Tru Pro Firewire Review: The Triangular Spin String and What Makes It Different
Share
Most shaped co-polys use four, five, six, or eight edges. Tru Pro Firewire uses three — a triangular profile that takes a different approach to spin generation. Fewer edges means each edge is sharper and the string itself is more structurally angular. The result is aggressive bite on ball contact, a string that Tru Pro claims has ranked number one in spin testing for three years running. This is a breakdown of what that claim means, how Firewire actually plays, and who it suits.
The Triangular Profile — Why Three Edges
The physics of a shaped poly spin string comes down to two things: edge grip and snapback. Edges dig into the ball briefly at contact, imparting rotation. The string then deflects and snaps back to position while the ball is still in contact, adding further rotation. More edges generally mean more grip surface; fewer, sharper edges mean more concentrated bite per contact point.
A triangular profile pushes this toward maximum bite per edge. The three edges of Firewire are sharper than the individual edges of a six or eight-sided string — the string deflects more dramatically at each contact point. This is why triangular profiles typically deliver more aggressive spin than hexagonal profiles at similar stiffness levels. The trade-off is feel: the concentrated edge contact produces a crisper, more pronounced sensation at ball impact than a rounder or softer profile.
Performance Characteristics
Firewire's USRSA stiffness is 236 — meaningfully softer than Solinco Hyper-G (290) and Babolat RPM Blast (273), which means the aggressive spin profile does not come with the arm punishment typical of the stiffest tour shaped polys. For a string designed around maximum bite, 236 is a reasonable stiffness level — it places Firewire in the medium-stiffness range despite the aggressive profile.
Tension maintenance is above average: Firewire recorded a tension loss of 14.18 lbs in USRSA testing — the best figure among the Tru Pro strings tested, better than Ghost Wire (16.27 lbs), Durafluxx (16.87 lbs), and comparable to Tour Status (14.66 lbs). Better tension maintenance means the string plays more consistently between restrings and does not go dead as quickly.
Control is the other defining characteristic. The triangular edges bite and redirect the ball rather than trampoline it back — Firewire is a low-power string. Players who generate their own pace and want to shape the ball aggressively will find it suits their game. Players who need the string bed to add power will find Firewire leaves them working harder.
Firewire vs Pure Rush — Which to Choose
Pure Rush (hexagonal) is the livelier, more arm-friendly, more accessible option. Firewire is the spin-specialist, the more aggressive, more control-oriented sibling. If you want maximum topspin from the Tru Pro lineup and your swing speed is fast enough to activate the triangular profile, Firewire is the call. If you want a balanced spin-power-comfort package, Pure Rush is easier to get along with.
The player most likely to prefer Firewire: a 4.5–5.5 baseliner with a heavy, fast swing who already uses a shaped poly and wants more spin bite without significantly more stiffness. The player most likely to prefer Pure Rush: anyone who wants spin and power in a more forgiving package, or who is new to shaped co-polys and does not yet know their preference.
Firewire Boost — The Pre-Built Hybrid
Tru Pro sells Firewire Boost as a pre-configured hybrid that pairs Firewire's spin profile with Ghost Wire as the cross string. The logic: Firewire mains provide aggressive spin bite, Ghost Wire crosses add comfort and reduce overall stiffness. Ghost Wire's USRSA stiffness of 188 offsets Firewire's 236 to produce an overall string bed that is noticeably softer than a full-bed Firewire setup. For players who want Firewire's spin but need to manage arm stress, Firewire Boost is the practical answer without buying two separate sets.
Who Should Use Firewire
Firewire suits aggressive baseliners at the 4.5 level and above who prioritise spin and control over power. Heavy swing speeds activate the triangular profile fully. If your swing speed is lower or you prefer a livelier, more elastic response at contact, the triangular profile will feel too precise and low-powered. In dense string patterns (18x20), Firewire becomes even more controlled — better suited to disciplined, directional ball-striking than to generating topspin through speed alone. In open patterns (16x19, 16x20), the combination of pattern movement and triangular edge bite produces the most spin.
Tension and Setup Notes
String Firewire at your standard poly tension or slightly below. The low-power characteristic means you do not need to drop tension significantly to get comfortable depth — the string does not add much power regardless of tension. A range of 50–55 lbs is typical. If you use Firewire Boost (Firewire mains + Ghost Wire crosses), treat the crosses at the same tension as the mains — Ghost Wire does not require separate tension adjustment.
Firewire single sets and the Firewire Boost hybrid are available at The Tennis Store with shipping across Australia and New Zealand.
Frequently Asked Questions — Tru Pro Firewire
What profile is Tru Pro Firewire?
Firewire is a triangular (three-sided) co-polyester — one of the few triangular profile strings on the market. The three sharp edges grip the ball aggressively on contact and snap back quickly, producing high spin generation. Fewer edges than hexagonal or octagonal profiles, but each edge is sharper and the contact bite is more concentrated.
How does Firewire compare to Pure Rush?
Pure Rush (hexagonal, six-sided) is livelier, more powerful, and more accessible — the easier string to get along with. Firewire (triangular, three-sided) is more spin-aggressive, lower in power, and more control-oriented. For most players, Pure Rush is the better starting point. Firewire suits players who specifically want maximum spin bite and can tolerate a low-power, precise response.
What is Firewire Boost?
Firewire Boost is Tru Pro's pre-configured hybrid: Firewire in the mains, Ghost Wire in the crosses. It delivers Firewire's triangular spin profile from the mains while Ghost Wire (USRSA stiffness 188) softens the overall string bed significantly. The result is more spin than a full-bed soft poly with less arm impact than full-bed Firewire. One set covers the full restring.
What is the stiffness of Tru Pro Firewire?
Firewire 16g has a USRSA stiffness rating of 236 — softer than Solinco Hyper-G (290) and Babolat RPM Blast (273). For a spin-focused shaped poly, this is a reasonable stiffness level that makes Firewire more arm-friendly than many tour polys with a similar spin profile.
What tension should I string Tru Pro Firewire at?
String at your standard poly tension or slightly below — Firewire is a low-power string so there is no need to drop tension significantly for depth. A range of 50–55 lbs suits most players. If using Firewire Boost (hybrid), string mains and crosses at the same tension.
Is Tru Pro Firewire good for arm-sensitive players?
Better than most spin-focused shaped polys, but not an arm-friendly string by multifilament or gut standards. Its stiffness of 236 is below RPM Blast (273) and Hyper-G (290), which is meaningful. For arm-sensitive players who need spin, Firewire Boost (with Ghost Wire crosses) is the better choice than full-bed Firewire — the Ghost Wire cross drops the overall string bed stiffness noticeably.