Tension
The string tension of a racquet, usually expressed in pounds, indicates the pressure under which the strings are secured to the frame. String tensions may relate to different playing styles, such as the “feel” of the ball, control over the ball, as well as maximizing power.
Stringing at higher tensions generally offer more control, whilst a lower tension generally increase power and minimises the control and feel on the ball. Lower tensions have a larger sweet spot, provides more comfort and presents more of a trampoline effect thus ensuring greater power with less control. This is caused by the ball on the strings slightly longer due to the cushioning upon contact.
However, having said this, there are exceptions to the rule and in several cases, your customer will already know the type of string and also the tension they prefer.
Beyond all of this, the tension can also impact other factors. For instance, the power player with a tightly strung racquet may quickly tire the arm, possibly resulting in tennis elbow. (please note that other factors including the players technique may impact this scenario too)
String tension has a profound effect on the way a racquet performs and feels too.
You will notice that generally thinner strings will feel tighter than thicker strings when strung at the same tension.
Loss of tension occurs more in the first few sets (about 10%) and then steadily drops an additional 5% by approximately the 12th set on average.
Many professional stringers advise players to string racquets with the lowest tension possible while still being able to maintain control of the ball. Beginning players trying to find their tension should start in the middle of the recommended tension range and adjust the tension from there to meet their needs.
Recommended tensions are usually printed on modern racquets these days making the job of the stringer a little easier.
Gauge
The “gauge” number determines the thickness of the string.
The higher the gauge number, the thinner the string.
The lower the gauge number, the thicker the string.
Thinner gauges offer more resiliency (often equated with “feel”).
Thicker strings last longer. Thick, 15 gauge strings are generally used in beginner and some intermediate racquets.
Most serious players who don’t like to restring too often use 16 gauge.
17 and 18 gauge are for those who can afford string luxury.
Each gauge has a light (L) variation that’s a little thinner.
The rule that the thinner string gives more control and no loss of power is correct.
Commonly strings come in either 16 gauge or the thinner 17 gauge.
Some strings are available in thick 15 (usually in cheap pre-strung frames).
The gauge is for the string under tension.
Gauge diam-mm
14 1.50-1.65
15 1.41-1.49
15L 1.33-1.41
16 1.26-1.34
17 1.16-1.25
18 1.06-1.16
19 0.90-10.5
Resiliency
Resiliency is a commonly used term to describe string responsiveness.
A very important trait often asked about strings is their resiliency.
This is how much they stretch when hit and how fast they recover.
Similar to elasticity, a more resilient string is more responsive or lively, providing greater ball speed or power.
Specifically, resilience is the speed at which a string returns to their original position after contacting the ball.
A high resiliency string (premium multi-filament or natural gut) gives both more power and more control.
As strings age, they lose resiliency and you have to restring.
When this happens the strings lose their resilience, returning less energy to the ball.
This loss of resilience causes the strings to play “dead”.
This is subtle and you cannot really feel it. But the continual shock to your arm is another cause of tennis elbow.
Terminology
Mains – are the vertical strings in the racquet
Crosses – are the horizontal strings in the racquet
Resilience – the ability of a string to recover and return to its original shape after contacting the ball. Over time and through use, strings will lose resilience
Multifilament string – these are strings, usually synthetic made up of various filaments.
Hybrid – the use of two types of strings in the one racquet allowing the use of differing characteristics in a string. For example a string designed for power can be used with a string ideally for durability.
Burning / Wear – Is a cause of breakage earlier than expected. It is caused when a string is pulled too quickly across another string.