Category Archives: Accuracy

SBS…what is it and why should we care?

We have made several posts regarding SBS, which is “String Bed Stiffness” and this is another one!

If you read this post we really need your comment(s), really!

String bed stiffness is the “feeling” when the ball hits the string on a tennis racquet.  Due to the various string materials there will be “soft” and “hard” feelings.  But wait, there’s more!

The string bed is made up of several strings, some longer called the Main string (M)and some shorter called the Cross string(X).  Using “reference” tension each of the sets of string will be pulled at the same machine setting!  It the machine is set at 50 pounds the tension head will stop pulling when it feels 50 pounds of resistance, regardless of what he tension inside the racquet head may be.

SBS is the most effective data for comparing tennis racquet stringing!

Let’s say you come into the world headquarters and we ask you what SBS you would like to have?  Would you know?  Probably not and not many would!  We have grown up using the term “reference tension”, not SBS.

Reference tension is “number” you would ask your racquet technician to set the stringing machine tension system on.  That number will probably be between 30 and 60 pounds (≈13 to 26 Kilo).

So, depending on many other variables, such as string material, string pattern, stringing machine, stringer technique, etc., you can end up with may different versions of the same “reference tension”.

A better way, and one we have been using for over thirty (30) years, is SBS but not everyone has bought into the concept, even though a qualified racquet technician will have a way to measure SBS!  Maybe because it is too much trouble to figure out what your desired SBS from machine X would be from machine A!  It is not!

There have been several really good SBS data collection devices but they have been difficult to use, and pricy!  Not to mention gigantic!

A call to action!
So here is where you come in,

Would you purchase a SBS data collection device?

How much would you pay for such a device?

Would you prefer a mechanical device or an electronic device?

The device must be portable, that is easily carried in a racquet bag or backpack

    Yes or It doesn’t matter

It must be easy to use.

If you use an SBS device would you use a racquet technician that did not know what SBS is or how to measure it?

Thank you for adding your comments to this discussion!  It is important stuff!


What’s The Difference?

As tennis players, you must constantly ask “what’s the difference” when it comes to tennis racquets and string! Well, as racquet technicians we ask the same questions!

This post is intended to showcase the differences of string in testing, not playing, however, some of the data may be noticeable to the player in certain situations.

What this graph shows us, in addition to our trying to save a tree by printing on the back of previously used paper, is that each of these stings will provide almost the same performance. This is indicated by the curve and how closely related the strings are.

Tensile Strength Comparison

The differences you do see here can be attributed to the gauge, or diameter, of the string, with the largest diameter (Tour Bite) having the highest tensile strength.  Down in the “hitting” displacement range (way below the 39.9mm!), there is very little difference.

The tensile strength can be a factor as the string begins to “notch” or otherwise come apart.  Each of the strings in this graph is monofilament so notching would be the failure mode in a racquet.


Head Prestige Pro 2021

This years Head Prestige Pro is last years Prestige MP.  This name change was made to synchronize all the 18×20 string patterns as the “Pro” model…I think!

So, what’s in a name?  A thin beam, heavy (sort of), 18×20 pattern, players racquet, that’s what!  The Prestige Pro also includes the new Auxetic material and construction for a refined feel.

For some reason Head Prestige racquets have been called “stiff” by some and this is certainly not the case and never has been.   This racquet is not stiff! As with any racquet the string selection can have a huge effect on “stiffness” so take a look at the effective stiffness!

I believe this is going to be a “control freaks” racquet!  This racquet could also be a baseliners dream come true.  The weight will drive through the ball and the swing weight will allow for some last nano-second stroke adjustments.

Take at look at the data below then go to the Prestige 2021 Comparative Data post to see all the models in one place.

A baseliners dream!

