NOTE 2: There seems to be some arguments going on about measuring clubs with or without grips. I gather it's heated at times. The equations I described in Tech Note 1 are for what we call undamped systems. In theory once they start oscillating they never stop. There is nothing in the system to damp out the vibrations. In nature no such systems exist. You have frictional forces such as air producing drag, the molecules rubbing together and any number of things that will eventually damp out the vibrations. In my past life we built a unique vibratory gyroscope which when rung like a bell would continue to ring or oscillate for hours! Needless to say its damping was inversely proportional to its cost. In a golf club we have damping due to air resistance, the flex of the shaft and subsequent stretching and compressing of the surfaces with paint on them and the frictional losses in the clamp. These are all rather small compared to the damping of a rubber grip. Damping always does one thing to a vibratory system; it always reduces its frequency. Needless to say the damping can be such that no oscillation occurs at all. This is obviously what a good set of shocks does on your car. The effects of air, paint, etc. are fairly small, unfortunately the grip may have as much as a 10-cpm effect. This is one full flex. If a clamping system is built which really crushes the grip the effect can be lowered but now the stiffness measurement is strongly affected by clamping pressure. I much prefer to do my testing without grips. I think grips just cloud the issue. I don't believe the stiffness measured with a grip is what we want to use to fit a set of clubs. If the damping of the grip is a factor in fitting then we should concern ourselves with the toughness of the golfer's hands. Is he a blacksmith or an accountant? A man or a woman? Tight grip or loose?