From materials science
to ride feel

A spoke is not a spring — it is a pre-tensioned string. PBO's stress wave travels 2.27× faster than in steel, energy retention is 95%, and the mean ultimate tensile strength is 332.5 kg — every figure comes from measurement.
This is not a material swap; it is a change in how force is delivered.

Read the whitepaper View measured data

332.5kg Mean ultimate tensile (measured)

2.27× Stress-wave speed · relative to steel

95% Energy retention

0.46% Total 48h tension decay

00

How a rigid molecular rod becomes strong and tough

The backbone of PBO (poly(p-phenylene benzobisoxazole)) is a rigid main chain of benzene rings alternating with benzobisoxazole rings — with almost no rotatable single bonds, the molecular chain is a nanoscale rebar by construction. Its strength and toughness are decided at the molecular level; what remains is to connect it to the wheel correctly.

PBO molecular structure: benzene and benzobisoxazole fused backbone (poly(p-phenylene benzobisoxazole)) — PBO molecular chain · benzobisoxazole repeat unit

01 · Rigidity

Coplanar, conjugated backbone

Benzene and oxazole rings are coplanar and conjugated; π-electron delocalisation raises bond energy and the segment cannot coil — rigidity is built into the structure.

02 · Orientation

Liquid-crystal spinning · highly oriented

During spinning the chains are fully extended and aligned along the axis in the liquid-crystal state, giving dense crystallinity and very few defects.

03 · Covalent

Load runs straight along the backbone

External force is carried by strong covalent bonds along the rigid backbone, with no flexible segment to buffer it — that is where the strength comes from.

01

A spoke is not a spring; it is a pre-tensioned string

A spoke's effective stiffness = pre-tension + material properties. PBO's density is only 1/5.1 that of steel, yet its stress wave is 2.27× as fast — for the same pedal stroke, steel spreads the force over time while PBO delivers it at once.

c Wave speed PBO ≈ 430 m/s

T₀ Pre-tension Wheel-building set value

ρₗ Linear density PBO = steel × 1/5.1

Wave-speed ratio c_PBO / c_steel = 2.27×

2.27×　relative to steel

Faster stress wave

About 430 m/s, so power reaches the ground sooner.

1/10　loss factor

Lower damping

Loss factor only 0.0001, about one tenth of steel.

95%　energy retained

Nearly lossless transfer

Pure fibre, no resin, no loss; carbon fibre retains only 5% of its energy because of the epoxy resin.

02

One spoke, two characters

At low tension the braided geometry is soft, absorbing and filtering vibration; at high tension the fibres straighten and stiffness approaches carbon fibre. Compliant at cruise, rigid at sprint — with no switch to flip.

25–45 GPa Braided-geometry zone

Low tension absorbs and filters vibration; the ride feels more planted.

280 GPa Fibre-bearing zone

High tension delivers stiffness directly, with no lag.

Close-up of PBO spoke braid texture and metal end — Product close-up · braid texture and metal end

Full data

03

From cruising to sprinting

The stress wave travels back and forth at 430 m/s — 1.3 ms one way. Derived for a rear-drive 140 kgf / non-drive 91 kgf (0.65 ratio), 1:1 symmetric, small-flange 40 mm PCD configuration.

Condition	Power	Drive-side peak	Notes
Cruise	200–400 W	155–175 kgf	Compliant and solid
Climb	600–800 W	195–235 kgf	Into the fibre-bearing zone
Critical	1000–1200 W	260–300 kgf	Non-drive side just goes slack; the margin stays clear
Limit	1400–1600 W	300–330 kgf	Below the 332.5 kg mean breaking load

04

Controlled specs and compatibility limits

Every dimension leaves the factory within controlled tolerance. When replacing a steel spoke, convert the length as L_PBO = L_steel − 2 mm.

Standard overall length: 266 mm (including metal end)
Length tolerance: ±0.2 mm
Diameter tolerance: ±0.03 mm
Thread spec: M2.3 × 0.45
Steel → PBO conversion: L_PBO = L_steel − 2 mm

HubSmall flange PCD 38–42 mm, flange root thickness ≥ 6 mm; large flanges with PCD ≥ 45 mm are strictly prohibited
Lacing1:1 symmetric; 2:1 is not recommended — high risk of non-drive-side slack
RimCarbon fibre, aluminium and tubular rims are all compatible; ERD must be measured to match
Offset rimUse with care; left and right spoke lengths must be recalculated

Full data

05

Wheel-building guide

The points below are taken from laboratory records. The complete guide also contains the tension reference table and wheel-building parameters.

a.

Tension reference

The PBO-specific tension table is mandatory; readout deviation must be ≤ 5%. Steel-spoke tables can deviate by more than 50% and must not be used.
b.

Static tension

Rear drive side 140–160 kgf, non-drive 91 kgf (0.65 ratio), deviation within ±5%, nipple torque 2.0–2.5 N·m.
c.

Rest

Leave the wheel to rest for 24 hours after building; most stress relaxation is complete, then fine-tune lateral runout, roundness and tension uniformity.
d.

Factory inspection

Every spoke is measured for appearance, length, diameter and thread; each record is archived with the batch.

06

Every spoke in the laboratory

Destructive tensile testing on a dual-column machine, 120 kgf held for 48 hours, 180 kgf full inspection and >300 kgf sampling — 12 factory inspection items recorded one by one. We break them so that every remaining one can be predicted.

332.5kg Mean ultimate tensile · 10–12% above target

2.37× / 4.15× Wheel-building tension / daily-riding safety factor

0.46% / 0.02 mm Total 48h tension decay / permanent creep

12items Factory inspection · full + sampling

Measured Terragor PBO braided-spoke wheelset — Measured product · carbon rim + PBO braided spokes

Full data

07

What you must not do

PBO's strength comes from highly oriented continuous chains. Any operation that breaks continuity makes the strength drop irreversibly — building it takes a whole production line, ruining it takes one action. The four rules below are hard constraints.

No large-flange hubs (PCD ≥ 45 mm)Bending moment exceeds the limit; hub flanges may fatigue-crack
Never read PBO tension with a steel-spoke tableDeviation can reach 50–100%; the dedicated table is required
Never bend or cut the braided fibreIrreversible fibre damage and loss of strength
Never exceed 300 kgf tensionMeasured breaking load is 330–335 kgf; keep the safety margin

UV protection: the PTFE layer is fully UV-opaque; factory UV ageing retains ≥ 90% strength, outdoor service life > 20 years. Never strip the protective layer.

Full data

08

Read the PBO spoke whitepaper

A complete record of the PBO braided-spoke development path: material selection, wave dynamics, geometry design, power-domain derivation and measured data. V2.1 · measured-data validation edition (V1.0 theoretical framework + VW-QM-A0-001/002/003 measured data).

Read the full whitepaper Review the measured data