Terragor PBO Braided-Spoke Usage Guide
Version: V2.0 (fully revised edition)
Prepared by: WowBlue Culture & Technology Co., Ltd.
Brand: Terragor PBO Spokes
Foreword
Thank you for choosing Terragor PBO braided spokes.
This usage guide is an operational reference compiled from our in-house laboratory measured data (including ultimate tensile tests, 48-hour tension-holding tests, and factory inspection standards). It is intended to help you make the most of the performance advantages of PBO spokes and to avoid problems caused by improper handling.
If you have any questions during wheel building, please feel free to contact our technical support team.
1. Length Conversion
1.1 General Spoke Length Formula
PBO spoke length is calculated with the standard spoke-length formula, with the addition of our proprietary end-fitting geometry correction.
Standard formula:
L = √(A² + B² + C²) − S − H
where:
| Parameter | Meaning |
|---|---|
| A = R − r₂·cos(θ) | Rim radius − flange radius·cos(lacing angle) |
| B = r₁ − r₂·sin(θ) | Drive/non-drive side flange offset distance |
| C = r·sin(π·N_spokes/N_total) | Perpendicular projection of the flange hole to the hub center |
| S | Length occupied by the metal end fitting of the spoke (PBO-specific) |
| H | Nipple height |
The value of S depends on the metal end-fitting design; for the standard 266 mm specification, S ≈ 3 mm.
1.2 PBO Length Correction
Our PBO spokes are fitted with metal end fittings at both ends, so the effective length (fiber-section length) does not equal the total length. In addition, PBO braided fiber undergoes an initial take-up phase on first tensioning (the braided structure progressively tightens from a relaxed state to a stable state), so the nominal length must compensate for this effect. Factory tolerances are as follows:
| Item | Value |
|---|---|
| Diameter tolerance | ±0.03 mm |
| Length tolerance | ±0.2 mm |
| Standard specification | 266 mm (total length, including both metal end fittings) |
| Thread specification | M2.3 × 0.45 |
Replacing steel spokes with PBO spokes:
PBO order length = steel spoke length - 2mm
Note: The PBO fiber braided structure undergoes an initial take-up phase on first tensioning; the nominal length is 2 mm shorter than a steel spoke to compensate for this effect. When building the wheel, simply tension progressively through the normal procedure — no additional steps are required.
Recommended procedure:
- Use a standard spoke-length calculator (such as the DT Swiss Spoke Calculator or Sapim Spoke Calc), entering your ERD, hub parameters, and lacing pattern
- We manufacture and deliver to the confirmed length, so you can build the wheel directly upon receipt
- If you need to trim the length yourself, the length must remain within the ±0.2 mm tolerance
1.3 Tension Conversion
IMPORTANT: PBO spokes must not be judged with tension-meter readings calibrated for steel spokes. You must convert readings using the dedicated cross-reference tables we provide.
We provide two tension-meter cross-reference tables:
- Table 1: tension-meter readings expressed as deflection values in mm (range approx. 0.59–2.10 mm)
- Table 2 (universal model): tension-meter readings expressed as unitless scale values (range approx. 10.5–24)
⚠️ Always read from the PBO column of the cross-reference table — never substitute the steel column; otherwise the deviation can exceed 50% and may cause the wheel build to fail.
Recommended static wheel-building tension (derived from the calculations in Whitepaper V2.0):
For a baseline configuration of 1:1 symmetric lacing and a small flange with a PCD of 40 mm, a rear drive-side static tension of 140–160 kgf is recommended.
This range is drawn from Chapter 4 (power-domain analysis) and Chapter 7 (core conclusions) of the PBO Braided-Spoke Wheelset Technical Whitepaper V2.0. This tension covers riding power of 200–800 W, with peaks remaining below the 300 kgf safety limit.
2. Compatible Hubs and Rims
2.1 Hub Compatibility
PBO spokes are a brittle material (zero ductility) and cannot disperse stress concentrations through micro-yielding. Hub selection is therefore the most important decision before wheel building — a wrong choice cannot be compensated for by wheel-building technique.
