Polarization, Recoil Weight & MgR/I demystified?

[Brando]

Recoil weight, the polarization index, and MgR/I are different measures of racquet polarization calculated from the same variables of weight, balance & swingweight (SW):

THE FORMULAS:
Recoil Weight = SW - (wt. in kg. x (cm balance - 10)²)
The Polarization Index = Recoil Weight ÷ Weight in grams
MgR/I = (wt. in kg x 980.5 x cm balance) ÷ (SW + (20 x kg wt. x cm balance) - (100 x kg wt.))

THE IDEAS
Recoil Weight is like swingweight except its axis is the balance point instead of 10cm (your hand). The higher the RW, the more polarized the frame: >170 is very polarized; <150 is very depolarized.
The Polarization Index looks at RW in proportion to mass to arrive at a simpler polarization measure: most racquets hover around 0.50 PI, with > 0.50 PI being more polarized and <0.5 PI being less polarized.
MgR/I is used to adjust how quickly the hoop comes through your swing so as to fit arm length and swing style by varying weighting and its positioning to achieve your ideal racquet head lag. (The higher the MgR/I, the less polarized the frame and the faster the hoop comes through.) <20 is very polarized; >21.5 is very depolarized.

It’s easy to assume that these measures move consistently visa vie one another, as if a lower recoil weight means a less polarized frame, and so, a higher MgR/I every time. While this is mostly true, it’s not the hard n’ fast rule people think. As you’ll see from the case of Andrey Rublev’s racquet customization, there are differences among the three polarization measures that are easy to miss and quite confusing, too, unless you dive a bit deeper:

Rublev’s Racquet vs. its stock specs*	In Year	Length [cm]	Weight [grams]	Balance [cm]	Swing Weight	Recoil Weight	Polariz’n [RW/Wt]	MgR/I
Stock Gravity Pro	2018	68.6	332	32.0	332	171.3	0.52	20.37
Rublev’s Gravity Pro	2019	68.6	359	31.0	335	176.7	0.49	20.92

* All specs are strung specs, as they will be throughout this post.

Rublev’s racquet tech adds 20.4 grams around 16cm up the handle, probably in the form of gobs of silicon, plus 1.6g of tape at 10 & 2. Then Rublev adds an overgrip and, after all is stuck n’ done, balance has dropped from 7 HL to 10 HL. Meanwhile, swingweight has risen (barely), and it makes sense because mass added anywhere on a frame increases SW (even if sometimes unnoticeably).

What’s surprising is the rise in RW. I’d think that adding even that much weight that far up a 22cm handle would reduce recoil. But only the polarization index decreases, from 0.52 to 0.49, which doesn’t seem to make sense. How does a mod job lower the polarization index but raise recoil weight when they’re supposed to be the same thing?

Breaking it down, a 5g overgrip increases polarization from 0.5156 to 0.5159 and increases RW from 171.3 to 173.7. OK, that makes sense. What’s less obvious is that the other added weight (a whopping 22 grams of it) rose proportionally more than its distribution raised recoil weight. Indeed, weight increased 8% while RW increased only 3%, making the polarization index fall, by the numbers. This means that if the weight is big enough and/or its distribution is far enough from the poles, then a frame’s polarization index (being a ratio of RW) can drop even as its recoil weight (an absolute value) rises.

Here’s another fun fact. MgR/I rises when weight is added below the balance point but falls from weighting above it. This makes MgR/I different from recoil weight and the polarization index in that it can indicate which end is more polarized.

How exactly does MgR/I change with weight distribution? When weight is added under the buttcap, MgR/I barely rises. From there, the higher up weighting is placed, the more MgR/I increases until mass is placed at the balance point, where MgR/I begins to drop back down. The higher mass is placed above the balance point, the more MgR/I drops, ending up lower than the starting MgR/I. This table displays the phenomenon when 9 grams of weighting is moved up a frame with stock specs of 320g, 33cm balance, 325 SW, and 20.54 MgR/I:

9g AT VARYING LOCATIONS	butt	handle	b/p	hoop	tip
9-gram Location:​	1 cm	17 cm	33 cm	50 cm	68 cm
Resulting MgR/I:​	20.55	20.73	20.71	20.50	20.07
MgR/I change from 20.54:​	+0.01	+0.19	+0.17	-0.04	-0.47

While I find these patterns fascinating, you might well ask, “Do I really need to know this MgR/I stuff?” The short answer is no, not unless you’re, say, micro-adjusting down the 21.5 MgR/I of your 350g frame for added spin.

‘Truth is, the most popular racquets are between 20.4 and 20.8 MgR/I. Not coincidentally, that’s the standard deviation of 2022’s top-sellers, which average 20.58 MgR/I. In this midrange there are so many combinations of weight, balance, and SW that can reach any one MgR/I that seeking MgR/I as some kind of a benchmark is almost meaningless.

