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Old 02-05-2013, 01:22 PM   #195
Join Date: Jul 2008
Posts: 5,440

Originally Posted by mikeler View Post
I don't think you can buy the RSI stiffness numbers on this one. The Dynamite is fairly stiff or firm even at 50 pounds in my Exo Tours.
I always buy the stiffness numbers because it is a very straightforward property of the strings that is easily measured. Whether or not it feels as "soft" as the stiffness number would suggest is another story, but the measured stiffness is a known fact, regardless of how it feels. But I know what you mean. I'm just opposed to the knee-jerk reaction that I hear sometimes on the board that if a string doesn't feel like the stiffness measurement suggests, then the stiffness measurement is bogus. I think this is very unwise. It's like admitting that we don't understand something and then, instead of searching for more facts to improve our understanding, we throw away one of the few facts that we posess. Doesn't make sense to me.

My hypothesis for your experience with Dynamite remains the one I suggested earlier - that Dynamite, having the highest string on string friction of any strings tested, resists string movement and acts more or less as though the strings are locked in place. As I mentioned before, strings that are free to slide increase dwell time and thereby reduce impact shock. But there is something else that could be at play here that is related. The lab stiffness numbers are taken from lengths of string that are tensioned and then struck with a hammer with controlled force. The elongation of the string during that impact is measured and that's where the stiffness numbers come from. But in a racquet, the effective length of each string can be much shorter than the piece tested in the lab. If the strings were glued or bonded at the intersections, then each length would be as short as the distance between each intersection, so like 1 cm. Conversely, if the strings are slippery and free to slide around, the stretched length could be much longer, even as long as the entire grommet-to-grommet distance. It could be that short lengths of Zyex are disproportionately stiffer than long lengths, so that if the strings are relatively immobile they will actually be stiffer than if they were free to slide around. If this were the case, then you would be right - we should not buy the stiffness numbers we have because they are derived from a longer length of string than what is actually being stretched in a strung racquet. Just a guess, really, and I hope I'm making sense.

If this were the case, though, it could also help explain the stiff feeling Torres experienced on the edges of the stringbed with the slippery ZX.
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