I am seeing a lot of questions pertaining to blade tip speed. Obviously the faster the better, right?....to a point. What I am wondering is, at what speed is the best cut possible at? It would have lots of variables. Blade design is one, blade to baffle distance would be another. Deck design is also important. I'm sure that there are alot of different variables. Also, another variable is engine RPM and what RPM the factory "mower" rates the fpm at. As an example, my '97 Dixie with a 25 Kohler "yeah!" was delivered to me with a free load speed of 3450 RPM. That seemed a little slow, so I looked in the owners manual and found that they should be at 3600 RPM. So I adjusted it to that. Much better cut, like night and day!. Then after reading Lawnsite, and how many ran as high as 3850 RPM, I then adjusted them to 3750 just to be safe. I noticed another improvement in cut. At what speed does Dixie attain the 19000 + fpm speed? 3450, 3600, 3750, or 3850? These jumps in RPM have a measureable affect on blade tip speed as well as quality of cut. Next would be...If the drive pulley on the engine is the same diameter as that on the spindle (are they?) then the spindles turn at the same RPM as your engine. Are some "geared" up or down with pulleys to adjust this spindle RPM? How about the shaft driven decks, are they spinning faster or slower. The length of the blade determines tip speed, so a 72" deck needs to turn slower than a 60" deck. All right, all you engineering students, what is the formula for determining the blade tip speed when spindle RPM is known? How can we learn spindle RPM when it is shaft driven? BOY, do I need to get out there and start cutting or what!!! Sorry for the long post! Carry ON!!!