Take Wilson’s Ultra 100 v.4 with its light, very evenly distributed weighting and 4 HL balance. Compare that to Yonex’s Vcore 95 with its heavy-ish, more handle-weighted 7 HL balance. For all their differences, these frames have virtually identical MgR/Is and swingweights:

	of Year	Length [cm]	Weight [grams]	Balance [cm]	Swing Weight	Recoil Weight	Polariz’n [RW/Wt]	MgR/I
Wilson Ultra 100 v.4​	2022	68.6	318	33.0	317	148.8	0.47	20.78
Yonex Vcore 95​	2020​	68.6​	326​	32.0​	316​	158.2​	0.49​	20.79​

‘Think, maybe, such pairings are outliers? Try this one on for size:

	of Year	Length [cm]	Weight [grams]	Balance [cm]	Swing Weight	Recoil Weight	Polariz’n [RW/Wt]	MgR/I
Head Boom MP	2022​	68.6​	315​	32.7​	318​	155.7​	0.49​	20.51
Tecnifibre Tfight RS 305	2020​	68.6​	323​	33.5​	333​	154.9​	0.48​	20.51

So I say, don’t bother with MgR/I if you haven’t already. Get to know your favorite recoil weight instead. It’ll tell you a lot about why some racquets with the same specs can feel “mysteriously” different.

But if you’ve already started down the MgR/I rabbit hole, consider that spec measures are most useful in combination versus targeting some absolute value in any one of them, as some tend to do with MgR/I. Together, specs paint a vivid picture of how a racquet can perform. Learning how to see that in the numbers is fun (to us geeks at least), and getting to enjoy the results on court, the most fun of all.

 

[aaron_h27]

Isn't the whole magic behind the "add lead 7 inches from the buttcap" because you want to raise recoil weight and MGR/I? That's what most people were suggesting for lead placement.

 

[Brando]

True. Are you asking because you think the numbers don't support this view? (If so, the numbers do support it, as we can see from Rublev's customization.)

 

[Tranqville]

@Brando What is your tennis background and how come you know all this?

 

[aaron_h27]

True. Are you asking because you think the numbers don't support this view? (If so, the numbers do support it, as we can see from Rublev's customization.)

Yes your numbers support my statement above I was just wondering how/why they came up with the 7" trick back in the day when racket mod information wasn't widely available like it is now.

 

[travlerajm]

Yes your numbers support my statement above I was just wondering how/why they came up with the 7" trick back in the day when racket mod information wasn't widely available like it is now.

I came up with it because I like the number 7.

 

[jindra]

I came up with it because I like the number 7.

Node.

 

[travlerajm]

Node.

21 also has a nice catchy ring to it.

 

[Brando]

Gah! trav, you just made me spit up my lunch!

 

[Brando]

@Brando What is your tennis background and how come you know all this?

I'm an amateur player and racquet customizer. Nothing special. But I'm a writer and research geek, too. To research polarization I've kinda gone back into the TT archives to read the posts of folks far smarter than me, folks like @travlerajm , who invented the idea of MgR/I as it applies to tennis racquets. @Irvin has some impressive posts on all aspects of polarization (and many other topics, ta boot) and @Ranch Dressing, too. Even as Irvin & Ranch didn't always agree, there's much to be learned from their debates.

Anyway, I began to compile the dribs and drabs of intel I was reading into a database to make sense of it all. I'm not saying I have made sense of it all. I'm only saying I intend to. And I've no doubt that when I (inevitably) get something wrong, they'll correct me.

 

[ryohazuki222]

For those more mathematically inclined, it’s useful to just see the actual equations. Very easy from there to see what’s a function of what else and how a change affects the whole.

cool research though…. Has always been curious about the popular racket specs for RW and mgri but never got around to calculating. Instead, I used atp specs and got benchmarks from there.

 

[Tranqville]

@Brando May I ask you, is there anything special about Babolat Pure Strike Tour 3d Gen MgR/I? Somehow the racquet head comes through so effortlessly, like no other racquet I have tried. I very much wonder if it's possible to replicate that experience in another racquet via customization. I want to experiment with customizing your racquet - Radical MP - to PST's specs.

 

[Brando]

Hi @ryohazuki222. I agree that there's nothing like crunching the #s for yourself to see how this stuff really works. But in terms of communicating the essentials, I've found that too many #s tend to confuse.

 

[Brando]

@Brando May I ask you, is there anything special about Babolat Pure Strike Tour 3d Gen MgR/I? Somehow the racquet head comes through so effortlessly, like no other racquet I have tried. I very much wonder if it's possible to replicate that experience in another racquet via customization. I want to experiment with customizing your racquet - Radical MP - to PST's specs.

something
Yes, that's a special frame in several aspects too numerous to detail here. Most notably, its MgR/I is smack dab on the average that most amateur players prefer. Secondly it has an unusually high twist weight, which gives it nice torsional stability feel on off-center hits.

