The essence of racket customization

In this chapter, I’ll go over the most important principles of racket modifications. I’ll go over the guides for customization and the effects of parameters on one’s tennis game. People often say that they just want to know which parameters to change in order to achieve the desired effect. Well, here you go.

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AIM – Average Impact Mass

  1. AIM quantifies the racket’s ability to give a player the desired outcome after the ball leaves the string bed. or the ability to dominate the contact.
  2. AIM is a hybrid of swingweight and twistweight, that also considers the area of the impact.
  3. Higher AIM means a higher racket ceiling given the same racket head speed.
  4. Higher AIM gives the player a better ability to dominate the contact with the ball on ground strokes, on the larger area of the string bed.
  5. Higher AIM means the racket is less manoeuvrable.
  6. AIM is the best measure of racket stability during contact.

Mass, Balance and MR^2

  1. First one should be obvious, a heavier racket can generate more ball speed/power, provided we can swing it with the same swing speed through the contact point.
  2. For any serious player, the balance should be around or bellow even (34,3 cm) and above 31 cm.
  3. Generally, you can compensate for the lack of weight with a more »head heavy« racket and vice versa.
  4. For a great two-handed backhand, you need a balance of 32,5 cm or more, but than the balance starts causing problems on the forehand side. This is for a simple reason, that we hold the racket higher up the handle with both hands and thus shift the pivot point higher, lowering the effective racket balance and dynamic weight (swingweight).
  5. Having a one-handed backhand makes it easier to optimize the mass and balance for both wings because the pivot point is the same with both strokes. Pro players with one-handed backhand and more »head light« rackets (Federer, Wawrinka, Shapovalov) can usually hit exceptional shots from both sides. And then there is someone like Grigor Dimitrov, who is the complete opposite of this theory. He has a more »head heavy« setup, and a one-handed He compensates heavily with his athleticism and doesn’t get any help on his shots from the racket, and that’s why I believe with this kind of setup, he will never be on the top of the mens game.
  6. More »head light« rackets are better for the serve and just about any shot with 1 hand.
  7. MR^2 is useful, to determine the limitations of the player or. how much weight leveraged by distance R can the player handle. This is based on players strenght, stamina and what the joints can handle.

Swingweight

  1. High swingweight smoothes out the strokes and it makes almost impossible to just arm the ball with bad technique. That is because the racket has a higher moment of inertia and you have to generate more momentum with your hand to get it moving and small deviations of your hand movement and muscle action don’t affect the racket head position and path so much.
  2. Derived from the first point this translates to less maneuvrability and longer reaction times for volleys etc.
  3. Higher swingweight usually means lover MGR/I and that gives you the feeling that you are dragging the racket through the contact, and not pushing it. It gives you the feel of carving around the ball and giving you more control.
  4. More control and consistency also comes from the fact that with a higher swingweight you can swing at lover swing speed to get the same amount of power and spin.
  5. High swingweight also means you need longer strokes to accelerate the racquet. Think about Rafael Nadal and Alexander Zverev (Novak Djokovic is also here but not so extreme). They both have hight swing weight and low MGR/I, and they have long strokes, especially on the forehand side, and they play with incredible control and consistency. On the other side of the spectrum is, for example, Nick Kyrgios. Low swingweight, hight MGR/I, short strokes, incredible racquet head acceleration but a lack of consistency, because when he get’s tight, the slightest deviations in his stroke mechanics cause a much bigger change in the racquet head position at contact. On the other hand, Nadal and Zverev when they get tight their only job is to get the racket through the contact and the ball goes in. They spend much more energy doing that, but they can go in the »lockdown« mode and not miss.
  6. I generally advocate that players use as high of a swingweight they can play with, but without mistiming the ball when the matches get longer. It’s important to know your limits because a higher swingweight won’t be beneficial if it tires you or you can’t accelerate the racket enough before the contact.
  7. Higher swingweight is less forgiving and requires you to have better footwork, because of the longer strokes. Your positioning has to be better because you can’t make quick adjustments to your swing path.
  8. Higher swingweight can mean more spin (again if you can swing it). The racket has more angular momentum during the contact consequently more kinetic energy in the vertical direction, which means strings can move more and snap back, and impart more spin on the ball. Also, more angular momentum at impact means less deformation of the racket and more energy can be transferred to the ball (rotational and kinetic energy).
  9. Rackets with higher swingweight have a higher ceiling in a perfect world. Humans are not perfect machines in a perfect world, so we need to compromise and making compromises is the real artistry of racket modifications. That’s also where MGR/I comes in to play, which is basically a measure of compromise between mass, swingweight and balance.

