Tennis strings are elastic and they stretch out and lose their resiliency. This resiliency is the ability of the string to snap back into position during the hitting a tennis ball. The old strings have been held at a tension of 50-60 pounds for an extended time and they cannot function like when they were new. Just because strings are not broken doesn't mean they are still good. They are still there but the strings are not working to the top of their ability.
Strings that have a lot of use will stretch and lose tension also. You can have your strings tested to see if there has been any significant tension loss. Tension loss is relative since we need to have the strings tension tested right after stringing to be able to compare to the current tenison.
We have two kinds of tension terms. Reference tension is what your stringer sets his or her machince at to string your racquet. The second and most important is the actual tension. This is the tension reading of the actual string bed stiffness. This reading is done by several different devices but if it is best when your actual tension is measured right after the string job and again after some length of time. The difference between these two readings will give you a very accurate tension loss.
Does your racquet stringer measure your strings tension after stringing? If not then you have really very little idea of what your actual string tension is. Their reference tension to actual tension could vary as much as 10-15 pounds.
Does your racquet stringer clean his machines clamps regularly? If a stringer or machince has dirty or loose clamps the string can slide through during the stringing process and produce a inaccurate tension compared to the reference tension. Stringers call this slip, slop! Go figure, because that's exactly what it is, sloppy tensioning.
Does your racquet stringer calibrate his or hers machine regularly? If your stringer doesn't , then the tension you ask for might be nowhere near the tension the machine's tensioning device is pulling.
Is your racquet being strung by different people? The same person, using the same machine will usually produce different results. Could you imagine a different person using the same machine? Different people stringing the same racquet on the same machine can produce results that vary as much as 10-15 pounds in tension.
The bottom line is that you should have your tennis racquet strung on a regular basis, even if the strings are not broken. Find a reliable, professional stringer and stick with them to have consistent string tensions. And, now you know the rest of the story!
Doug Hofer, USPTA & USRSA January 23, 2004