	Weight [grams]	Balance [cm]	Swing Weight	Twist Weight	Recoil Weight	Polariz’n [RW/Wt]	MgR/I
Babolat PS3G	323	33.0	327	14.8	156.1	0.48	20.58
Head Speed Pro	326	32.5	326	14.3	161.0	0.49	20.56
Tecnifibre 298 Iga	312	33.0	319	15.0	151.0	0.48	20.57
Head Radical 360 MP	312	32.4	324	13.6	167.5	0.54	20.02

I point out the Speed Pro and the Iga ahead of the Radical because I have a philosophy about optimizing frames: Choose one as close to the specs you're after as you can, and make sure that you'll be adding weight to achieve those specs (vs. trying to take weight away unless it's a leather grip). As you can see the Radical is an outlier here.

Don't get me wrong, I looove my Radical 360 MP. But it serves as my perfect platform because I was looking for a polarized outcome around 20 MgR/I. That disclaimer said, I'll say too that the stick I played before optimizing the Radical MP was the PO7, which of course has virtually identical specs to your PS3G.

So if you decide to get the Radical after all, which is currently ridiculously well priced at TW, you could experiment with seeing if you like a more polarized frame (as I did); and if not, move on to depolarizing it into your own personal PS3G clone. The job might be a mite bit more complicated than starting with the Iga but then A) the Iga has no trap door in the buttcap and B) the Radical has an almost identical (parabolic) beam profile to the PS3G, which I have found gives it a very similar power level.

 

[Tranqville]

Thank you for sharing the insight and your approach, @Brando. I think you looked into regular Pure Strike 3G 16x19, not the Pure Strike Tour - while they are similar in many regards, they play very differently, with Pure Strike Tour having the "magic", at least for me, and Pure Strike regular not.

PO7 is highly praised, but does not come in Tour version, unfortunately.
I was considering 300 RS as a platform to "rebuild PS Tour", rather that the 298 Iga you highlighted.

I plan to work with Unstrung Customs on my experiment project: my past attempts at customizing frames on my own were quite a shipwreck.

 

[Brando]

Yes, @Tranqville , silly me. I missed the Tour part. Very different stick indeed!

 

[tele]

@Brando What is your tennis background and how come you know all this?

a lot of this info, along with a calculator, is on the "impacting tennis" website.　like brando, who nicely summarizes(and adds) things here, i also kind of geeked out on the topic and.found that site, alng with some free mechanics textbooks, useful for deciphering what mgr/i is supposed to indicate about a racquet.

 

[Brando]

@tele, you're abso right. ImpactingTennis is an important source of this info and has an amazing page that calculates all the polarization measures if you input weight, balance and SW.

Indeed, I'm not saying anything revolutionary here. It's just that I've noticed the best polarization intel only exists in snippets across multiple sources, so I've never seen it all gathered in one place. This is my attempt to start a space for that. Someone had to do it ‘cause there’s too much confusion. And, if anyone reading this has better intel or different intel that I haven't included, do tell...

 

[Bud]

And the ultimate question... Has implementing all of this knowledge onto your frame improved your success on the tennis court?

 

[travlerajm]

And the ultimate question... Has implementing all of this knowledge onto your frame improved your success on the tennis court?

In my case yes. But it’s not trivial. There is barrier to entry on knowing what you are doing. I’ve been doing this for nearly 20 years, many experiments and 10,000+ hours in my racquet lab, and it’s only the last 5 of those years that I finally started putting all the pieces together and watching my dynamic rating climb.

 

[Djinn]

@Brando So I've read multiple times that aiming for a MgR/I of 21 is best. What's the reasoning behind this? Is there a reasoning behind this?

 

[travlerajm]

@Brando So I've read multiple times that aiming for a MgR/I of 21 is best. What's the reasoning behind this? Is there a reasoning behind this?

The reasoning is that you can beat the dealer.

 

[Brando]

I have a feeling trav is so tired of answering this question that, in travlerajm style, he's reduced it to its essence. So I hope he'll not take offense if I elaborate a bit for those newer to this topic. (And if he does take offense, he's welcome to correct me because he's forgotten more about MgR/I than I'll ever know.)

Testing the formula on himself, travlerajm posted his optimal MgR/I as 21. He said from the get-go that one’s optimal MgR/I changes per arm length and swing style, but he later made the very human mistake of treating his number as an ideal when racquet data indicated that top pros were swinging 21 at the time (2010). [Note: This is my synopsis of a long series of events and posts, and as such the man himself may take exception to it.]

Today's next gen stars average around 20.54 (from the data I've been able to compile). This makes sense because they’re taller and swing much lighter racquets than their predecessors. Regardless, the takeaway for us mortals is that there is no ideal MgR/I for all.

MgR/I is based on the idea that the arm is the upper lever in a double pendulum that 'force couples' with a racquet (the lower lever) that's swing is also affected by gravity. Cutting to the chase, the longer the arm and the more angular the swing path, the more that the racquet head lag you get in a polarized frame will help line up the racquet face to correctly meet the ball in front of you.

