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.