Category Archives: True Tension
Yonex Muse 100
We worked on the Yonex MUSE 100 today. Yonex presents the MUSE family as a way to make rallies more comfortable and enjoyable, and the MUSE 100 is one of the few Yonex racquets made in China. Its familiar Yonex isometric head sits on a frame that, at first glance, reminds me of the old “game improvement” category. The Muse 100 looks bulkier than it is, maybe due to the color.
That Game Improvement label deserves a closer look. Many earlier game improvement racquets were light and stiff, with enough weight toward the head to help the racquet move through the ball. They were often marketed to beginners, though that didn’t always make them a good choice for a beginner. The Muse 100 is different.
The MUSE 100 raises a different question: how easy is it to swing in play? Our measurements will help answer that. The HEAD Squared provides a useful comparison. The Head Squared swingweight is about 290, giving us considerable room to add weight for a player who wants more stability. The MUSE 100 we measured is higher, offering less room for that particular modification. That doesn’t make either racquet better for everyone; it just makes the starting point especially important.
The Muse 100, and we’ll show this in the numbers later on, as we will have some pictures up as well, is a heavier racket. I think you can look at the numbers in a minute, but the swing weight is right around 310 or something. For example, the Head Squared is a 290 beginning swing weight. We think it needs to be a little higher, to be honest, but the point is that the Head Squared lends itself to modification for a higher-level player, I believe, more than the Yonex Muse 100.
The Muse 100 is very flexible, as you will see by the numbers, which is good for increased string bed stiffness while keeping effective stiffness down.
Look at the numbers, then look at the racquet. There is also a Muse 98!
| Manufacturer | Yonex |
|---|---|
| Racquet Model | Muse 100 |
| Reference Tension | 54 |
| String | MonoGut ZX Pro |
| Machine Used | True Tension Pro |
| String Bed Stiffness - RDC/Units | 52 |
| String Bed Stiffness -FlexFour/Pounds | 60.0 |
| String Bed Stiffness - SBS/Pounds | 29.9 |
| String Bed Stiffness - ERT/Kg/cm | 35 |
| Racquet Flex, RDC/Units | 54 |
| Racquet Flex, FlexFour/Lbs | 29.9 |
| Racquet - In Plane Stiffness/Lbs/Inch | 409.6 |
| Weight, Grams | 321 |
| Weight, Ounces | 11.32 |
| Balance, mm | 325 |
| Balance, Inch | 12.80 |
| Length, Cm | 68.6 |
| Length, Inch | 27.008 |
| Head Width | 9.68 |
| Head Length | 12.63 |
| Head Area, cm2 | 619.2 |
| Head Area, Sq. Inch | 96 |
| Beam Height @ Grip, mm | 23 |
| Beam Height @ Mid, mm | 25.0 |
| Beam Height @ Tip | 25.2 |
| Beam Width @ Grip, mm | 16.7 |
| Beam Width @ Throat, mm | 14.7 |
| Beam Width @ Mid, mm | 12.4 |
| Beam Width @ Tip, mm | 14.2 w/Bumper Guard |
| Number of Main Strings | 16 |
| Number of Cross Strings | 18 |
| Ratio | .681 |
| Main String Grid Inch/mm | 7.25/184.5 |
| Cross String Grid Inch/mm | 9.13/231.9 |
| Density (% of head filled w/ string) | .699 |
| Average Cross String Space | .514 |
| Average Main String Space | .453 |
| Dynamic Tension, Kp, ERT | 35 |
| Dynamic Tension, Lbs/in | 195.7 |
| First Moment, Nm | .804 |
| Polar Moment | 324 |
| Torsional Stability | 14 |
| Swing Weight, Kg/cm2 | 310 |
| Swing Weight, Ounces | 10.93 |
| Swing Weight Calculated | 339.1 |
| Power, RDC | 40 |
| Control, RDC | 62 |
| Manueverability, RDC | 80 |
| Power, Calculated | 1622.8 |
| Head Points | 5.67 |
| Head Weight, % | 47.0% |
| Center of Percussion | 20.8 |
| Dwell Time, ms | 6.49 |
| Efective Stiffness - lbs | 19.96 (Flex Four Data) |
| K, Lb/In | 166.7 |
| Dynamic Stiffness/Lbs | 294.6 |
| Dynamic Force/Lbs | 126.7 |
| GDR Ratio: static/dynamic | 1.53 |
| Recoil Weight | 149.8 |
| Twist Weight | 225.1 |
| End Weight | 128.5 |
| Tip Weight | 192.2 |
| 9 O'Clock | 99.1 |
| 3 O'Clock | 97.0 |
| Butt End | 1249 |
| COF, Main | .356 |
| COF, Cross | .277 |
Tecnifibre Fire 300
The Tecnifibre Fire 300 is another great surprise from Tecnifibre.