So too, the shorter the arm and straighter your swing path, the more a depolarized frame is likely to help you because these frames, by their physics, have less racquet head lag and feel instead like you are pushing a handle vs. pulling a hoop. In other words, these frames 'come through' faster.

All to say, it's useful to know that the longer your arms and the more angular (spin-oriented) your swing path the lower your preferred MgR/I is likely to be (and vice versa for a higher preferred MgR/I).

Phew, I know that's a lot to digest. It's certainly a lot to write. I hope I've done the principle justice.

 

[Brando]

In post #18, I invited others to come along with better ideas and corrections to my OP, and sure enough it's happened. @Irvin informs me that the recoil weight formula constant I used for the hand's position on the racquet (a constant also used in the swingweight formula) should be 10cm, not 10.16cm.

This is just the kind of long-standing discrepancy I was hoping this thread would out. Irvin even knows the origin of the 10.16cm error: It came from Americans describing 10cm to one another as, "It's around 4 inches," which comes out to exactly 10.16cm. Funny how language works: 10cm becomes 10.16 via 4".

Anyway, I'm about to make that correction to the OP so as not to propagate that error which, if you're reading this later, you won't see (but at least you'll know why the OP was later edited).

 

[Irvin]

Also another thing I’ll point out is, for a 27” perfectly uniform racket, the polarization index would be 0.392. If the racket is longer or shorter a uniform racket’s polarization would be different.

You can calculate the inertia of a uniform racket using the formula ml^2/12 then divide by mass to get the polarization index if you’re OCD and concerned about it at all.

 

[Brando]

Ah, I see; at least I think I do. the OP's THE IDEAS section has 0.50 PI as "neutral polarization." But you're saying it's actually at 0.392 PI...?

 

[Irvin]

INHO balance, weight, MgR/I, polarization, polarization index, and recoil weight are way over rated. Weight, balance, and recoil weight are all needed to match rackets. For 27” racket a given weight, balance, and RW combination you can only have 1 MgR/I, and 1 polarization index. I wouldn’t worry about anything but weight, balance, SW, and possibly TW.

 

[Irvin]

Ah, I see; at least I think I do. the OP's THE IDEAS section has 0.50 PI as "neutral polarization." But you're saying it's actually at 0.392 PI...?

seems to me a uniform racket would Be perfectly uniform from butt to tip

 

[travlerajm]

I have a feeling trav is so tired of answering this question that, in travlerajm style, he's reduced it to its essence. So I hope he'll not take offense if I elaborate a bit for those newer to this topic. (And if he does take offense, he's welcome to correct me because he's forgotten more about MgR/I than I'll ever know.)

Testing the formula on himself, travlerajm posted his optimal MgR/I as 21. He said from the get-go that one’s optimal MgR/I changes per arm length and swing style, but he later made the very human mistake of treating his number as an ideal when racquet data indicated that top pros were swinging 21 at the time (2010). [Note: This is my synopsis of a long series of events and posts, and as such the man himself may take exception to it.]

Today's next gen stars average around 20.54 (from the data I've been able to compile). This makes sense because they’re taller and swing much lighter racquets than their predecessors. Regardless, the takeaway for us mortals is that there is no ideal MgR/I for all.

MgR/I is based on the idea that the arm is a double pendulum that 'force couples' with a racquet that's swing is also effected by gravity. Cutting to the chase, the longer double pendulum and the more angular the swing path, the more that the racquet head lag you get in a polarized frame will help line up the racquet face to correctly meet the ball in front of you.

So too, the shorter the arm and straighter your swing path, the more a depolarized frame is likely to help you because these frames, by their physics, have less racquet head lag and feel instead like you are pushing a handle vs. pulling a hoop. In other words, these frames 'come through' faster.

All to say, it's useful to know that the longer your arms and the more angular (spin-oriented) your swing path the lower your preferred MgR/I is likely to be (and vice versa for a higher preferred MgR/I).

Phew, I know that's a lot to digest. It's certainly a lot to write. I hope I've done the principle justice.

Apologies, but I am no longer posting info on racquet physics and customization for performance. I deleted all of my useful threads on this topic last year when I decided to train up and hire a fellow forum poster and start my own business and take a stab at customizing professionally for ATP pros. The public stuff I left behind is mostly just a trail of misleading info.

My business model is that the deliverable is not the racquet, but the improved ranking. That is, I provide a “Level Hop” service for ATP pros. I don’t get paid for the racquet work. I get paid a % of prize money after my client makes it to the top (after the client makes the hop to the next level). No one has ever attempted this before.

We are now in the home stretch of season 1. I took on 1 official client at the start of the season. The results from this season were documented as a daily blog in my Sneak Attack on the ATP Tour thread.

I will be looking to add at least one more official client this off season.

 

[Brando]

Am sad you deleted your best intel from the forum, but I get it and wish you great success in your venture.