Twistweight

  1. High twistweight is good for blocking and pushing the ball around. It requires a more linear swing path and is more forgiving and less maneuvrable. You might benefit from such rackets if you don’t hit the ball cleanly, have bad timing etc. or you have a more linear swing style or the so-called WTA strokes. Women on the tour usually have a more linear swing path and make the racket drop on the edge, and the racket continues in that position all the way to the contact.
  2. Low twistweight means more manoeuvrability, which means you can perfect your strokes, you can quickly adjust the racket face position, you can hit »whippier« shots and it rewards good technique, and clean ball striking.
  3. Low twistweight means you can increase the swingweight and still have a maneuvrable racket.
  4. Low twistweight is less forgiving and it requires more concentration, better footwork and in general more effort to play well with.
  5. In a perfect world a racket with a low twistweight and a higher swingweight has a higher ceiling, but again one should build the ceiling for his own abilities.

Recoilweight and Polarization

  1. A racket with a high recoilweight will feel more stable on contact, be more arm friendly, and won’t feel so stiff.
  2. Polarization and recoilweight go hand in hand. For a light racket to have a high recoilweight, we need a high level of polarization and vice versa.
  3. A polarized racket will give you a feel of dragging the racket through contact point and a depolarized one will feel like you are pushing the racket through the contact.
  4. Polarized rackets are good for spin production, but are harder to use, are less forgiving and offer less depth control.

MGR/I

The weight, swingweight and balance all play a certain role, but when it comes to swing path, stroke mechanics and timing the ball, MGR/I is the most determinental.

High MGR/I

  1. Stroke mechanics feel like you are pushing the racket through the contact point instead of pulling it,
  2. Racket offers better depth control and feel for the ball,
  3. It is easier to hit the ball early and in front of the body.
  4. The balls penetrate the court more and don’t have a loopy trajectory, and if the mass is sufficient, the shots still have a lot of spin,
  5. Players with more »open« forehand grip (like eastern or even continental), can benefit more from a high MGR/I on the forehand side,
  6. It’s easier to time the ball well, especially in high-pressure situations and when you tighten up.

Low MGR/I

  1. Stroke mechanics feel like you are pulling the racket through the contact point instead of pushing it,
  2. Racket offers better feel for curving around the ball instead of hitting through it (think Zverev forehand),
  3. It is harder to hit the ball early and in front of the body. 
  4. It’s easier to play »safe tennis« with just looping and spinning the ball, but harder to control direction and depth,
  5. In contrast to high MGR/I – harder to time the ball in high pressure situations and when you tighten up.
The overall ceiling of the racket might be higher with a lower MGR/I, but that doesn’t really help you to win matches if you can’t execute. Always strive to be Antifragille (read this article on Antifragille).

Disclaimer: These are not hard scientific facts, but rather findings of an empirical skepticist. 

Strings

I suggest you read the whole chapter on strings, because it’s a bit harder to break it down like I have done with other parameters.

On this web page, you can see a lot of pictures and examples of calculations made in our Excel spreadsheet calculators. You can get access to them by subscribing to Impacting Tennis tools here. You will receive a confirmation mail and after your subscription is revised, you will receive a file containing:

-Customization calculator

-Swingweight calculator

-MGRI/, Polarization, Recoilweight calcualtor

-AIM and Effective mass calculator

-Extended racket calculator

-String weight database

-Pro player’s specifications database

-And more