Author Archives: RacquetQuest

An Inside Look at String Evaluation

In this series, we will look at the various characteristics of tennis string without the tennis racquet!

Racquet Quest evaluates every string we use plus strings submitted from other sources. These evaluations are “No Prep” and “Prep”, which simply means the Prep string has been pre-stretched in the entire length. It has not been through a tennis racquet…yet!

The following images represent a string that has not been “prepped.”¬† After these plots are fully understood we will do the same string in the”prepped” format to see if there is a difference.

Ultimate Tensile Strength

What we notice immediately is the string is very “soft” as seen in the deflection of 47.8 mm to reach 50 pounds.¬† Also, the elasticity, the ability to recover to the original length, is fairly low.

The area under the 50-pound and 47.8 mark is the stress/strain curve that shows how the string behaves in three (3) cycles.  The load and number of cycles can be changed.

The long run (linearity) from the 50-pound mark to failure is quite good and suggests consistency.

The UTS, the ultimate tensile strength, of 127.1 pounds is good for this thin string.

The following plot shows the knot strength of this string.

Knot Strength

This plot is overlayed on the previous image so a quick comparison can be made.  It is common for knot strength to be lower than un-knotted string.  Knot strength is primarily important to the person tying the knot.  Knots rarely fail after they are successfully tied.  Pulling a knot too tight or jerking can break a knot.

This plot says to us that this string needs to be handled carefully when it comes to knots!  We would expect a knot strength of at least 80 pounds for typical monofilament strings, however, if this string exhibits extraordinary play characteristics anyone can learn to tie the knots!

You CAN tie knots!

Based on this information we would suggest this string for a player looking for extraordinary comfort, power, and relatively short life!

If, based on what you see here, you want to try it let us know!



So, here IS the difference!

This table will clarify the differences between the Pro Staff Six-One and Pro Staff X models.  While numbers are important, it is equally important to actually hit with the racquet(s) setup as you will be using them.

Pro Staff Six-One versus Pro Staff X

Click here to see the Wilson Pro Staff X

Click here to see the Wilson Pro Staff Six-One data


Pro Stock Limited Reserve

This is a high-performance string that has gone unnoticed for a while and I don’t know why!

Pro Stock Limited Reserve is a string we purchased because it has interesting characteristics that appealed to us however the client base is small.  Recently, however, with the number of players that are moving away from a polyester string, this has become a popular alternative!

The plot below shows why!

Pro Stock Limited Reserve

In a word, this plot looks very much like that of natural gut, and whatever you think natural gut is still considered the best performance material for racquet string!

What are we seeing here:

  • Linearity, the more linear the string the more consistent (predictable)
  • Elongation, at 33.1 mm at 50 pounds
  • Elasticity, 71.9 %
    • This is the area where the advantages of pre-stretching will be seen.
    • The curve will become essentially one line meaning the string returns to a nominal length after stretching.
  • Ultimate Tensile Strength, 163.6 pounds to fail (high), @107.2 mm deflection
  • Knot strength, @102.4 pounds, and surpasses natural gut in this property.

What we can’t see in the plot is the construction of this multifilament string.¬† Each strand is a thin, flat ribbon of polyolefin material.¬† The ribbons are much like the natural gut.

The plot below is a comparison of natural gut string and is included as a visual to compare to Pro Stock Limited Reserve and show how much natural gut fibers are the same for any string manufacturer.  Of course, manufacturing techniques, bonding agents, and coatings make the difference between a good gut and a not-so-good gut!

If you compare the Pro Stock Limited Reserve to natural gut you can quickly see why it may be a good string to try!

And by the way, it is probably at least $25.00 less than natural gut!


So, what IS the difference?

Wilson has presented us with a couple of choices when it comes to choosing a 100-square-inch racquet!

Just what we need…right?