 

[Irvin]

Apologies, but I am no longer posting info on racquet physics and customization for performance. I deleted all of my useful threads on this topic last year when I decided to train up and hire a fellow forum poster and start my own business and take a stab at customizing professionally for ATP pros. The public stuff I left behind is mostly just a trail of misleading info.

My business model is that the deliverable is not the racquet, but the improved ranking. That is, I provide a “Level Hop” service for ATP pros. I don’t get paid for the racquet work. I get paid a % of prize money after my client makes it to the top (after the client makes the hop to the next level). No one has ever attempted this before.

We are now in the home stretch of season 1. I took on 1 official client at the start of the season. The results from this season were documented as a daily blog in my Sneak Attack on the ATP Tour thread.

I will be looking to add at least one more official client this off season.

Good luck Travler I wish you and your clients all the best.

 

[Brando]

seems to me a uniform racket would Be perfectly uniform from butt to tip

Yes, I get it now. Thank you. (You're not always the best at explaining things to laymen, Irvin. But you are always accurate, and if said layman bothers to research what you've said, they'll get it.)

 

[El_Yotamo]

Also another thing I’ll point out is, for a 27” perfectly uniform racket, the polarization index would be 0.392. If the racket is longer or shorter a uniform racket’s polarization would be different.

You can calculate the inertia of a uniform racket using the formula ml^2/12 then divide by mass to get the polarization index if you’re OCD and concerned about it at all.

This moment of inertia formula is only right for a thin rod (or rectangular plate). Therefore, even assuming a uniform mass distribution you'd get something slightly different for a tennis racquet because even if you approximate the handle to a rod the rest of the racquet is a different shape. We could get a slightly better approximation if we took the handle to be a rod and the head to be a disk with a hole, and we'd have to forget the throat or perhaps take it to be triangular or something. Either way, it would still be an approximation and we'd need to define a lot more than just the length of the racquet. I just built a super simple/generic racquet prototype on solidworks and had it calculate the inertia tensor, the result is a PI of approximately 0.425 which seems reasonable enough. The main thing is that we can change the inertia tensor by changing the shape without changing the mass of the racquet in the process, which is one of the factors along with the mass distribution itself in racquet design

 

[El_Yotamo]

I'll add a pinch of my own input on here as well... Echoing what @Irvin said I definitely think one should really only worry about the overall spatial mass distribution of the racquet. Now, I've deliberately phrased this parameter in the most general way possible because the mass, balance (COM), SW, RW, and TW all ultimately depend on this. Why?

-The mass is the total sum of little "mass elements" spatially distributed on the racquet
-The balance is the weighted average (with respect to mass) of the "mass elements" spatially distributed on the racquet
-The SW,RW,TW, all represent "how difficult it is to angularly accelerate" in slightly different senses (see below), and are essentially the sum of each little "mass element" spatially distributed on the racquet times the distance squared between that "mass element" and some reference axis:

Now, SW and RW are tied because they are essentially the same parameter relating rotation about different parallel axes (at 10 cm from the base and at the COM respectively), and they are hence also related by the mass and COM. On the other hand, the TW is similar to the SW/RW but represents rotation about an axis which is perpendicular to that of the SW/RW (in mechanics we build a "matrix" which we call the inertia tensor representing all the possible rotations including hybrid combinations). In other words, we have five parameters of which we really only need 3/4.

I've tried very hard to phrase everything such that it can be read by all, if I can improve my explanation lemme know

 

[Irvin]

This moment of inertia formula is only right for a thin rod (or rectangular plate). Therefore, even assuming a uniform mass distribution you'd get something slightly different for a tennis racquet because even if you approximate the handle to a rod the rest of the racquet is a different shape. We could get a slightly better approximation if we took the handle to be a rod and the head to be a disk with a hole, and we'd have to forget the throat or perhaps take it to be triangular or something. Either way, it would still be an approximation and we'd need to define a lot more than just the length of the racquet. I just built a super simple/generic racquet prototype on solidworks and had it calculate the inertia tensor, the result is a PI of approximately 0.425 which seems reasonable enough. The main thing is that we can change the inertia tensor by changing the shape without changing the mass of the racquet in the process, which is one of the factors along with the mass distribution itself in racquet design

As long as the weight is evenly distributed from the butt to the tip it does not matter what the shape is. Any mass any where on the frame’s inertia is determined by I=mr^2. where r is the perpendicular distance to the axis and the frame is not excessively thick.

 

[El_Yotamo]

As long as the weight is evenly distributed from the butt to the tip it does not matter what the shape is. Any mass any where on the frame’s inertia is determined by I=mr^2. where r is the perpendicular distance to the axis and the frame is not excessively thick.

Ok I think you and I are talking about slightly different things. I was referring to an even volumetric mass distribution throughout a racquet, in other words the volumetric mass density is constant. You're talking about just the vertical mass distribution if I've understood right, in other words the linear mass density being constant

Then what we could have written was
I=\int{r^2}dm
For dm=d(ρV)=d(λy)

Where ρ is the volumetric mass density and λ is the linear mass density.

