🎾 The Science of Tennis Strings – Complete Guide with UNI‑CORD®

Strings are often called the “engine” of a tennis racket. Yet most players choose them based on habit or brand reputation rather than a rational, data-driven approach.

At TennXpert, and through our collaboration with UNI‑CORD®, we bring science to string selection: string stiffness, gauge, tension, energy return, and how these factors directly impact spin, power, comfort, and control.

Here’s the ultimate guide to understanding your strings—and why UNI‑CORD®’s range offers the most logical way to choose the perfect setup.

1. Key Physical Parameters of a String

1.1. Stiffness (Stringbed stiffness)

• Definition: The resistance of a string to deformation (measured in kg/mm or N/mm).

• Effect on playability:

  • Higher stiffness → more control, lower dwell time, less comfort.

  • Lower stiffness → more comfort and power, but reduced directional accuracy.

💡 UNI‑CORD example:

• THE BLOCKER V3 1.30 → firm and stable.

• THE TOUCH PLAYER V2 1.25 → soft and arm-friendly.

1.2. Gauge (diameter)

• Thinner gauge (e.g. 1.20 mm): more spin, more feel, less durability.

• Thicker gauge (e.g. 1.30 mm): more control, longer lifespan, slightly reduced spin potential.

💡 UNI‑CORD example:

• THE KILLER V2 1.20 → explosive spin and power.

• THE BLOCKER V3 1.30 → control and durability.

1.3. Tension

• Definition: The pulling force applied during stringing (kg or lbs).

• Effect:

  • Higher tension → firmer stringbed, more control, less trampoline effect.

  • Lower tension → more power, comfort, and dwell time.

⚡ Tension loss formula:

Effective tension ≈ Initial tension × (1 – tension loss %)

Polyesters often lose 10–20% tension within hours; multifilaments lose less.

💡 UNI‑CORD example:

• THE UNIVERSAL 1.35 (multifilament): minimal tension loss.

• THE STRONGER V2 1.25 (poly): expected 12–15% tension loss.

1.4. Stringbed deflection (power index)

Power is related to stringbed stiffness and dwell time. Lower stiffness and longer dwell time transfer more energy to the ball.

📌 Formula approximation (simplified):

Power ≈ 1 / √(Stringbed stiffness)

2. The UNI‑CORD® Scientific Range

UNI‑CORD® simplifies the string world by offering a targeted lineup, each named after its core performance trait:

Model	Type	Gauge	Profile	Key Feature
THE UNIVERSAL 1.35	Multifilament	1.35	Round	Comfort & all-round
THE PUNCHER 1.30	Poly	1.30	Round	Power + control
THE EXPLOSIVE 1.30	Poly	1.30	Soft	Power + comfort
THE KILLER V2 1.20	Poly	1.20	Thin	Spin & power
THE POWERFUL V2 1.24	Poly	1.24	Round	Controlled power
THE STRONGER V2 1.25	Poly	1.25	Round	Spin-friendly
THE TOUCH PLAYER V2 1.25	Poly Soft	1.25	Soft core	Arm comfort
THE SPINNER V2 1.25	Poly	1.25	Twisted	Maximum spin
THE STRIKER V2 1.24	Poly	1.24	Round	Balanced performance
THE CLASSICER V2 1.30	Poly	1.30	Round	Firm control
THE BLOCKER V3 1.30	Poly	1.30	Round	Stability
THE GUT V2 1.31	Natural gut	1.31	Round	Premium feel (preorder)

3. Formulas for Rational String Selection

3.1. String stiffness calculation

String stiffness depends on tension (T) and gauge (d):

Stiffness ∝ T / d

• Increasing tension or using a thicker string → more stiffness.

💡 Practical example:

• 25 kg with 1.25 mm → stiffness index X

• 25 kg with 1.20 mm → ~4% less stiffness (more comfort and spin)

3.2. Hybrid stringing: combining materials

When mixing two string types:

Hybrid stiffness ≈ (Mains stiffness + Crosses stiffness) / 2

• Soft crosses (e.g. THE UNIVERSAL) reduce harshness.

