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.

Yonex Muse 100

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!

ManufacturerYonex
Racquet ModelMuse 100
Reference Tension54
String
MonoGut ZX Pro
Machine UsedTrue Tension Pro
Static
String Bed Stiffness - RDC/Units52
String Bed Stiffness -FlexFour/Pounds60.0
String Bed Stiffness - SBS/Pounds29.9
String Bed Stiffness - ERT/Kg/cm35
Racquet Flex, RDC/Units54
Racquet Flex, FlexFour/Lbs29.9
Racquet - In Plane Stiffness/Lbs/Inch409.6
Weight, Grams321
Weight, Ounces11.32
Balance, mm325
Balance, Inch12.80
Length, Cm68.6
Length, Inch27.008
Head Width9.68
Head Length12.63
Head Area, cm2619.2
Head Area, Sq. Inch96
Beam Height @ Grip, mm23
Beam Height @ Mid, mm25.0
Beam Height @ Tip25.2
Beam Width @ Grip, mm16.7
Beam Width @ Throat, mm14.7
Beam Width @ Mid, mm12.4
Beam Width @ Tip, mm14.2 w/Bumper Guard
Number of Main Strings16
Number of Cross Strings18
Ratio.681
Main String Grid Inch/mm7.25/184.5
Cross String Grid Inch/mm9.13/231.9
Density (% of head filled w/ string).699
Average Cross String Space.514
Average Main String Space.453
Dynamic
Dynamic Tension, Kp, ERT35
Dynamic Tension, Lbs/in195.7
First Moment, Nm.804
Polar Moment324
Torsional Stability14
Swing Weight, Kg/cm2310
Swing Weight, Ounces10.93
Swing Weight Calculated339.1
Power, RDC40
Control, RDC62
Manueverability, RDC80
Power, Calculated 1622.8
Head Points5.67
Head Weight, %47.0%
Center of Percussion20.8
Dwell Time, ms6.49
Efective Stiffness - lbs19.96 (Flex Four Data)
K, Lb/In166.7
Dynamic Stiffness/Lbs294.6
Dynamic Force/Lbs126.7
GDR Ratio: static/dynamic1.53
Recoil Weight149.8
Twist Weight225.1
End Weight 128.5
Tip Weight 192.2
9 O'Clock99.1
3 O'Clock97.0
Butt End1249
COF, Main.356
COF, Cross.277

Tecnifibre Fire 300

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.

ManufacturerTecnifibre
Racquet ModelFire 300
Reference Tension54
String
MonoGut ZX Pro
Machine UsedTrue Tension Pro
Static
String Bed Stiffness - RDC/Units45.9
String Bed Stiffness -FlexFour/Pounds61.1
String Bed Stiffness - SBS/Pounds46
String Bed Stiffness - ERT/Kg/cm33
Racquet Flex, RDC/Units73
Racquet Flex, FlexFour/Lbs46
Racquet - In Plane Stiffness/Lbs/Inch537.2
Weight, Grams324
Weight, Ounces11.3
Balance, mm323
Balance, Inch12.72
Length, Cm68.7
Length, Inch27.047
Head Width9.98
Head Length12.72
Head Area, cm2643.2
Head Area, Sq. Inch99.7
Beam Height @ Grip, mm25
Beam Height @ Mid, mm25.3
Beam Height @ Tip24.8
Beam Width @ Grip, mm15.5
Beam Width @ Throat, mm13.8
Beam Width @ Mid, mm11.2
Beam Width @ Tip, mm12.2 w/Bumper Guard
Number of Main Strings16
Number of Cross Strings19
Ratio.661
Main String Grid Inch/mm8.18/207.7
Cross String Grid Inch/mm9.87/250.7
Density (% of head filled w/ string).794
Average Cross String Space.513
Average Main String Space.508
Dynamic
Dynamic Tension, Kp, ERT33
Dynamic Tension, Lbs/in185.6
First Moment, Nm.804
Polar Moment335
Torsional Stability15
Swing Weight, Kg/cm2320
Swing Weight, Ounces11.29
Swing Weight Calculated338
Power, RDC65
Control, RDC32
Manueverability, RDC73
Power, Calculated 2352.1
Head Points6.46
Head Weight, %47.0%
Center of Percussion21.4
Dwell Time, ms7.22
Efective Stiffness - lbs26.2 - Flex Four Data
K, Lb/In134.6
Dynamic Stiffness/Lbs369.5
Dynamic Force/Lbs141.8
GDR Ratio: static/dynamic1.94
Recoil Weight161.2
Twist Weight240.6
End Weight 130.9
Tip Weight 190.3
9 O'Clock97.1
3 O'Clock96.2
Butt End129.9
COF, Main.350
COF, Cross.262

Wilson Defyer Pro 98 v1.0

Wilson Defyer Pro 98 v1

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.

