Category Archives: Accuracy
Tolerance – Why and How Much?
This topic comes up frequently when clients are at Racquet Quest’s World Headquarters. But what if you are not at the World Headquarters?
Play Better Longer
For many years, we have been testing all racquets for string bed stiffness, effective stiffness, flexural stiffness, in-plane stiffness, and about any other stiffness you can imagine.
Throughout this process, we were also testing the strings for power potential, creep, string-on-string friction, and linearity.
Linearity is a significant property of string; however, it does not get the attention we believe it deserves. So, this little post will begin to change that. We will start with some images and explain what we see in them.
String Behavior
Four different string materials are represented here from left to right:
- RPM Blast
- IsoSpeed Polypropylene Composite
- Babolat VS Touch Natrual Gut
- Ashaway MonoGut ZX Polyether ether ketone (PEEK)
The entire chart is important, but the real property we are interested in for this post is “linearity”.
- Linearity is how straight the plot is from the beginning to failure.
- Failure is the vertical line associated with each string material.
A glance will show MonoGut ZX with the longest linear track, however, Babolat VS Touch is the very “straightest”, followed by IsoSpeed and RPM Blast.
OK, but why do we care? We care because when we say a string will play better longer, it is based on the linearity which is the property directly related to consistency.
Better predictability = better performance
Players perceive predictability more than raw stiffness.
A string that ages predictably plays better longer, even if it’s not the softest or most powerful.
That’s it!
Now all we need to do is quantify “better”.
I will leave that up to you.
Take a Guess?
A very good player and client came into the World Headquarters Wednesday with his three (3) Tecnifibre TF40 315’s wanting to re-string. There is nothing unusual about that except this time he wanted to discuss different strings. So we did!
The final three (3) strings under discussion were:
- Tecnifibre Razor Soft 17 (current string)
- Volkl V-Star 17
- MonoGut ZX Pro 17
The first two are considered to be polyester, however, I am not sure V-Star fits entirely in that category, and PEEK is the material with the MonoGut ZX Pro name. All of the strings are monofilament.
We learned in a previous post “a picture is worth a thousand words”, so we are including a picture to help in our guessing.
Take a Guess?
Here are some basic properties of the subject racquet that may contribute to your guess
- Weight=342
- Swing Weight=327
- RDC Flex=63
- Flex Four Flex=50.8
- Grip Size= 3
We hope you will make a guess in the “comment field” below and if you do you can use the string name or the color…we will figure it out, and thank you for you guess!
Accuracy Index…What is it?
For several years, Racquet Quest has been testing racquets we have strung for an “Accuracy Index.” Click here to see an example, and then we will discuss it.
For several years, Racquet Quest has been quantifying racquet string bed behavior using our internally developed Accuracy Index. This post was drafted in 2019 but not posted util now. Why now? Players, and us, are even more frustrated with the lack of quality racquet preparations than we were in 2019! We are seeing more and more really bad stuff happening so this post may be a way to address the bad stuff and do better!
The first graph presents the relative stiffness of the main and cross string arrays, as well as the average composite stiffness. On the following page, the Accuracy Index data grid provides a segmented view of the string bed, with each color-coded cell corresponding to a specific impact zone.
This grid allows us to analyze local stiffness variations, where, for example, light blue cells typically correlate with premature failure points in topspin-oriented play. The example shown references a standard 16×19 string pattern, but the analytical framework is applicable to any string configuration.
Why does the Accuracy Index matter?
In performance terms, control is effectively a function of predictability. That is, the extent to which the string bed returns the ball along an expected trajectory with minimal variability. The Accuracy Index quantifies this by comparing actual deflection characteristics across the bed to idealized stringbed behavior. Higher accuracy values imply lower angular deviation and more consistent ball exit vectors.
We also report an Efficiency Index, which assesses how effectively the stringing process preserved the frame’s intended geometric and mechanical properties. A lower efficiency score (e.g., 71) indicates that the racquet had to internally redistribute loads—compensating for distortions incurred during stringing. This can result in non-uniform string tensions and unintended stiffness profiles across the bed, reducing both playability and predictability.
At Racquet Quest, our stringing systems utilize frame stabilization techniques that eliminate distortion during tensioning. As a result, our stringbeds exhibit minimal deviation from target parameters, allowing both Accuracy and Efficiency indices to remain at consistently elevated levels.
Implications for Racquet Technicians
Regardless of the equipment used, technicians can leverage the Accuracy Index as a diagnostic tool to identify inconsistencies introduced during stringing. Adjustments to clamping sequences, pull timing, frame support, or pre-stretch protocols can measurably improve stringbed linearity and reduce compensatory distortion.
In essence, a higher Accuracy Index isn’t just a number—it’s an indicator of a racquet’s ability to perform as engineered, shot after shot.
Racquet Quest, LLC
