Pre-stretching poly strings


"Prestretching will destroy the elasticity and the string will not perform as designed"

- yes, by prestretching you will "change" the string, you will remove the "lasting" elongation. (= the elongation that "stays" when you go back to zero pull-tension)
- no, you will NOT remove the elasticity of the string
- yes, the strting will feel different. You can compensate by reducing the ref.tension.


You can determine if a polyester like string has been prestretched. Its total tension loss percentage drops to a mere 30% or less. This can be contrasts with those that have not been prestretched where total tension loss is betwwen 40 and 50%. Without the prestretch, every ball impact creates some micro stretching which is not recovered. This is because the string can still relax further structurally. [Actually the term relax is not correct. The proper description is that the alignment of the polymers increase.] When it gets to the point that it can no longer flow plastically is when it becomes elastic. It can also stretch enough that ball impacts no longer have enough energy to stretch the strings further.


I prestretch my poly crosses (NG mains) and it's huge help in maintaining the life of the hybrid stringbed.
It's only there to allow the NG to do it's thing, so a perfect method for me.

Jerry Seinfeld

Tell that to Kirschbaum who prestretches their poly strings at the factory
Gladly. Kirshbaum strings are manufactured by a manufacturer based in Germany not by Kirshbaum themselves. This manufacturer actually understands poly based strings and it is highly unlikely they are "prestretched" using any traditional definition. There of course can be some stretching in the coiling process, which may be marketed as a prestretch by Kirshbaum. I stand by my statement that poly based strings should NOT be prestretched.

Injured Again

Hall of Fame
I've played almost exclusively with poly strings for probably the last 15 years if not more, and have been stringing for myself and clients for most of that time. I've used poly strings without any pre-treating, with a light prestretch to remove coil memory, with a hard prestretch to get better tension majntenance.

Installing poly strings with no prestretch makes for the liveliest initial stringbed. If I were a pro who plays with a racquet for no more than an hour and restrings, this is absolutely what I would do. Unfortunately, I'm a recreational player who typically plays poly strings until breakage, which is eight to ten hours. So while the first hour of performance is important, equally important are hours two through ten. Without a prestretch, the playing characteristics change more over the life of the string and that, by far, is a greater consideration than a bit more liveliness that first hour or two.

If someone needs back the liveliness from a poly string, then I always steer them towards a different string rather than the same string with no prestretch.