We strongly recommend small-flange hubs (PCD 38–42 mm)
Small flanges keep the bending moment within a safe range:
| Parameter | Recommended value | Reason |
|---|---|---|
| Drive-side flange PCD | 38–42 mm | Reduces bending moment by 37%; the aluminum-alloy hub enters the infinite-life regime |
| Non-drive-side flange PCD | Standard or slightly smaller | Carries no drive torque; allows further weight reduction |
| Flange root thickness t | ≥6 mm | Ensures flange-root strength and prevents fatigue cracking |
Tests show that the bending moment generated by a large flange cannot be dispersed by PBO's rigidity, and fatigue cracks develop at the spoke holes of the aluminum-alloy hub flange.
FMI (flange bending-moment index) comparison:
| Flange type | PCD | Relative FMI |
|---|---|---|
| Small flange | 40 mm | 0.63× |
| Large flange | 64 mm | 1.0× |
2.2 Lacing Compatibility
A 2:1 (asymmetric) lacing pattern is not recommended; a 1:1 symmetric pattern is preferred, as it delivers more balanced performance and more reliable long-term stability. With a 2:1 pattern, stability is slightly worse under ultra-high-power seated efforts and the non-drive side carries a higher risk of slackening. If spoke count must be reduced because of wheelset structural constraints, be sure to assess whether the rim strength can withstand an asymmetric tension distribution.
A 1:1 symmetric lacing pattern is strongly preferred:
- The non-drive and drive sides are loaded evenly, and both sides always work together
- Immunity to cascading failure — even if 2–3 spokes slacken slightly, the remaining spokes stay tensioned
- No one-sided torsional vibration; superior overall stability
2.3 Rim Compatibility
| Rim type | Compatibility | Notes |
|---|---|---|
| Carbon clincher rim | ✅ | Ensure the ERD matches the spoke length |
| Carbon tubular rim | ✅ | Same as above |
| Aluminum rim | ✅ | Same as above |
| Offset rim | ⚠️ Use with caution | Left/right spoke lengths must be recalculated |
Rim matching requirements:
- The spoke-hole diameter must match the threaded end (M2.3) and the nipple size
- Nipples of brass or aluminum alloy, specification M2.3 × 0.45, are recommended
- We recommend measuring the rim ERD rather than relying on the nominal value, to ensure tension uniformity
3. Wheel-Building Instructions
3.1 Receiving Inspection
After receiving the product, inspect each spoke individually:
| Inspection item | Standard | Tool |
|---|---|---|
| Appearance | Metal end fittings free of contamination, paint loss, scratches, and deformation | Visual |
| PTFE protective layer | Even surface, no cracking, no wrinkling, firmly adhered to the shaft without gaps | Visual |
| Length | ±0.2 mm | Steel ruler (on a flat surface) |
| Diameter | ±0.03 mm | Caliper (measure at multiple points at both ends) |
| Thread | Clean, even, free of burrs | Visual + trial fitting with a nipple |
If any item fails, please take photos for the record and contact our after-sales team within 7 days of receipt.
3.2 Tension Cross-Reference Tables
Measure tension with the tension-meter cross-reference tables we provide.
Measured PBO spoke tension data (from the in-house laboratory):
| Load (kgf) | Tension-meter reading ① (mm) | Deflection ① (mm) | Tension-meter reading ② (universal model) | Deflection ② (mm) |
|---|---|---|---|---|
| 60 | 0.82 | 0.85 | 11.5 | 0.87 |
| 70 | 0.95 | 0.96 | 14 | 0.97 |
| 80 | 1.10 | 1.07 | 16 | 1.09 |
| 90 | 1.20 | 1.17 | 17 | 1.19 |
| 100 | 1.31 | 1.28 | 18 | 1.33 |
| 110 | 1.45 | 1.39 | 19 | 1.44 |
| 120 | 1.54 | 1.50 | 20 | 1.54 |
| 130 | 1.63 | 1.62 | 21 | 1.62 |
| 140 | 1.74 | 1.73 | 22 | 1.73 |
| 150 | 1.84 | 1.83 | 22 | 1.85 |
| 160 | 1.93 | 1.93 | 23 | 1.95 |
| 170 | 2.01 | 2.05 | 23 | 2.06 |
| 180 | 2.10 | 2.15 | 24 | 2.19 |
Note: Tension meter ① is a deflection-type meter (readings in mm); tension meter ② is a universal model with unitless scale readings. The specific models of the two tension meters and the recommended wheel-building tension ranges are pending confirmation and will be supplemented later.