Why a surprise? This racquet shows up as a very stiff racquet both “out of plane and in plane”, as you will see in the following numbers.
However, the string pattern and spacing present a “canvas” on which you can create the string bed stiffness of your dreams!
Given the stiffness properties of this racquet, we wanted to test the “limits,” so we used a reference tension of 54, one less than the suggested 55 maximum. Without going through all of the numbers, I can tell you that the Effective Stiffness is 26.7, which is well below our observed pain threshold of 30.0.
All of our demo racquets are strung with MonoGut ZX Pro (PEEK). What you do in terms of string may change that number, but you can be sure the racquet stiffness can be mitigated by your choice of string, tension, and racquet technician.
| Manufacturer | Tecnifibre |
|---|---|
| Racquet Model | Fire 300 |
| Reference Tension | 54 |
| String | MonoGut ZX Pro |
| Machine Used | True Tension Pro |
| String Bed Stiffness - RDC/Units | 45.9 |
| String Bed Stiffness -FlexFour/Pounds | 61.1 |
| String Bed Stiffness - SBS/Pounds | 46 |
| String Bed Stiffness - ERT/Kg/cm | 33 |
| Racquet Flex, RDC/Units | 73 |
| Racquet Flex, FlexFour/Lbs | 46 |
| Racquet - In Plane Stiffness/Lbs/Inch | 537.2 |
| Weight, Grams | 324 |
| Weight, Ounces | 11.3 |
| Balance, mm | 323 |
| Balance, Inch | 12.72 |
| Length, Cm | 68.7 |
| Length, Inch | 27.047 |
| Head Width | 9.98 |
| Head Length | 12.72 |
| Head Area, cm2 | 643.2 |
| Head Area, Sq. Inch | 99.7 |
| Beam Height @ Grip, mm | 25 |
| Beam Height @ Mid, mm | 25.3 |
| Beam Height @ Tip | 24.8 |
| Beam Width @ Grip, mm | 15.5 |
| Beam Width @ Throat, mm | 13.8 |
| Beam Width @ Mid, mm | 11.2 |
| Beam Width @ Tip, mm | 12.2 w/Bumper Guard |
| Number of Main Strings | 16 |
| Number of Cross Strings | 19 |
| Ratio | .661 |
| Main String Grid Inch/mm | 8.18/207.7 |
| Cross String Grid Inch/mm | 9.87/250.7 |
| Density (% of head filled w/ string) | .794 |
| Average Cross String Space | .513 |
| Average Main String Space | .508 |
| Dynamic Tension, Kp, ERT | 33 |
| Dynamic Tension, Lbs/in | 185.6 |
| First Moment, Nm | .804 |
| Polar Moment | 335 |
| Torsional Stability | 15 |
| Swing Weight, Kg/cm2 | 320 |
| Swing Weight, Ounces | 11.29 |
| Swing Weight Calculated | 338 |
| Power, RDC | 65 |
| Control, RDC | 32 |
| Manueverability, RDC | 73 |
| Power, Calculated | 2352.1 |
| Head Points | 6.46 |
| Head Weight, % | 47.0% |
| Center of Percussion | 21.4 |
| Dwell Time, ms | 7.22 |
| Efective Stiffness - lbs | 26.2 - Flex Four Data |
| K, Lb/In | 134.6 |
| Dynamic Stiffness/Lbs | 369.5 |
| Dynamic Force/Lbs | 141.8 |
| GDR Ratio: static/dynamic | 1.94 |
| Recoil Weight | 161.2 |
| Twist Weight | 240.6 |
| End Weight | 130.9 |
| Tip Weight | 190.3 |
| 9 O'Clock | 97.1 |
| 3 O'Clock | 96.2 |
| Butt End | 129.9 |
| COF, Main | .350 |
| COF, Cross | .262 |
Wilson Defyer Pro 98 v1.0
The Wilson Defyer product release is one of the most unusual and talked-about releases in a long time!