Now if we have a constant-density thin rod (or any object with a uniform linear mass density in the vertical direction) then dλ=0 and λ=m/l and this clearly becomes
dm=λdy=m/l*dy
I=m/l*\int{y^2}dy
I=m/l*2*(l/2)^3/3=ml^2/12
Where we've integrated from -l/2 to l/2 about the COM.

Essentially, by assuming that the mass density is uniform in the vertical direction, we've written λ=m/l and integrated just in the y direction. So for anything other than a thin rod, if λ is uniform ρ cannot be and vice versa. In the former case we get λ=ρA where A is the cross-sectional area of the rod.

 

[Irvin]

@El_Yotamo I was talking about the polarization index of a 27" tennis racket being .392 for a uniform racket. It does not matter to me what the number is for a 27" racket, I could care less if it were 1. A polarization index (as defined) it RW/M. I care about RW and I care about mass, not the PI. I would prefer as few parameters as possible. I see no reason to go beyond mass, balance, any inertia on a parallel axis (RW - SW - I,) and TW.

EDIT: If we want to add a PI parameter (RW/m) why don't we add a Torque parameter (m*bp?)

 

[El_Yotamo]

@El_Yotamo I was talking about the polarization index of a 27" tennis racket being .392 for a uniform racket. It does not matter to me what the number is for a 27" racket, I could care less if it were 1. A polarization index (as defined) it RW/M. I care about RW and I care about mass, not the PI. I would prefer as few parameters as possible. I see no reason to go beyond mass, balance, any inertia on a parallel axis (RW - SW - I,) and TW.

EDIT: If we want to add a PI parameter (RW/m) why don't we add a Torque parameter (m*bp?)

On this we agree for sure haha
I just enjoyed leaning into the concept since they were talking about it

 

[aaron_h27]

MGR/I is not worth worrying about in my experience.

Knowing about twistweight has been very helpful in customizing, more so than SW in my opinion. Especially when purchasing new rackets you kind of know what to expect and where to start with lead.

I think most of us can play with a range of swingweights and this can vary depending on the racket. I don't think people should lock themselves into a SW because it could change depending on the racket you use.

 

[Brando]

We have a consensus. I've enjoyed the exercise of learning about MgR/I. But has it ever helped me optimize a racquet? No. But recoil and twist weight are essential to my manipulations of mass, balance and swingweight. And I can't argue either with @Irvin's point that the polarization index is superfluous intel, too.

 

[aaron_h27]

We have a consensus. I've enjoyed the exercise of learning about MgR/I. But has it ever helped me optimize a racquet? No. But recoil and twist weight are essential to my manipulations of mass, balance and swingweight. And I can't argue either with @Irvin's point that the polarization index is superfluous intel, too.

Yeah discussing MGR/I & Polarization can all get convoluted really quickly. You live and you learn!

 

[Brando]

Yeah, It's funny how a part of my brain gets sucked into polarization discussions like the one @El_Yotamo and @Irvin just had. Does it help me? No. Does it fascinate me that the PI of a uniform 27" stick might be 0.425 or 0.392 depending on whether you're talking volumetric mass density or linear mass density? Geeky as charged!

 

[Grafil Injection]

What would the MGR/I figures be for the following classic sticks:

(i) MAX 200G: 365g, 32.0cm, 350 SW, 16kg TW
(ii) PS85: 355g, 31.75cm, 345 SW, 13.5kg TW
(iii) MaxPly Fort: 370g, 32.75cm, 360 SW, ? TW

Thanks!

 

[Irvin]

What would the MGR/I figures be for the following classic sticks:

(i) MAX 200G: 365g, 32.0cm, 350 SW, 16kg TW
(ii) PS85: 355g, 31.75cm, 345 SW, 13.5kg TW
(iii) MaxPly Fort: 370g, 32.75cm, 360 SW, ? TW

Thanks!

MgR/I = (wt. in kg x 980.5 x cm balance) ÷ (SW + (20 x kg wt. x cm balance) - (100 x kg wt.))

I have no idea what your 16 kg and 13.5 kg numbers represent, certainly it’s not twist weight Which is not used in calculation of MgR/I.

 

[tele]

What would the MGR/I figures be for the following classic sticks:

(i) MAX 200G: 365g, 32.0cm, 350 SW, 16kg TW
(ii) PS85: 355g, 31.75cm, 345 SW, 13.5kg TW
(iii) MaxPly Fort: 370g, 32.75cm, 360 SW, ? TW

Thanks!

plugged into impactIng tennis calculator mentioned above (quickly, so please dbl check values)
i. 20.93
ii. 20.66
iii. 21.02

 

[Brando]

Your values are correct, @tele, and they provide a nice platform for what we were just discussing. What do those MgR/Is reveal about these classic frames? No, I’m really asking.