Cross-reference data for steel spokes:
| Load (kgf) | Tension-meter reading ① (mm) | Deflection ① (mm) | Tension-meter reading ② (universal model) | Deflection ② (mm) |
|---|---|---|---|---|
| 60 | 0.59 | 0.54 | 10.5 | 0.52 |
| 70 | 0.70 | 0.67 | 13 | 0.58 |
| 80 | 0.84 | 0.73 | 14 | 0.64 |
| 90 | 0.95 | 0.81 | 15 | 0.73 |
| 100 | 1.10 | 0.90 | 17 | 0.79 |
| 110 | 1.26 | 0.99 | 17.5 | 0.87 |
| 120 | 1.36 | 1.07 | 18 | 0.94 |
| 130 | 1.44 | 1.16 | 19 | 1.03 |
| 140 | 1.52 | 1.25 | 20 | 1.10 |
| 150 | 1.59 | 1.34 | 20.5 | 1.19 |
| 160 | 1.65 | 1.44 | 20.5 | 1.26 |
| 170 | 1.72 | 1.54 | 21 | 1.35 |
| 180 | 1.77 | 1.64 | 21.5 | 1.42 |
3.3 Wheel-Building Parameter Reference
Note: The following parameters are recommendations, not mandatory standards; wheel builders may adjust them based on experience.
| Parameter | Rear wheel | Front wheel |
|---|---|---|
| Flange PCD (mm) | 38–42 | 38–42 |
| Lacing | 1:1 symmetric | 1:1 symmetric |
| Nipple torque | 2.0–2.5 N·m | 2.0–2.5 N·m |
| Tension deviation control | ±5% | ±5% |
4. Stress Relief
4.1 Stress-Relaxation Characteristics
The following data come from the 48-hour tension-holding test in our in-house laboratory (document no. VW-QM-A0-003):
| Time phase | Stress decay rate | Cumulative decay |
|---|---|---|
| 0–1.25 h | Fast (1.70 kg/h) | 1.70 kg |
| 1.25–8 h | Fast → slow (falling to 0.15 kg/h) | Approx. 2.0 kg |
| 8–48 h | Extremely slow (0.05 kg/h at the end) | Total decay 0.46% |
| After 48 h | Approaches zero | — |
Total permanent creep: only 0.02 mm (virtually negligible)
4.2 Resting Relaxation Period (A Critical Step)
PBO spokes complete the great majority of their stress relaxation within the first 24 hours after wheel building. The resting relaxation period is the key to long-term wheelset stability and must not be skipped.
Tune the wheel to the target tension
↓
Rest for 24 hours (a full day)
↓
Fine-tune to the target tension
↓
Delivery
Points to note:
- Do not ride immediately after building. A 24-hour rest is the minimum requirement.
- Most relaxation is completed during the rest period, so no further re-tuning is needed after the final fine-tuning.
- The 0.02 mm permanent creep has a negligible effect on wheelset tension and requires no additional compensation.
- Every spoke undergoes a full inspection with a 180 kgf suspended load for ≥5 minutes before leaving the factory — but please note that this is not a wheel-building tension standard.
