man this again, you guys need to do more searches before you flame. basic story, a stringer gotten hold of Federer's racquet and did an in depth comparison between the racquet, N90 and PS85. the conclusion is that it's a customized N90.
No, you need to be more thorough in your research. Greg (the guy you refer to as "a stringer"...but who is actually the USRSA webmaster and magazine editor...who did the article you're referring to, in case you didn't know) did the review well before the K90 was released, and before layup information came to light about it and previous versions of Fed's frame and retail ones. He also did the review based on an N90 that came from Wilson's pro room and not off the shelf, and he did it before there was a retail K90 to compare it to. So at that point, the N90 he got was the closest frame to what Fed was using, but there were still quite a few palpable differences. In fact, here's his quote:
"Although I had noticed the spacing differences between the retail and Federer versions of the nSix-One Tour 90, they really hit home during stringing. The grommet holes for the Federer version do not conflict as much with the side supports on the SP Pro Cord, and there is plenty of space for the tie-off knot for the crosses. I can't explain the lower swing weight of our retail nSix-One Tour 90, as illustrated in this table."
However, with the release of the K90, these differences were no longer visible or measurable, suggesting that it, in fact, was the frame Fed had used all along (since 2003).
As VSBabolat stated above, it has been pretty well established, since the writing of the article you refer to, that the layup Fed uses is closest in all of its properties to what would eventually become the K90 version. The P1 boys have also made various posts on these boards that suggest the same. And as even Greg noted in the article in question, the drill pattern of the N90 was visibly different from the one that Roger used at the time. Meanwhile, the K90's retail drill pattern is a match for the one that Roger has used all along (and continues to). While it's possible to change drill patterns via the pro room, the retail racquet closest to what Fed has used all along is, for many reasons, the K90, and there is no evidence now to suggest that he has ever used anything else since 2003.
If you'd like, you can contact Greg yourself, as he, too, now believes that the K90 is the racquet Fed has used all along. He believed that the N90 was a slightly dumbed down version that would be easier for the average player to use, as is the BLX. So if even the author of the article you're referring to disagrees with you, it leaves just you who believes what you do. The fact that you haven't put together all the available info in a complete fashion suggests that maybe you have some reason for wanting to believe that Fed changes racquets every two years, even though no other pro on the tour does this. That doesn't change the fact that you're wrong, though.
N.B. At the risk of getting too technical, I'll try to simplify some of the tech aspects for you. When the article refers to "n-coding", they're talking about the use of silicon dioxide bits that are added to the materials from which the frames are made, in an effort to eliminate the spaces in the material, and thus make it stiffer in spots. The silicon dioxide is not part of the initial graphite/carbon raw materials, but introduced to them to change their properties. While Wilson uses a proprietary jargon term for their racquets, the process is exactly the same as what every other company does when they say they're using "nano" technology or similar. Basically, they're filling up the cracks and airspaces in the graphite with stuff. So Greg's assessment article only tells us that he thinks Wilson's post-2002 frames feel different from the earlier ones, because they have this process done to them, which obviously is true. However, the K-Factor series also used the same process and a version of the same silicon dioxide material. It's a pretty common process these days with many manufacturers, and there would have been no way to differentiate one version of it from another just by feeling the frame during play, especially since the K version hadn't been released yet. So there would have been no way to know that K (which hadn't been released yet) would feel the same or different from N, just that the new frames felt different from the old.
Therefore, all you can learn from that article is that Roger did indeed switch racquets in 2003, which is something we all already agree on. It's easy to buy into the marketing speak and assume that the N's all had one technology while the K's had a completely other one, but really they were both based on the same type of tech. In the end, the outdated article does nothing to help establish that Fed ever used a racquet based on the retail N90, unless you don't have the technical background to understand the info.
