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.