Category Archives: Accuracy
Let’s Get Serious!
If you listen to the Racquet Quest podcasts you will recognize this statement!
So, why are we posting it on the website if it is already a podcast? Because it is serious! A racquet came in today that reminded me of why we started GASP! The stringing is so awful that I can’t keep myself from writing this!
The owner of the racquet does not remember at which tournament it was strung otherwise we could contact them and offer some suggestions!
Why is this racquet so bad?
- Inconsistent tension across the string bed
- The accuracy index is 65!
- Virtually no tension in the top cross string…because
- The racquet was strung from the bottom up plus the poor knot
- Stringing of the crosses started at the bottom (starting X at the top is highly recommended)
- Tie offs on the wrong holes
- 8M is better
- Cross over at the lower side
- Probably due to the wrong tie off
- One-piece format
- Inconsistent string tension
- Bad tie off knots
Why is it so hard to do a better job when stringing a tennis racquet? In this case, it appears the stringer has no training. There are errors no competent stringer would make! But, until players refuse to accept this shoddy work it will continue!
- Wrong Tie Off Hole
- Cross Over
- Bad KNot
- Another Really Bad Knot
- No Tension on the First Cross String
String Tension Testers…Friend or Foe?
The StringMeter is a device used to check the tension of an individual string. There are other versions of similar functionality, but this is what we use, and I will start with that.

Interestingly, this device traces its design to a tool that is used to check mainstay tension on a sailing vessel.
It is clear that our devices are well used, so they must be a “friend,” not a “foe”! And to that, I would say yes! The two (2) units shown here are “calibrated” units. One device is “free string,” and the other is “strung string.” These are different scales and very important for accurate information.

String Tension Tester
When we evaluate string or stringing machines, one of the most important values is the string tension with only the main strings installed. Using the “free string” scale, we check every main string and record the number.
Once the racquet is fully strung, we can check some center main strings and center cross strings with the “strung string” scale and see the variation. The difference between the two is the “natural ratio” of the racquet.
In addition to the stringing machine review use of the StringMeter, we also use it to calculate our “accuracy index.”
For this, we use the “strung string” scale and check each main string tension from left to right and every cross string tension from top to bottom and compare the actual numbers to the calculated numbers based on a non-distorted racquet. This spreadsheet shows how accurately the ball will come off of the racquet face.
The “efficiency index” tells us how much the racquet needs to change shape to reach that “index.”
These are all essential functions of the StringMeter and String Tension Tester from Gamma Sports.
But, what if the StringMeter or other device is used without knowing what it is telling the user?
This is the “foe” part!
This would be the case if a customer with such a device has a racquet strung at say a reference tension of 55 pounds. The customer then uses the method to check the tension and finds that it is not 55 pounds or even close! The customer is not going to be happy!
If the customer knows what to do, they can check the main string tension as soon as they can after stringing, then, later on, to see how much the string has stretched without regard to the reference tension.
It is what it is!
When the racquet is no longer performing it would tell the customer how much the tension can deteriorate before stringing is required.
So, these devices are very useful for individual string tension but no so much for “string bed stiffness,” which is the total string bed as a ball impacts it.
We will look at some of the “string bed stiffness” devices in a future post.
Head Graphene 360+ Speed MP Lite
The Head Graphene 360+ Speed MP Lite may be the perfect racquet for a player looking for a thin(er) beam, 100 square inch head size, slightly lighter than most MP racquets!
As you will see in the specifications this racquet is about 28 grams (1 ounce) lighter than the MP model, and, just a little more flexible, or better said, less stiff!
Forty-nine point nine percent (49.9%) of the total weight resides toward the head of this racquet, so if you think in terms of “points” it is 0.16 points head light.
Some customization will make this a racquet that you can stay with for a long time. As your skills advance, so can the racquet!

