What spoke hole strength measures
The spoke hole is a concentrated stress point in the carbon rim spoke bed. When a spoke is tensioned during wheel building, it pulls against the rim at the hole. Spoke hole strength is the rim’s resistance to that pull force at this specific zone.
This is a localized structural property, not a measure of overall rim stiffness or weight. A rim can be very light and still have strong spoke holes, or the reverse. The strength of the spoke hole zone depends on the layup design, local fiber reinforcement, and how the hole is finished after molding.
What is a spoke-hole pull-through test for carbon rims?
The pull-through test isolates the spoke hole zone directly. A small section of the rim — typically spanning three spoke holes — is cut from the rim and clamped securely. A spoke and nipple are installed in the center hole, and a hydraulic press or universal testing machine applies increasing load along the spoke axis, pulling the spoke away from the rim.
The test records either the force at which the hole fails or confirms that the hole holds above a specified threshold without cracking, deforming, or allowing the spoke to pull through.
This is a rim-level test performed on a cut sample. It applies a static load at a single hole, in a single direction.
What does kgf mean in a carbon rim spoke-hole strength test?
Force in spoke hole tests is typically reported in kilogram-force (kgf) or newtons (N). Both units measure the same thing; kgf is more common in factory test reports and supplier datasheets.
A value such as “350 kgf” is incomplete without its endpoint. It may mean the sample held to a specified pass threshold, first showed a crack at that load, or reached pull-through failure at that load. A useful report also identifies the sample, fixture, spoke and nipple interface, loading direction, and acceptance criteria.
What is the difference between spoke tension and spoke-hole strength?
These two figures are related but measure different things.
Spoke tension is the working load a spoke carries in a built and tensioned wheel. It is not one universal number: the approved target depends on the rim, hub, spoke, nipple, lacing pattern, wheel side, and build method. Park Tool’s wheel-tension guidance likewise advises following the rim manufacturer’s current specification.
Spoke-hole validation load is a localized static test result at the nipple-seat zone. If the stated value is a pass threshold, it shows only that the tested sample met that threshold under the recorded method. A first-crack or pull-through failure result is a different endpoint.
Do not calculate a wheel-system safety factor by simply dividing a single-hole test load by working spoke tension. The cut-sample fixture does not reproduce load sharing around a complete wheel, and a static pull test does not by itself establish impact or fatigue performance. Those questions require separate project-level validation.
At DeerCycles
Where required by an approved project method, DeerCycles can perform spoke-hole strength validation up to 350 kgf at the nipple-seat zone. The force level and result apply to the identified sample and method; they are not a blanket rating for every rim model or order.
The project record should distinguish among no cracking up to the target load, first observed cracking, and pull-through failure. Sample identity, fixture, spoke and nipple interface, loading direction, target load, endpoint, and acceptance criteria should be agreed during sample approval.
External technical reference
Park Tool’s wheel-tension guidance explains that acceptable spoke tension is generally governed by the rim and should follow the rim manufacturer’s current specification. See the Wheel Tension App instructions and spoke-tension measurement guide.