well that thread is definitely hijacked
any body feel up to the task to explain to a really stupid person(that would be me) how to measure MgR/I on a racket? a how-to rather than a why
Yeah, this should probably be moved, but...
Basically, if you have two racquets with the same mass and swingweight, but with difference balance points, the one with balance point furthest from the butt will have higher MgR/I. The frequency of oscillation will be higher and it will feel like it comes through the contact zone faster, in relation to the speed of the arm and hand. At least it feels that way to some people.
If you have two racquets with the same mass and balance point, the one with the lesser swingweight will have higher MgR/I and will feel faster through the contact zone.
If you have two racquets with the same swingweight and balance point, the one with the greater mass will have the higher MgR/I and will feel faster through the contact zone.
The equation is Mass (kg) * balance point (R, in cm) * g (981) divided by I (swingweight 10 cm beyond the buttcap (the approximate wrist joint axis))
The equation for I is (Swingweight + (20*mass(kg)*balance (cm)) - M(kg)*100)
So a frame with the specs, 340g, 31.5 cm, 320 swingweight, would be .34*31.5*981/(320+(20*.34*31.5)-34) = 21.0
Travlerajm contends that the highest-ranked pros use racquets that cluster around an MgR/I = 21.0, or within 20.8 and 21.2, with women tending to prefer higher values, presumably because their arms are shorter. But there are important outliers, especially on the low end - Nadal is closer to 20 than 21, as was Justine Henin.
But the formula is useful to me because I figured out that all my favorite-swinging racquets were around 21.2 (I'm shorter, so this fits the theory.) And I found that if I matched the MgR/I ratio of two racquets with very different swingweights and balance points that they would both swing with the same feel and timing.
So for me, a racquet with the specs 340g, 31.5cm, 320 swingweight feels very similar to one 350 g, 32.5cm, 330 swingweight. I can switch between them and have little difficulty with timing adjustments, and have found that heavier racquets feel lighter and quicker if they are close to my preferred MgR/I value. Knowing this, I can experiment with heavier and lighter racquets and know that I can get them to swing the way I like them to.
People often find a racquet that they just love, in terms of the way it swings. It feels like it swings lighter than the swingweight would suggest, for example. But they also have this other frame that has the impact feel that can't be beat, but it swings sluggish, or whatever. They wish they could combine the swing feel of the one racquet with the impact feel of the other. If this theory is correct, they can use the MgR/I ratio to tune the frame with the great impact feel so that it has the same sweet swing feel of the other one.
But opinions on the value of this thing vary. Who knows? I did notice that the average MgR/I of nearly the entire range of Head's new IG line (the Prestiges in particular) increased by about .2 as compared to the older Youtek line.