Later we will have a comparison table showing the pertinent property data, but now we can  see the graphics difference between the two racquets:

Pro Staff Six-One 100

ProStaff X v14 100

The Pro Staff Six-One 100 has a very shiny rust color.  The Pro Staff X is the matt finish used on most of the v14 Pro Staff models.

In addition to the “shining,” the Six-One has the “normal” elliptical cross-section, while the “X” has a “box beam” geometry which is a little more narrow.

The Six-One is a Beefier” looking racquet!

The string spacing on the “X” is slightly more open, which may contribute to the power calculation being a bit higher.

The flex of the “X” is a little greater in the shaft area.

That is enough talk!” ¬†

Let’s look at the numbers:

Racquet ModelWilson Pro Staff X 100, v14
Reference Tension55

PEEK 7710
Machine UsedTrue Tension Professional
String Bed Stiffness - RDC50.0 Units
String Bed Stiffness -FlexFour61.0 Pounds
String Bed Stiffness - SBS47.0 pounds
String Bed Stiffness - ERT38 Kg/Cm
Racquet Flex, RDC64 - After Stringing
Racquet Flex, FlexFour47.0
Racquet - In Plane Stiffness467.9 Lbs/Inch
Weight, Grams340
Weight, Ounces11.99
Balance, mm322
Balance, Inch12.68
Length, Cm68.6
Length, Inch27.03
Head Width9.73
Head Length13.06
Head Area, cm2643.4
Head Area, Sq. Inch99.7
Beam Height @ Grip, mm22.3
Beam Height @ Mid, mm22.0
Beam Height @ Tip22.0
Beam Width @ Grip, mm11.00
Beam Width @ Throat, mm11.00
Beam Width @ Mid, mm12.00(PWS)
Beam Width @ Tip, mm12.00(including bumper)
Number of Main Strings16
Number of Cross Strings19
Ratio Cross/Mains.627
Main String Grid7.50
Cross String Grid10.81
Density (% of head filled with string)81.2%
Average Cross String Space.569
Average Main String Space.469
Dynamic Tension, Kp, ERT MasterTensometer38
Dynamic Tension, Lbs/in212.54
First Moment, Nm.841
Polar Moment341.0
Torsional Stability17
Swing Weight, Kg/cm2324
Swing Weight, Ounces11.43
Swing Weight Calculated352.2 (full-length)
Power, RDC53.0
Control, RDC47.0
Manueverability, RDC71.0
Power, Calculated 2088.8
Head Points6.61
Head Weight, %46.9%
Center of Percussion20.8
Dwell Time, ms9.00
Efective Stiffness - lbs28.1
K, Lb/In160.26
Recoil Weight158.85
Twist Weight240.78
End Weight 141.3
Tip Weight 198.9
9 O'Clock102.5
3 O'Clock101.9
Butt Cap135.6
COF, Main.529
COF, Cross.499

Click here to see the Comparison Table


Wrong Planet?

Yesterday a good friend was in the World Headquarters, and as usual, our discussion turned to player training, the necessity, and the over-training of players, mainly juniors!

This training may include the wrong equipment setup, unnecessarily stiff strings, and sometimes stiff, light racquets.  This may cause injuries at every level of player from recreational to professional!

My friend, by the way, is a Collegiate All-American, a professional player, and a coach! 

After we discussed how to change this behavior, she said something quite interesting;

“John, you are on a different planet!”


So two things can happen;

  1.  Abandon my planet
  2.  Invite you to join our planet!

We have chosen number 2!

  • to invite you to our¬†planet!
  • ¬†

¬†There will be no need for interplanetary travel right now, but we do need to pick a name for our planet, so, the person presenting the best name will be the Mayor of our planet (your name here)…for a while.

We hope you will join us and make our planet a place we can all go to discover, learn, share, and understand as much as we can about tennis equipment, customization, stringing, and “best practices”.

Please use the “Leave Comment” tab below to submit your name for our new planet!

Our mission is to keep players playing!