Category Archives: News!

Numbers, numbers, numbers! What do they mean?

With each of our racquet reviews a long list of numbers is included.  It has been a few years since we explained what these numbers mean so here it is;

Numbers are your friend!
Racquet ModelHead Radical MP 2023
Reference Tension55 (what you tell the stingers to set the stringing machine).
This should be replaced by String Bed Stiffness (SBS)
MonoGut ZX Pro
Machine UsedTrue Tension Professional
String Bed Stiffness - RDC53.0 Units (Babolat RDC)
String Bed Stiffness -FlexFour64.9 pounds (Flex Four)
String Bed Stiffness - SBS51.8 pounds (Racquet Quest string bed stiffness SBS Master)
String Bed Stiffness - ERT35 Kg/Cm (previously Beer's ERT1000)
Racquet Flex, Babolat RDC65 - After stringing (unstrung racquets will be slightly stiffer. Loaded from the tip)
Racquet Flex, FlexFour44.5 (Loaded from the COP)
Racquet - In Plane Stiffness379.7 lbs/Inch (stiffness across the 3 ad 9 o'clock positions of the racquet head)
Weight, Grams326
Weight, Ounces11.50
Balance, mm333
Balance, Inch13.11
Length, Cm68.57
Length, Inch27.00
Head Width9.63
Head Length12.79
Head Area, cm2623.0
Head Area, Sq. Inch96.7
Beam Height @ Grip, mm21.0 (how thick the racquet is looking at the side)
Beam Height @ Mid, mm22.5 (how thick the racquet is looking at the side)
Beam Height @ Tip20.5 (how thick the racquet is looking at the side)
Beam Width @ Grip, mm12.5 (how thick the racquet is looking at the front or face view)
Beam Width @ Throat, mm11.5 (how thick the racquet is looking at the front or face view)
Beam Width @ Mid, mm12.8 (how thick the racquet is looking at the front or face view)
Beam Width @ Tip, mm12.8 (how thick the racquet is looking at the front or face view)
Number of Main Strings16
Number of Cross Strings19
Ratio Cross/Mains.634 ( typically the natural ratio)
Main String Grid7.18 (the distance between the two outer most main strings)
Cross String Grid9.44 (the distance between the two outer most cross strings)
Density (% of head filled with string)69.6% (how much of the head area is filled with string)
Average Cross String Space.494 (how far apart the strings are). The farther apart the quicker the wear.
Average Main String Space.449
(how far apart the strings are). The farther apart the quicker the wear.
Dynamic Tension, Kp, ERT35 (string bed stiffness in kilos per centimeter)
Dynamic Tension, Lbs/in195.76 (DT converted to pounds per inch)
First Moment, Nm.841 (sometimes called pickup weight)
Polar Moment347 (torsional weight)
Torsional Stability16 ( resistance to twisting on off center hits)
Swing Weight, Kg/cm2331 (the dynamic weight and the most significant property)
Swing Weight, Ounces11.68
Swing Weight Calculated361.5 (calculated from the butt end to the tip)
Power, RDC52 (property calculated by Babolat RDC)
Control, RDC49 (property calculated by Babolat RDC)
Manueverability, RDC66 (property calculated by Babolat RDC)
Power, Calculated 2101.4 (calculation based on several racquet properties)
Head Points3.15 ( a point is generally consider to be .125 inches/3.18mm)
Head Weight, %48.5%
Center of Percussion21.1 (highest COR)
Dwell Time, ms8.74 (length of time the ball is in contact with the string without a swing)
Efective Stiffness - lbs29.2 ( the calculated combined stiffness of the racquet and sting bed)
K, Lb/In169.87 (string bed stiffness in pounds/inch)
Recoil Weight156.44 (resistance to twisting about the grip)
Twist Weight226.48 (resistance to twisting about the neutral axis)
End Weight 126.0 (two scale system to calculate CG)
Tip Weight 197.7 (two scale system to calculate CG)
9 O'Clock105.1 (three scale system to assure symmetry)
3 O'Clock104.7(three scale system to assure symmetry)
Butt Cap115.6 (three scale system to assure symmetry)
COF, Main.416 (the stickiness of the string bed sliding the ball with the main strings)
COF, Cross.388(the stickiness of the string bed sliding the ball with the cross strings)

Clamp Riser…your friend!

We are re-introducing our Clamp Riser!

Clamp Riser Set


The Clamp Riser eliminates the need to pull two main strings to start a string job!  There is really no need to use that procedure.

Without going into a lengthy reason for that, suffice it to say the Clamp Riser will be your friend!

Any stringing machine with long, rotating string clamps is too low to capture the string properly for the first tension pull.  The Clamp Riser fits under the clamp and…raises it!

The clamp will now hold the string securely at the proper height for the first pull, one string at a time!

Clamp Riser Babolat



The Babolat Racket Station can use the 20mm height riser side, as seen here, and many other machines can probably use that height as well.

Clamp Riser Baiardo

We have found that Baiardo prefers the 30mm height, as seen here.  The riser height must be enough to allow the clamp base to “lock”.


The Clamp Riser is sold as a set of two (2) to justify the shipping cost!  $17.99 per set.

 Purchase now

Charges for shipping outside the US will be added to the total cost minus the US shipping charge.




Comparing Racquets (for real)

The Racquet Quest podcast recently aired a session on comparing racquets, so, to be fair I wanted to post that same data here. If you listened to the podcast this will sound familiar.

These racquets are not random. These racquets are owned by a client that is seeking an upgrade without going overboard!

Here is the data.  Take a look then read what the client has to say about them.

3 racquetcompare

Here is what Jess has to say:

“Hey, John –
Jess definitely likes the VS more than the Rafa. She said that she gets more easy power and stability with the Rafa but she’s able to accelerate faster on the forehand side with the VS.

She also felt like the VS was more maneuverable at the net. She said that if she’s in control of the point that she can really whip her forehand for a winner. She definitely noticed the lighter swing weight and liked that.

However, she also said that sometimes it feels a little unstable – like the VS is getting pushed around a bit. For example, she noticed that the head of the racquet can twist sometimes if her opponent nails a hard ball at her.

She has more control for sure with the VS – felt like she blasted more balls out with the Rafa. Overall, she likes the racquet- just would like a little more stability.”

By the way, Jess had not seen the racquet data prior to her hitting.  So, there you have it.  I believe you can see how much numbers help us find the right performance characteristics for a racquet.


String Savers

String savers are on my mind today for several reasons so I thought I would post something about them that may be of interest.  Let’s see!

String Savers are tiny little pieces of material that are “grooved” to cradle the string and provide a tiny barrier between rubbing strings, therefore creating a longer, happier life!

String Savers are normally used when stringing your tennis racquet with natural gut string to help the $75.00 job last longer.

But what else do string savers do?

Well, in the case we see here it increases the swing weight from 332 to 341! So 286 of these tiny things have an impact on swing weight! 

Probably the typical reaction would be an increase in string bed stiffness but that is not the case, plus the string bed stiffness is ever-changing anyway.

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!