The initial prototypes were “Python”; the next iteration was “Redline”; and the newly released, and final, version is the “Defyer”.
The Defyer is available in 98 and 100 square inch head sizes. The string pattern is 16×20 with spacing that allows for a broad range of string bed stiffnesses to suit most play styles.
The head shape and geometry are familiar; however, there is some “sculpting” going on that adds something to the overall appearance.
While appearance is important, the real stuff is in the numbers, and we have those right here…
After you go through the numbers, stick around for some additional highlights that may go unnoticed.
| Manufacturer | Wilson |
|---|---|
| Racquet Model | Defyer Pro 98 v1 |
| Reference Tension | 56 |
| String | MonoGut ZX Pro |
| Machine Used | True Tension Pro |
| String Bed Stiffness - RDC | 47 |
| String Bed Stiffness -FlexFour | 61 |
| Strig Bed Stiffness - SBS | 51.7 |
| String Bed Stiffness - ERT | 33 |
| Racquet Flex, RDC | 65 |
| Racquet Flex, FlexFour | 51.5 |
| Racquet - In Plane Stiffness | 474.4 |
| Weight, Grams | 325 |
| Weight, Ounces | 11.46 |
| Balance, mm | 327 |
| Balance, Inch | 12.87 |
| Length, Cm | 68.7 |
| Length, Inch | 27.047 |
| Head Width | 9.80 |
| Head Length | 12.76 |
| Head Area, cm2 | 633.7 |
| Head Area, Sq. Inch | 98.2 |
| Beam Height @ Grip, mm | 22.5 |
| Beam Height @ Mid, mm | 23.8 |
| Beam Height @ Tip | 22.5 |
| Beam Width @ Grip, mm | 18 |
| Beam Width @ Throat, mm | 13.8 |
| Beam Width @ Mid, mm | 11 |
| Beam Width @ Tip, mm | 13.6 (w/Bumper Guard) |
| Number of Main Strings | 16 |
| Number of Cross Strings | 20 |
| Ratio | .614 |
| Main String Grid Inch/mm | 7.56/192.2 |
| Cross String Grid Inch/mm | 10.41/264.4 |
| Density (% of head filled with string) | .768 |
| Average Cross String Space | .520 |
| Average Main String Space | .453 |
| Dynamic Tension, Kp, ERT | 33 |
| Dynamic Tension, Lbs/in | 184.57 |
| First Moment, Nm | .819 |
| Polar Moment | 333.0 |
| Torsional Stability | 16 |
| Swing Weight, Kg/cm2 | 317 |
| Swing Weight, Ounces | 11.18 |
| Swing Weight Calculated | 347.5 |
| Power, RDC | 54 |
| Control, RDC | 44 |
| Manueverability, RDC | 74 |
| Power, Calculated | 2044.1 |
| Head Points | 5.20 |
| Head Weight, % | 47.6% |
| Center of Percussion | 20.9 |
| Dwell Time, ms | 6.83 |
| Efective Stiffness - lbs | 27.3 |
| K, Lb/In | 150.64 |
| Recoil Weight | 151.88 |
| Twist Weight | 233.42 |
| End Weight | 134.4 |
| Tip Weight | 194.4 |
| 9 O'Clock | 97.4 |
| 3 O'Clock | 94.8 |
| Butt End | 137.4 |
| COF, Main | .382 |
| COF, Cross | .315 |
Something with tennis racquets that is important to us is “serviceability”. The Defyer, like most Wilson racquets, has a nice grommet system that protects the string from “court contact” damage, and is “aerodynamic” in shape.
