Originally Posted by Ramjet
Isnt the theory that doing this will allow the gut to slide across the poly cross and snap back. If you put poly in the main wouldnt it actually negate the spin becuase it wouldnt slide as easily across the gut crosses?
Gut mains, and Poly crosses have the among the lowest COF (coefficient of friction) of all the string beds that have been measured for such. This can be confirmed with a visit to the friction tool provided here : http://twu.tennis-warehouse.com/lear...OFreporter.php
This specific hybrid combination is even more slippery than full beds of the slickest co-polys. That's still a bit of a mystery, we don't know for sure why that happens. What we do know for sure is that for whatever reason, hybrids (even of the same material), are more slippery than full sets. A clever squirrel would then guess that the recipe for a the slickest string bed would be to select the two smoothest co-polys from different brands and lace 'em up together. Doesn't work that way. Gut M's, and Poly X's are still more slippery by comparison. The most plausible theory is that there are natural oils present in the gut which are released onto the poly crosses as they swing over them, and that these oils act as a lubricating agent.
However, when you reverse the situation, and go with Poly mains, and gut crosses, that set up has amongst highest measured COF.
Of the two types of friction, (ball to string friction, and string to string friction), it has been observed, confirmed, and re-confirmed again, that low string to string friction plays a much more important role to spin production than hi string to ball friction.