ManufacturerWilson
Racquet ModelDefyer Pro 98 v1
Reference Tension56
String
MonoGut ZX Pro
Machine UsedTrue Tension Pro
Static
String Bed Stiffness - RDC47
String Bed Stiffness -FlexFour61
Strig Bed Stiffness - SBS51.7
String Bed Stiffness - ERT33
Racquet Flex, RDC65
Racquet Flex, FlexFour51.5
Racquet - In Plane Stiffness474.4
Weight, Grams325
Weight, Ounces11.46
Balance, mm327
Balance, Inch12.87
Length, Cm68.7
Length, Inch27.047
Head Width9.80
Head Length12.76
Head Area, cm2633.7
Head Area, Sq. Inch98.2
Beam Height @ Grip, mm22.5
Beam Height @ Mid, mm23.8
Beam Height @ Tip22.5
Beam Width @ Grip, mm18
Beam Width @ Throat, mm13.8
Beam Width @ Mid, mm11
Beam Width @ Tip, mm13.6 (w/Bumper Guard)
Number of Main Strings16
Number of Cross Strings20
Ratio.614
Main String Grid Inch/mm7.56/192.2
Cross String Grid Inch/mm10.41/264.4
Density (% of head filled with string).768
Average Cross String Space.520
Average Main String Space.453
Dynamic
Dynamic Tension, Kp, ERT33
Dynamic Tension, Lbs/in184.57
First Moment, Nm.819
Polar Moment333.0
Torsional Stability16
Swing Weight, Kg/cm2317
Swing Weight, Ounces11.18
Swing Weight Calculated347.5
Power, RDC54
Control, RDC44
Manueverability, RDC74
Power, Calculated 2044.1
Head Points5.20
Head Weight, %47.6%
Center of Percussion20.9
Dwell Time, ms6.83
Efective Stiffness - lbs27.3
K, Lb/In150.64
Recoil Weight151.88
Twist Weight233.42
End Weight 134.4
Tip Weight 194.4
9 O'Clock97.4
3 O'Clock94.8
Butt End137.4
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.

Head Extreme Pro 2026

ManufacturerHead
Racquet ModelHead Extreme Pro 2026
Reference Tension55
String
MonoGut ZX Pro
Machine UsedTrue Tension Pro
Static
String Bed Stiffness - RDC/Units50
String Bed Stiffness -FlexFour/Pounds63
Strig Bed Stiffness - SBS/Pounds43.5
String Bed Stiffness - ERT/Kg/cm34
Racquet Flex, RDC/Units67
Racquet Flex, FlexFour/Lbs43.5
Racquet - In Plane Stiffness/Lbs/Inch493.6
Weight, Grams330
Weight, Ounces11.64
Balance, mm323
Balance, Inch12.72
Length, Cm68.6
Length, Inch27.008
Head Width9.56
Head Length12.87
Head Area, cm2623.8
Head Area, Sq. Inch96.7
Beam Height @ Grip, mm20.5
Beam Height @ Mid, mm23.3
Beam Height @ Tip22.4
Beam Width @ Grip, mm15.7
Beam Width @ Throat, mm134.0
Beam Width @ Mid, mm11.5
Beam Width @ Tip, mm13.9 w/Bumper Guard
Number of Main Strings16
Number of Cross Strings19
Ratio.625
Main String Grid Inch/mm7.21/183.1
Cross String Grid Inch/mm9.63/244.6
Density (% of head filled w/ string).728
Average Cross String Space.507
Average Main String Space.457
Dynamic
Dynamic Tension, Kp, ERT34
Dynamic Tension, Lbs/in190.2
First Moment, Nm.819
Polar Moment331.0
Torsional Stability14
Swing Weight, Kg/cm2317
Swing Weight, Ounces11.18
Swing Weight Calculated344.3
Power, RDC55
Control, RDC48
Manueverability, RDC75
Power, Calculated 2074.2
Head Points6.30
Head Weight, %47.1%
Center of Percussion20.9
Dwell Time, ms6.62
Efective Stiffness - lbs26.4 - Flex Four Data
K, Lb/In160.26
Dynamic Stiffness/Lbs369.5
Dynamic Force/Lbs141.8
GDR Ratio: static/dynamic1.94
Recoil Weight155.24
Twist Weight226.4
End Weight 134.9
Tip Weight 193.9
9 O'Clock97.5
3 O'Clock95.8
Butt End136.9
COF, Main.348
COF, Cross.352