5. Notes on Use
5.1 Absolute Prohibitions
The following actions will cause product damage or personal-safety risks. Please observe strictly:
| Prohibition | Consequences |
|---|---|
| Pairing with large-flange hubs (PCD ≥45 mm) | Excessive bending moment → fatigue cracking of the hub flange |
| Judging readings directly from the steel-spoke column of a tension meter | Tension deviation of 50–100% → wheel-building failure |
| Bending the PBO spoke body | Irreversible fiber damage → fracture |
| Applying tension above 300 kgf | Rupture risk (measured ultimate limit 330–335 kgf) |
| Cutting or grinding the PBO braided fiber | Destroys the fiber structure → loss of strength |
| Mixing PBO spokes with carbon-fiber spokes | Damping characteristics differ greatly; uncoordinated wheelset response |
| Using a J-bend hub with straight-pull spokes | The end-fitting design is only compatible with straight-pull lacing |
| Using nipples other than the M2.3 × 0.45 specification | Thread mismatch → stripping |
| Using 180 kgf (the factory full-inspection standard) as the daily riding tension | 180 kgf is a safety inspection value, not a recommended riding tension |
5.2 Items Requiring Caution
| Item | Recommendation |
|---|---|
| Adopting a 2:1 (asymmetric) lacing pattern | Stability is slightly worse under ultra-high-power seated efforts and the non-drive side carries a higher risk of slackening; a 1:1 symmetric pattern is preferred. Rim strength must be assessed when reducing spoke count to the extreme |
| Trimming spoke length | Only the metal end fitting may be trimmed; cutting the braided fiber body is strictly prohibited. For length adjustments, we recommend returning the spokes for processing |
| Nipple torque | Use a torque wrench and keep it within 2.0–2.5 N·m; overtightening can strip the M2.3 threads |
| Front-wheel tension | Do not exceed 100 kgf. The front wheel carries no drive torque, and excessive tension instead reduces shock absorption |
| Batch matching | We recommend using spokes from the same production batch in the same wheelset, as end-fitting dimensions may vary slightly between batches |
| Salt-spray environments | The metal end fittings pass ≥96 h salt-spray testing, but regular inspections are still recommended for long-term coastal riding |
5.3 Daily-Use Notes
Slack check (before every ride)
Press the wheel laterally and check the non-drive-side spokes:
- Plucking produces a clear pitch → the spoke stays tensioned; condition is normal
- Plucking produces a dull or silent tone → the spoke has slackened and needs re-tensioning
In-season maintenance schedule
| Maintenance item | Interval | Notes |
|---|---|---|
| Check for loose nipples | Every 500 km | The braided body does not creep, but micro-movement at the end fittings needs monitoring |
| Tension uniformity check | Every 500 km | Calibrate using the tension-meter cross-reference tables we provide |
| Visual inspection | Before every ride | Check the metal end fittings, braided surface, and PTFE protective layer for anomalies |
UV protection
The molecular backbone of PBO fiber contains benzobisoxazole ring structures. When these structures absorb ultraviolet light (300–400 nm), they undergo photolytic chain scission, causing an irreversible loss of fiber strength. The core of PBO spoke protection is therefore photoprotection, not abrasion protection (see Section 5.6 of the PBO Braided-Spoke Wheelset Technical Whitepaper V2.0).
- The PTFE protective layer on the spoke surface is the critical protective structure and is fully opaque — never peel it off yourself
- Do not continue outdoor use once the PTFE protective layer is damaged and the fiber is exposed. If localized damage to the PTFE protective layer is found, replace that spoke immediately
- For long-term storage, keep spokes away from light in a dry, room-temperature environment, and avoid direct sunlight
6. Spoke Dimension Drawings
The following are the engineering drawings of the Terragor PBO braided spoke (with key dimensions labeled).
See the figure above for the overall spoke length, fiber-section length, metal end-fitting dimensions, thread specification (M2.3 × 0.45), and diameter tolerances.
(The drawings have been inserted into the Feishu document.)
(Drawings pending insertion.)
Contact Us
For technical inquiries or after-sales feedback, please contact our technical support team through your supplier channel.
Version: V2.0 (fully revised edition)
Date of compilation: 2026-07-02
Disclaimer: This guide is based on the in-house laboratory measured data and technical knowledge of WowBlue Culture & Technology Co., Ltd. We reserve the right to update the content as the product evolves. In the event of special circumstances during actual operation, please refer to our latest technical guidance.