All I can gather from the MgR/Is is that a greater proportion of the considerable weight in the 200G and the Fort, especially, is in the handle. (But then I kinda already guessed that from the sheer mass of these beasts.) The high MgR/Is also indicate that, more likely than not, these are depolarized frames, with the PS85 being likely the most polarized of the three. But how polarized is anyone’s guess. With this much mass involved, it could be fairly evenly distributed along the frame (as suggested by the higher MgR/Is) or placed more toward the ends.

But if I know the recoil weights…
MAX 200G: 365g, 32.0cm, 350 SW, 173.3 RW
ProStaff 85: 355g, 31.75cm, 345 SW, 177.1 RW
MaxPly Fort: 370g, 32.75cm, 360 SW, 168.5 RW

…I know that my depolarized guess couldn’t have been more wrong. Indeed these sticks are classics for a reason. Any recoil in the 170s is a perfectly polarized frame. This tells me that, despite their heft, their weight is very efficiently distributed where needed: near the hitting point (to add ball speed) and near the butt (for added inertial stability). And between these two points there’s scant dead weight to slow my swing down any more than a 350-360 swingweight already has to. Now I'm all Sir Mix-A-lot about that PS85 and her ample 177 recoil...

 

[Brando]

Hi @galapagos, I couldn’t agree more with your point over at the Tecnifibre T-Fight ISO thread that there are many factors beyond the ‘Big-3’ specs of weight, balance, and swingweight that make a racquet feel right in the hand.

Still, you asked if there was any correlation in recoil weight (as a product of the big-3) among the racquets you’ve played with. Well, let’s see. Here’s your list plus the racquets’ stock strung recoil weights added by me in bold text…

1. Head 360+ Speed Pro (amazing) [161 RW]
2. Head Graphene Speed Pro (your starting racquet from 2013) [177 RW]
3. Wilson Blade 18x20 from 2015 (great feel but messed up my wrist) [153 RW]
4. Head Radical MP 360+ (very well balanced distribution) [157 RW]
5. Head Gravity Pro (felt heavy enough, fast enough but not enough plow) [150 RW]
6. Tecnifibre Tempo IGA (again, i was surprised how good it felt swinging) [154 RW]
7. Head IG Prestige MP (magic wand) [155 RW]
8. Wilson Pro Staff 95 S (magic wand) [146 RW]
9. Yonex Ezone DR (lacked stability but the swing style was cool) [160 RW]
10. Diadem Elevate FS 98 v2 (lacked power but feel was magic wand) [164 RW]
11. Tecnifibre ISO 305 18x19 [164 RW]
12. customized Angell TC95 at 320g, 30,8 cm, 295 SW unstrung (probably the closest middle-man between stable rocks and magic wands) [163 RW]

What jumps out immediately is that these recoil weights are pretty wide ranging; but then so are the specs of these frames, including varied string patterns and beam widths, etc. Hazarding a guess, I’d say you’ve not found your huckleberry. Or maybe you have, but the search has been so much fun, you can’t stop?

Either way, if we knock out the highest and lowest [177 and 146 being singular outliers] and your frames that in one way or another felt lacking, your sweet spot becomes 154 -157 RW. This is actually a pretty narrow range. And it’s a fertile one given that the average top 20 selling racquet is 158 RW, with a standard deviation of 7 kg*cm².

So what does 154 -157 RW mean? It’s a tick on the ‘depo’ side of the median between polarized and depolarized frames. It also suggests that you’re likely around average height and that your stroke mechanics lean toward the feel of pushing a frame through contact vs. pulling it (behind your hand). It also explains why you’re drawn toward foam filled frames like Tecnifibre's.

Anyway, @galapagos, I hope this helps. And if not, don’t be afraid to tell me how wrong I am because there are many exceptions to these ‘rules.’

 

[Shroud]

And the ultimate question... Has implementing all of this knowledge onto your frame improved your success on the tennis court?

Kind of. First off I don’t know. Actually calculate it out but I use the concepts the tennis racket by feel. This allows me to pretty much take any frame and in a short period of time get it where it needs to be to feel good. I would improve my tennis more if I could do the same thing for my knees. I wish I could add some lead to my meniscus…

pretty much just mess with the MgRI stuff and for what it’s worth 20g of lead can be put into 7 inch point. It will stick out for sure but you can hide it with tape if you want.

 

[galapagos]

Hi @galapagos, I couldn’t agree more with your point over at the Tecnifibre T-Fight ISO thread that there are many factors beyond the ‘Big-3’ specs of weight, balance, and swingweight that make a racquet feel right in the hand.