Racquet ModelHead Prestige Pro 2021
Reference Tension52 lbs - 23.6 kg
Head Reflex MLT 17
Machine UsedTrue Tension Professional
ASPS, FlexFour62.5
Racquet Flex, RDC58 - After stringing
Racquet Flex, FlexFour36.0
Racquet - In Plane Stiffness326.1 lbs/Inch
Weight, Grams342
Weight, Ounces12.06

Balance, mm318
Balance, Inch12.52
Length, Cm68.6
Length, Inch27.008
Head Width9.48
Head Length13.06
Head Area, cm2627.4
Head Area, Sq. Inch97.2
Number of Main Strings18
Number of Cross Strings20
Ratio Cross/Mains.653
Main String Grid7.56
Cross String Grid10.24
Density (% of head filled with string).791
Average Cross String Space.513
Average Main String Space.417
Dynamic Tension, Kp, ERT35
Dynamic Tension, Lbs/in195.76
First Moment, Nm.832
Polar Moment333
Torsional Stability15
Swing Weight, Kg/cm2318
Swing Weight, Ounces11.22
Swing Weight Calculated345.8
Power, RDC45
Control, RDC56
Manueverability, RDC75
Power, Calculated 1811.5
Head Points7.87
Head Weight, %46.4%
Center of Percussion20.7
Dwell Time, ms8.74
Efective Stiffness - lbs27.7
K, Lb/In169.87
Recoil Weight157.84
Twist Weight230.87
End Weight 143.2
Tip Weight 198.9
9 O'Clock102.8
3 O'Clock100.3
Butt Cap140.3

Head Prestige 2021 Series Comparative Data

Jumping back and forth between reviews and data is not fun nor is it efficient so we have been posting comparative data. Now all the important stuff is in one place.

All of the data is based on a “play ready” racquet.  That means an overgrip and vibration damper, and unless otherwise noted…string!

As you are looking at the data try to determine which numbers mean the most to you and how you could use them.  For example, the Pro has an overall weight of 342 with a swing weight 318.  How does that compare to the MP?

Keep in mind that weight and swing weight can increased but not easily decreased.  No, making the racquet more “head light” statically does not reduce the swing weight as recorded on testing devices that grab the racquet 10cm from the end!  That is why static balance (CG) should not be used as a performance metric.

Click here to see the data!



Head Prestige Tour 2021

This racquet has the potential to be the hottest new Prestige in a long time. The “Tour” series is not new to the Prestige line but this one has some differences that are meaningful, we think!

This new Tour is a 16×19 string pattern inserted into a 95 square inch hitting area! Compare that to the previous Tour with a 18×19 string pattern in a 99 square inch head(now the new Prestige MP)…so you can see where this one is headed!

All of the new Prestige 2021 racquets will come with the full cap system that has become the “iconic” Prestige accoutrement.  

Also included in the Prestige Tour is the Auxetic material and construction that is intended to provide a better feeling impact and maybe a little more “energy”.  The shaft has a slightly different geometry and is a little shorter than some other models, however, the graphics indicate the shaft is “elongated”.

The “box” beam is a relatively constant 22mm from start to finish and is beautifully done in matt black transitioning into the Prestige maroon.

Racquet ModelHead Prestige Tour 2021
Reference Tension53 lbs - 24.0 kg
Victrex 7718 (PEEK)
Machine UsedTrue Tension Professional
ASPS, FlexFour63.5
Racquet Flex, RDC63 - After stringing
Racquet Flex, FlexFour42.5
Racquet - In Plane Stiffness384.6 lbs/Inch
Weight, Grams336
Weight, Ounces11.85

Balance, mm326
Balance, Inch12.83
Length, Cm68.5
Length, Inch26.968
Head Width9.406
Head Length12.78
Head Area, cm2608.9
Head Area, Sq. Inch94.4
Number of Main Strings16
Number of Cross Strings19
Ratio Cross/Mains.620
Main String Grid7.20
Cross String Grid9.125
Density (% of head filled with string).695
Average Cross String Space.464
Average Main String Space.445
Dynamic Tension, Kp, ERT34
Dynamic Tension, Lbs/in190.16
First Moment, Nm.844
Polar Moment347
Torsional Stability16
Swing Weight, Kg/cm2331
Swing Weight, Ounces11.68
Swing Weight Calculated357.1
Power, RDC53
Control, RDC47
Manueverability, RDC66
Power, Calculated 1968.0
Head Points5.20
Head Weight, %47.6%
Center of Percussion21.1
Dwell Time, ms9.00
Efective Stiffness - lbs27.9
K, Lb/In160.26
Recoil Weight161.61
Twist Weight223.59
End Weight 136.8
Tip Weight 200.6
9 O'Clock99.5
3 O'Clock101.4
Butt Cap134.9