• Stiffer mains (e.g. THE SPINNER V2) keep control and spin.

3.3. Tension matching across frames

If two rackets have different swingweights or head sizes:

Adjusted tension = Base tension × √(Reference SW / Actual SW)

This keeps stringbed response consistent across your rackets.

4. Choosing Strings Scientifically

4.1. By player profile

• Comfort-first (arm issues): THE TOUCH PLAYER V2 or THE UNIVERSAL

• Spin and power: THE SPINNER V2 or THE KILLER V2

• Control and precision: THE BLOCKER V3 or THE CLASSICER V2

• Hybrid setups: THE UNIVERSAL (cross) + THE STRONGER V2 (mains)

4.2. Recommended tension ranges

Style	Tension
Spin-oriented	22–23 kg
Power-oriented	21–22 kg
All-round	23–24 kg
Comfort/arm care	20–22 kg
Control-heavy	24–25 kg

5. Why UNI‑CORD® + Certified Stringers Matter

UNI‑CORD® pairs its scientifically designed strings with a network of certified stringers, ensuring:

• Accurate tensioning.

• Professional knots and installation.

• Personalized guidance based on playing style.

📍 Find your certified stringer on the UNI‑CORD® map.

6. Pro Tips for Advanced Players

• Measure tension loss with a tension meter to track consistency.

• Log every string job (tension, string, gauge) and compare results.

• Experiment with hybrids: combine spin mains with comfort crosses.

• Pre-stretch poly strings to reduce initial tension drop.

  
  

🧾 UNI‑CORD® Tennis String Comparison Table

Model	Type	Gauge	Stiffness	Power	Spin	Tension Loss	Comfort
THE UNIVERSAL 1.35	Multifilament	1.35	4/10	7/10	4/10	3/10	9/10
THE PUNCHER 1.30	Polyester	1.30	7/10	7/10	6/10	6/10	5/10
THE EXPLOSIVE 1.30	Polyester	1.30	6/10	8/10	6/10	6/10	6/10
THE KILLER V2 1.20	Polyester	1.20	6/10	8/10	9/10	7/10	5/10
THE POWERFUL V2 1.24	Polyester	1.24	7/10	7/10	7/10	6/10	5/10
THE STRONGER V2 1.25	Polyester	1.25	7/10	6/10	8/10	7/10	5/10
THE TOUCH PLAYER V2 1.25	Polyester soft	1.25	5/10	7/10	5/10	5/10	8/10
THE SPINNER V2 1.25	Polyester	1.25	6/10	7/10	10/10	7/10	5/10
THE STRIKER V2 1.24	Polyester	1.24	7/10	7/10	7/10	6/10	5/10
THE CLASSICER V2 1.30	Polyester	1.30	8/10	5/10	5/10	6/10	4/10
THE BLOCKER V3 1.30	Polyester	1.30	9/10	4/10	4/10	5/10	4/10
THE GUT V2 1.31	Natural gut	1.31	4/10	9/10	6/10	2/10	10/10

🔑 How to read this table

• Stiffness: Higher = more control, less comfort.

• Power: Energy return at impact.

• Spin: String’s ability to generate topspin.

• Tension Loss: How quickly the string loses its tension.

• Comfort: Arm-friendliness and reduced vibration.

🎯 How to use this comparison

• Arm-sensitive players: THE UNIVERSAL 1.35 or THE TOUCH PLAYER V2 1.25

• Spin and power seekers: THE SPINNER V2 1.25 or THE KILLER V2 1.20

• Control-oriented competitors: THE BLOCKER V3 1.30 or THE CLASSICER V2 1.30

• Hybrid lovers: Mains THE SPINNER V2 + Crosses THE UNIVERSAL

• All-rounders: THE STRIKER V2 1.24 or THE POWERFUL V2 1.24

  
  

Conclusion

Stringing is not guesswork—it’s physics. By understanding stiffness, gauge, tension, and energy return, you can rationally choose the perfect setup.

🎾 UNI‑CORD® and TennXpert provide the tools, knowledge, and professional stringing network to help you play your best—scientifically.