Head Graphene 360+ Speed MP Lite
As I am working on this post I realize how much trouble it is to switch between racquet reviews for comparison so I am including a link to the Head Graphene 360+ Speed Series Comparison.
| Manufacturer | Head |
|---|---|
| Racquet Model | Head Graphene 360+ Speed MP Lite |
| Reference Tension | 56 lbs - 25.4 kg |
| String | Victrex PEEK fiber Experimental 7718 |
| Machine Used | True Tension Professional |
| ASPS, RDC | 51 |
| ASPS, FlexFour | 62 |
| Racquet Flex, RDC | 60 - After stringing |
| Racquet Flex, FlexFour | 49 |
| Weight, Grams | 293 |
| Weight, Ounces | 10.34 |
| Balance, mm | 342 |
| Balance, Inch | 13.46 |
| Length, Cm | 68.5 |
| Length, Inch | 26.97 |
| Head Width | 9.68 |
| Head Length | 13.06 |
| Head Area, cm2 | 640.8 |
| Head Area, Sq. Inch | 99.3 |
| Beam Width, mm, Shaft, Center, Tip | 23, 23, 23 |
| In Plane Stiffness, Pounds/In | 307.3 Lbs/In. |
| In Plane Stiffness, Kg/cm | 139.4 Kg/cm |
| Number of Main Strings | 16 |
| Number of Cross Strings | 19 |
| Ratio Cross/Mains | .624 |
| Main String Grid | 7.30 |
| Cross String Grid | 10.62 |
| Density (% of head filled with string) | .780 |
| Average Cross String Space | .559 |
| Average Main String Space | .456 |
| Dynamic Tension, Kp, ERT | 35 |
| Dynamic Tension, Lbs/in | 195.76 |
| First Moment, Nm | .782 |
| Polar Moment | 323 |
| Torsional Stability | 15 |
| Swing Weight, Kg/cm2 | 308 |
| Swing Weight, Ounces | 10.86 |
| Swing Weight Calculated | 342.7 |
| Power, RDC | 46 |
| Control, RDC | 57 |
| Manueverability, RDC | 81 |
| Power, Calculated | 1835.6 |
| Head Points | 0.16 (negative = head heavy) |
| Head Weight, % | 49.9% |
| Center of Percussion | 21.0 |
| Dwell Time, ms, No Swing | 8.91 |
| Efective Stiffness - lbs | 27.6 |
| K, Lb/In (SBS) RDC | 163.46 |
| Recoil Weight | 138.67 |
| Twist Weight | 205.8 |
| End Weight | 105.8 |
| Tip Weight | 186.5 |
| 9 O'Clock | 95.1 |
| 3 O'Clock | 94.5 |
| Butt Cap | 103.0 |
Head Graphene 360+ Speed S
I think we all know what “Pro and MP” mean but what about “S”? I am not sure, so we are going to call it “Special”!
The Speed S is indeed special and probably one of the best all-around racquets for 2020! You will see by the specs why this may be the case but a couple of things stand out. A 100 square inch head size. A uniform 16×19 string pattern and 25mm beam producing the stiffness of RDC 64!
The overall weight and swing weight are just right for most advancing players and can be modified when the need arises! This is really a “players” racquet in disguise!

Head Graphene 360+ Speed S
While I was doing this post I realized how difficult it is to switch between racquet reviews to see a comparison so here is a link to the Head Graphene 360+ Speed Series Comparison.
| Manufacturer | Head |
|---|---|
| Racquet Model | Head Graphene 360+ Speed S |
| Reference Tension | 56 lbs - 25.4 kg |
| String | Victrex PEEK fiber Experimental 7718 |
| Machine Used | True Tension Professional |
| ASPS, RDC | 54 |
| ASPS, FlexFour | 67.5 |
| Racquet Flex, RDC | 64 - After stringing |
| Racquet Flex, FlexFour | 40 |
| Weight, Grams | 302 |
| Weight, Ounces | 10.44 |
| Balance, mm | 328 |
| Balance, Inch | 12.91 |
| Length, Cm | 68.5 |
| Length, Inch | 26.97 |
| Head Width | 9.68 |
| Head Length | 13.06 |
| Head Area, cm2 | 641.2 |
| Head Area, Sq. Inch | 99.3 |
| Beam Width, mm, Shaft, Center, Tip | 25, 25, 25 |
| In Plane Stiffness, Pounds/In | 425.2 Lbs/In. |
| In Plane Stiffness, Kg/cm | 192.8 Kg/cm |
| Number of Main Strings | 16 |
| Number of Cross Strings | 19 |
| Ratio Cross/Mains | .624 |
| Main String Grid | 7.35 |
| Cross String Grid | 9.40 |
| Density (% of head filled with string) | .749 |
| Average Cross String Space | .539 |
| Average Main String Space | .453 |
| Dynamic Tension, Kp, ERT | 37 |
| Dynamic Tension, Lbs/in | 206.94 |
| First Moment, Nm | .764 |
| Polar Moment | 312 |
| Torsional Stability | 16 |
| Swing Weight, Kg/cm2 | 296 |
| Swing Weight, Ounces | 10.44 |
| Swing Weight Calculated | 324.9 |
| Power, RDC | 45 |
| Control, RDC | 57 |
| Manueverability, RDC | 89 |
| Power, Calculated | 1880.4 |
| Head Points | 4.57 (negative = head heavy |
| Head Weight, % | 47.9% |
| Center of Percussion | 20.9 |
| Dwell Time, ms, No Swing | 8.66 |
| Efective Stiffness - lbs | 29.3 |
| K, Lb/In (SBS) RDC | 173.08 |
| Recoil Weight | 141.20 |
| Twist Weight | 211.83 |
| End Weight | 119.7 |
| Tip Weight | 182.9 |
| 9 O'Clock | 94.2 |
| 3 O'Clock | 94.2 |
| Butt Cap | 113.0 |





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