent to play almost every ball as hard as they can and this has even become more so the last few years. Therefore, they like to play with polyester because polyester is stiffer than natural gut and is also stiffer than nylon but still gives a lot of control on powerful shots. The incredible stroke speed enabled by polyester also translated into higher levels of spin, which literally changed the trajectories and angles available to players. A lot of manufacturers of polyester strings have begun to develop technologies to create “softer” polyester strings and a few have noticeably done a good job in that regard. Another popular way to play with polyester strings at a comfortable level is to use a so called “hybrid”, a set up where polyester strings are installed in the racket’s main, vertical strings and a softer nylon in the cross, horizontal strings, to create what is commonly known as the “best of both worlds”. Due to it’s high stiffness and relatively low power, polyester is not recommended for beginners or players with arm injuries.
Polyester and tension loss
Polyester has a big downside and that is that is loses tension faster than any other string. Many players say or claim that polyester holds its tension better than nylon, but laboratory tests prove otherwise. If a racket is strung with a nylon string at a tension of 60 pounds, then the tension will have dropped to around 55 pounds by the time the racket arrives on the court. However, because the polyester is so stiff, the strings will feel stiff even when the tension is low. The reason is that the strings stretch a few millimeters when they are used to hit a ball, and hence the tension rises rapidly due to the extra stretch while the ball is on the strings. With natural gut or nylon the rise in tension due to the stretching of the string is smaller, and the feel of the string depends more on the tension before the string starts to stretch.
Kevlar, a Dupont product that has become the generic term for a category of materials known as “aramids” and is still the stiffest string out there. Therefore, it is usually combined with a soft nylon cross. Ultimately, Kevlar hybrids are the least powerful and least comfortable strings currently available. Players trying to Kevlar hybrids for the first time (switching from nylon strings) are recommended to reduce tension by 10% to compensate for the added stiffness. These strings are definitely not recommended for players with arm injuries.
Polyektones or PEEK polymers are a newer class of material used in racket sports strings. Zyex offers low dynamic stiffness that allows it to deform and recover more completely than other synthetic materials. It can also be made to have exceptionally low creep under continuous tension, allowing racket strings to maintain tension and playability longer.
Polyester, co-polyester and nylon strings are extruded as a single strand. Traditional 100% polyester strings typically have higher stiffness values and are best for advanced players seeking maximum control and lots of durability. Co-polyester monofilaments are made with additives to increase elasticity and comfort, though they are still firmer than most nylon based strings. Many of today’s co-polyesters are constructed with low-friction coatings to enhance snapback which increases spin (and reduces breaking your string prematurely due to notching). Poly-based monofilaments are ideal for big hitting intermediate and advanced players who want durability, control and spin.
Solid core with single wrap
Most popular nylon string construction – majority of so-called synthetic gut strings are solid core/single wrap. Main benefits are tension maintenance and crisp feel. Quality of nylon center core, as well as size and orientation of outer wraps can influence the feel and comfort of the string.
Solid core with multiwrap
Provides additional playability and cushioning.
Multicore with multiwrap
Smaller multifilament core with one or more outer multifilament wraps. Offers similar comfort benefits to multifilament strings with added durability.
Bundles of micro synthetic fibers are twisted together, similar to natural gut. Nylon multifilaments are typically more comfortable than solid core strings due to the cushioning effect of hundreds or even thousands of micro fibers. Resultant effect is a soft and comfortable string, recommended for players suffering from arm problems who don’t want to pay the high price for natural gut. Normal use causes multifilament strings to fray, like gut, which can be alarming to players switching from solid core strings. With the exception of braided Kevlar, multifilament strings are generally classified as “soft” strings.
In recent years there has also been a tendency of manufacturers to start producing strings in a series of standard and textured versions of the same string. Textured strings can be found in nylon and polyester, giving all ability levels a way to get a little extra grip on the ball, or so it has been claimed by manufacturers. Nylon or synthetic guts typically derive their texture from an extra filament, raised ridge, on the surface. Polyesters typically derive their texture from a dented or rough surface. In each case these strings provide better friction, which is claimed to be enhancing spin but we’ll dive into that subject in another article.
With the popularity of polyester strings, it is much easier to produce geometrical shaped strings, now available from three sided (triangular) to eight sided (octagonal) strings. The advantage of these strings are the sharp edges made grab the ball better offering more spin, or so it has been claimed by manufacturers. Some of the newer strings have five to eight rounded edges to allow for more snapback on the strings.
Nylon is still the preferred string of most recreational players because it is generally speaking cheaper and more durable than gut and is softer than polyester and Kevlar. As a side note, there is nothing in the rulebook to stop a player from using a steel string if he or she wants to, but it will feel really, really stiff and it will cut the ball to pieces. No seriously, do not mention this to your stringer or expect to be laughed at.
In fact, the International Tennis Federation’s rules don’t say much about strings at all. They state only that
“The hitting surface of the rackets shall be flat and consist of a pattern of crossed strings connected to a frame and alternately interlaced or bonded where they cross; and the stringing pattern shall be generally uniform, and in particular not less dense in the centre than in any other area. The racket shall be designed and strung such that the playing characteristics are identical on both faces.”
The rules go on to state that,
“The strings shall be free of attached objects and protrusions other than those utilised solely and specifically to limit or prevent wear and tear or vibration, and which are reasonable in size and placement for such purposes.”
So don’t worry, you can perfectly install a vibration dampener…