Roberto Gazzara | January 23 2019

String stiffness and String weight vs. strung racquet swing weight

String stiffness

String weight vs. strung racquet swing weight: playability and performance implications

#weservetennis lesson

A quick string lesson from Roberto Gazzara about  two key points to understand how to maximize the benefit of the string choice on a frame.

String stiffness

We always talk about the stiffness of a string. No need to repeat how important is to use a stiffness in line with the player capacity and level of fitness. Hard polyester is for no more than 5% of the tennis population. Not enough muscle power and not perfect timing with a hard polyester will result with extra arm fatigue in the short term and damages in the long term.

Sunny core is the softest string on the market, perfect fit for players searching for comfort and power support.

White beam, with its unique blend with elastomer, is the most arm friendly monofilament in the market making it the perfect allround string for 70% of the tennis population. It is the 21st century version of the syngut!

Black Beam is our high performing stiff monofilament I would suggest only to a few, yet it is not 100% polyester and that makes it better on the arm than most of our competitors polyesters.


String material density – weight

The swingweight of STRUNG racquets is key to the performance and feeling of a racquet.

In fact more and more tennis players tend to customize their racquet, adding few gram to tune the racquet inertias ( swing weight and polar moment to mention the two most important ones).

There is a key factor that almost NO one takes into consideration: the added weight and inertia of the strings:  

Average Density of polypropylene is 0.9 g/cm3, nylon is 1.15 g/cm3 and polyester is 1.3 g/cm3

The weight of a string set of SC is 15g, WB is 20.4g  and BB is 21.7g

On a racquet the AVERAGE added string weight and swing weight are going to be (+/-1.5g; +/- 3 kg*m2)

·         SC w= + 10g ; sw= + 20 kg*m2

·         WB w= +14g; sw = + 25 kg*m2

·         BB  w= +16g; sw = +28 kg*m2

Sunny Core, being the only one ( with few other editions from Isospeed) on the market made of polypropylene, is lighter than any other multifilament string on the market




Roberto Gazzara



Roberto Gazzara | March 19 2021


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