The grip pallet system is another matter, however, and makes grip size and shape modifications difficult, if not impossible. So, when you are making a purchasing decision, be sure you are choosing the correct grip size. This pallet system is not unique to the Defyer, but the Defyer is in the category of “customizable” racquets. Don’t plan on much grip customization!
Head Extreme Pro 2026
If you are thinking of a new 98 square inch high-performance racquet, don’t make a decision until you try this one!
This one is the new Head Extreme Pro for 2026, with a beautiful cosmetic upgrade and material enhancements that improve performance.
Something that you may not notice but is very good is the elongated cross-string holes in the twelve (12) central cross strings’ location. This design increases the effective hitting area by a couple of inches without increasing the head width. This is not unique to the Extreme Series, but it does not show up in the Speed or Gravity series.
| Manufacturer | Head |
|---|---|
| Racquet Model | Head Extreme Pro 2026 |
| Reference Tension | 55 |
| String | MonoGut ZX Pro |
| Machine Used | True Tension Pro |
| String Bed Stiffness - RDC/Units | 50 |
| String Bed Stiffness -FlexFour/Pounds | 63 |
| Strig Bed Stiffness - SBS/Pounds | 43.5 |
| String Bed Stiffness - ERT/Kg/cm | 34 |
| Racquet Flex, RDC/Units | 67 |
| Racquet Flex, FlexFour/Lbs | 43.5 |
| Racquet - In Plane Stiffness/Lbs/Inch | 493.6 |
| Weight, Grams | 330 |
| Weight, Ounces | 11.64 |
| Balance, mm | 323 |
| Balance, Inch | 12.72 |
| Length, Cm | 68.6 |
| Length, Inch | 27.008 |
| Head Width | 9.56 |
| Head Length | 12.87 |
| Head Area, cm2 | 623.8 |
| Head Area, Sq. Inch | 96.7 |
| Beam Height @ Grip, mm | 20.5 |
| Beam Height @ Mid, mm | 23.3 |
| Beam Height @ Tip | 22.4 |
| Beam Width @ Grip, mm | 15.7 |
| Beam Width @ Throat, mm | 134.0 |
| Beam Width @ Mid, mm | 11.5 |
| Beam Width @ Tip, mm | 13.9 w/Bumper Guard |
| Number of Main Strings | 16 |
| Number of Cross Strings | 19 |
| Ratio | .625 |
| Main String Grid Inch/mm | 7.21/183.1 |
| Cross String Grid Inch/mm | 9.63/244.6 |
| Density (% of head filled w/ string) | .728 |
| Average Cross String Space | .507 |
| Average Main String Space | .457 |
| Dynamic Tension, Kp, ERT | 34 |
| Dynamic Tension, Lbs/in | 190.2 |
| First Moment, Nm | .819 |
| Polar Moment | 331.0 |
| Torsional Stability | 14 |
| Swing Weight, Kg/cm2 | 317 |
| Swing Weight, Ounces | 11.18 |
| Swing Weight Calculated | 344.3 |
| Power, RDC | 55 |
| Control, RDC | 48 |
| Manueverability, RDC | 75 |
| Power, Calculated | 2074.2 |
| Head Points | 6.30 |
| Head Weight, % | 47.1% |
| Center of Percussion | 20.9 |
| Dwell Time, ms | 6.62 |
| Efective Stiffness - lbs | 26.4 - Flex Four Data |
| K, Lb/In | 160.26 |
| Dynamic Stiffness/Lbs | 369.5 |
| Dynamic Force/Lbs | 141.8 |
| GDR Ratio: static/dynamic | 1.94 |
| Recoil Weight | 155.24 |
| Twist Weight | 226.4 |
| End Weight | 134.9 |
| Tip Weight | 193.9 |
| 9 O'Clock | 97.5 |
| 3 O'Clock | 95.8 |
| Butt End | 136.9 |
| COF, Main | .348 |
| COF, Cross | .352 |




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