Cross-string tensions, or actually reference tensions, are the topic of this brief post.
First, every tennis racquet has a “natural” ratio, that is, if the reference tension (and machine setting ) is 50 for both the main string and cross string when the racquet is removed from the stringing machine, the tensions remaining will be in the area of around 50 for the mains and 37 for the cross.
The resultant tension is the natural ratio of that specific racquet.
The issue with changing cross-string tension either higher or lower than the main is that the racquet has changed shape. That is why we test for In-Plane stiffness for every racquet. The higher the In-Plane stiffness, the higher the cross-string tension will remain upon removal from the machine.
If the racquet has very low In-Plane stiffness, it has expanded in width with only the main string installed, so the cross strings need to pull the racquet back into a better (hopefully original) shape.
So, when deciding how much variation you want between the main and cross strings, please consider the racquet! In most cases, we suggest using the same string tension setting for both the main and the cross, since the cross string tension will naturally be lower.
Our True Tension Professional stringing equipment supports the racquet in such a way that we install the main string and cross string at the natural ratio, so the racquet does not change shape and the string bed is consistent.
If you are curious about In-Plane stiffness for a specific tennis racquet, please leave a comment below.