Still, you asked if there was any correlation in recoil weight (as a product of the big-3) among the racquets you’ve played with. Well, let’s see. Here’s your list plus the racquets’ stock strung recoil weights added by me in bold text…

1. Head 360+ Speed Pro (amazing) [161 RW]
2. Head Graphene Speed Pro (your starting racquet from 2013) [177 RW]
3. Wilson Blade 18x20 from 2015 (great feel but messed up my wrist) [153 RW]
4. Head Radical MP 360+ (very well balanced distribution) [157 RW]
5. Head Gravity Pro (felt heavy enough, fast enough but not enough plow) [150 RW]
6. Tecnifibre Tempo IGA (again, i was surprised how good it felt swinging) [154 RW]
7. Head IG Prestige MP (magic wand) [155 RW]
8. Wilson Pro Staff 95 S (magic wand) [146 RW]
9. Yonex Ezone DR (lacked stability but the swing style was cool) [160 RW]
10. Diadem Elevate FS 98 v2 (lacked power but feel was magic wand) [164 RW]
11. Tecnifibre ISO 305 18x19 [164 RW]
12. customized Angell TC95 at 320g, 30,8 cm, 295 SW unstrung (probably the closest middle-man between stable rocks and magic wands) [163 RW]

What jumps out immediately is that these recoil weights are pretty wide ranging; but then so are the specs of these frames, including varied string patterns and beam widths, etc. Hazarding a guess, I’d say you’ve not found your huckleberry. Or maybe you have, but the search has been so much fun, you can’t stop?

Either way, if we knock out the highest and lowest [177 and 146 being singular outliers] and your frames that in one way or another felt lacking, your sweet spot becomes 154 -157 RW. This is actually a pretty narrow range. And it’s a fertile one given that the average top 20 selling racquet is 158 RW, with a standard deviation of 7 kg*cm².

So what does 154 -157 RW mean? It’s a tick on the ‘depo’ side of the median between polarized and depolarized frames. It also suggests that you’re likely around average height and that your stroke mechanics lean toward the feel of pushing a frame through contact vs. pulling it (behind your hand). It also explains why you’re drawn toward foam filled frames like Tecnifibre's.

Anyway, @galapagos, I hope this helps. And if not, don’t be afraid to tell me how wrong I am because there are many exceptions to these ‘rules.’

Thank you for your time and effort. That's cool to know. Of course what worries me is the fact that quality control can shift things around. How sensitive is the RW? Pretty much within the quality variances or it can jump around like crazy? Only my Angell is a known spec. Rest is just estimated based on advetised specs. TC95 was the frame I played the longest. Decided to move on in search for something more forgiving with also slightly more control (launch) but similar traits.
I was messing up with my customized angells a lot. Tried soo many specs and really found something that was "easy" enough on my forehand and stable/heavy enough on my backhand.

I should have mentioned that my "magic wands" in case of IG Prestige MP and Wilson Pro Staff95 S was to add even more weight to the handle. If i remember it right (it was like 10 years ago) I added like 15 grams across the handle resulting in around 360g frame (with strings) and balance around 31cm strung. It was heavy enough on my backhand and whippy enough on forehand with enough plow through but mainly through static weight rather than swing weight. I remember having a blaster TC95 320g/310cm/305 SW unstrung and after adding like few more overgrips it suddenly clicked. Static around 360g strung 31cm strung but quite heavy SW. My technique was working with those specs BUT my body couldn't handle it (it was too dangerous on my shoulder coz I don't do enough stabilization excercises).

I'm not sure what's the average height. I am 186 cm. I believe this might be slightly above. Quite long arms. On the second comment I agree that my technique leans towards the feel of pushing through contact.

Did you measure ISO with my mentioned customization? In that case I probably could narrow my top RW between 159-164. I really felt dialed in (technique and feel of the movement) swithing between my Angell and Speed Pro so there is something in this theory as according to your graph they should feel similar in swing.
I first added more weight to the handle of ISO 18x19 but decided to remove it since it felt like not suiting the frame. Trying to figure it out since the balance point is not exactly what I am used to (usually strung around 31.5 - 32) but playing with all the different numbers around seems to change the overall feel which of course makes sense.

 

[Brando]

Did you measure ISO with my mentioned customization?
I first added more weight to the handle of ISO 18x19 but decided to remove it since it felt like not suiting the frame. Trying to figure it out since the balance point is not exactly what I am used to (usually strung around 31.5 - 32) but playing with all the different numbers around seems to change the overall feel which of course makes sense.

No, I didn't, @galapagos. So I just did; and adding 10g under the butt cap of your ISO 305 (assuming it's on-spec) takes the recoil weight from 164 to 175, which is ideally polarized. I too am 189cm tall (6'1"), and my frames, customized to 174 RW (and 338 SW, too BTW), feel perfect to me. All to say, you might want to give yourself a little more time with that setup. Given the length of your arm, it should feel quite good and similar to your 2013 Graphene Speed Pro. If so, the question becomes, is that a feel you were attempting to recapture in other sticks or one you were trying to get away from?

And to answer your other question, recoil weight is as 'sensitive' as are the 'Big-3' specs it's calculated from. If they vary widely from spec, then recoil will too. I've found Tecnifibre racquets to be fairly close to spec. But the only way to know for sure is to measure for yourself or have your local tennis/pro shop measure for you.