Overview
EN ISO 17707:2005 - Footwear: Test methods for outsoles - Flex resistance (ISO 17707:2005) is a CEN-adopted ISO method for determining the flex resistance of shoe outsoles. The standard measures how sole materials and surface patterns influence cut growth and crack initiation under repeated bending. It applies to outsoles with a maximum longitudinal rigidity of 30 N (measured at 45° flex).
Key topics and technical requirements
- Scope: Method for assessing cut propagation and crack initiation on outsoles with longitudinal rigidity ≤ 30 N.
- Rigidity test: Outsoles are bent to 45° at (100 ± 10) mm/min and the force (0–50 N sensor, ±1 %) is recorded. Outsoles requiring >30 N at 45° are excluded from flex resistance testing.
- Flex resistance apparatus:
- Mandrel diameter: 30 ± 0.1 mm around which the outsole is flexed.
- Flexing rate: device capable of 135–150 cycles/min, flexing through 90° ± 2° about the mandrel axis.
- Cycle counter and firm end clamps to align the flexing line.
- Test pieces & conditioning:
- Test pieces may be taken from complete footwear or outsole units; attach a standard insole (cellulose board) of 2 ± 0.1 mm thickness and apparent bulk density 0.55 ± 0.05 g/cm³.
- Condition samples 24 h according to EN 12222 (standard atmospheres).
- Cut initiation and measurement:
- A single incision is made with a specified chisel; chisel is lubricated with soap and water.
- Initial cut length L(o) measured in fully flexed position (accuracy 0.1 mm).
- Subject outsole to 30 000 flexes; re-measure cut length L(f). Report cut growth as L(f) − L(o).
- Record additional cracks (number and longest length to 0.5 mm).
- Test report must include results, sample identification, test method reference, test date and any deviations.
Applications and users
- Useful for: footwear manufacturers, material suppliers, test laboratories, R&D teams, quality control and compliance engineers.
- Practical uses:
- Compare outsole compounds and tread patterns for durability against cut growth.
- Evaluate new outsole formulations or cleat designs during product development.
- Provide repeatable, standardised data for marketing claims and regulatory compliance for footwear performance.
Related standards
- EN ISO 20344:2004 - Personal protective equipment: Test methods for footwear (method basis).
- EN 12222 - Standard atmospheres for conditioning and testing of footwear.
- EN ISO 534 - Paper and board thickness/density (for insole specification).
Keywords: footwear test methods, flex resistance, outsoles, ISO 17707, cut growth, outsole rigidity, flexing test, footwear durability.