Bally Flexometer Guide – EN ISO 20344 for Footwear

The EN ISO 20344 standard specifies test methods for personal protective footwear, including the Bally flexometer method to measure how footwear upper materials resist cracking and failure under repeated flexing cycles. In this test, rectangular test specimens are subjected to cyclic bending motion at fixed flexing angle and flexing speed. Damage such as surface cracking, finish chipping or crease failure is visually inspected at set cycle intervals.

Bally flex test results are reported as the number of flex cycles when first visible cracking or material failure appears. The EN ISO 20344 standard unifies multiple legacy regional  flex‑testing approaches for consistent lab‑to‑lab comparison for safety and protective footwear.

Flex resistance of footwear upper materials is important because it affects footwear durability, service life and visual appearance. In safety and work footwear, high flex‑resistance is required to resist crease cracking during repeated walking and bending movements.

While leather goods and coated synthetic uppers work on the controlled flex‑resistance principle. They have to withstand thousands of bending cycles without surface cracking. 

EN ISO 20344 is a globally recognized standard for protective footwear testing. It is widely accepted because it offers a standardized and reproducible testing method for the determination of flex‑resistance of footwear uppers, linings and coated textiles.

EN ISO 20344 is cross‑referenced in major international standards such as ISO 17694, SATRA TM 55, IULTCS/IUP 20‑1 and GB/T 20991. This cross‑reference proves the test recognition and credibility.

Description of How Bally Flexometer Test Equipment Works

The Bally shoe flexing tester determines how well flexible material resists crease‑cracking under repeated bending cycles. For testing:

1. The experimenter folds the test specimen in half, secures one end in the first clamp, turns the specimen inside‑out, and locks the free end into the second clamp which sits 90 degrees relative to first clamp. This clamping setup ensures correct specimen folding geometry without slippage.

2. After that, the movable clamp oscillates repeatedly at fixed angle and speed to flex the test specimen.

3. The instrument counts completed flex cycles; operators visually inspect the specimen at set cycle intervals and record the cycle number when first cracking or surface failure appears.

Modern Bally flexometer testers utilize digital cycle counters and multi‑station clamping fixtures. For example, the GT‑KC10A Bally Resistance Flexing Tester from GESTER complies with EN ISO 20344 and related international standards. It delivers reliable repeatable test results.

Use of Defined Flexing Angle, Flexing Speed and Sample Dimension

The EN ISO 20344 referenced Bally flex test is performed under set conditions. It helps to get comparable results across different laboratories.

1. A fixed flexing angle of 22.5° ± 0.5° is applied for specimen oscillation.

2. A fixed flexing speed of 100 ± 5 cycles per minute.

3. Standard specimen dimension: 70 ± 5 mm × 45 ± 5 mm.

These parameters ensure consistent test results across different labs. For example, if a full‑grain leather safety‑boot upper shows first cracking at 60 000 cycles under EN ISO 20344 conditions, the same material will give comparable results when tested globally following identical setup.

Measurement Output of Bally Flex Test (Cycles to First Crack)

The results of  Bally flexing tester test are reported as number of flex cycles achieved before first visible cracking or surface damage. Higher cycle values mean better flex‑crack resistance.

SATRA TM55 – Bally Flexometer for Footwear Upper Materials

SATRA TM55 is widely adopted across footwear manufacturing industry. This standard shares identical core Bally flexometer mechanical principle with EN ISO 20344, supporting both dry‑specimen and wet‑specimen testing.

ISO 17694 – Footwear Uppers & Linings Flex Resistance

ISO 17694 specifies flex‑resistance test for footwear uppers and linings, directly references Bally flexometer method and shares same specimen geometry and machine parameters as EN ISO 20344. Test outputs are comparable.

IULTCS/IUP 20‑1 – Leather Flexometer Method

IULTCS/IUP 20‑1 is classic international leather test standard for flex resistance of leather and leather finishes. It uses Bally flexometer principle, suitable for flexible leather materials below 3 mm thickness.

GB/T 20991 – Chinese Equivalent of EN ISO 20344

GB/T 20991 is Chinese standard for PPE footwear test methods. This standard is harmonized with EN ISO 20344, referencing identical Bally flexometer setup and parameters. Test results are fully comparable.

Pros and Cons of Each Method for Footwear‑Material Flex‑Resistance Analysis

EN ISO 20344 / GB/T 20991

These standards are best for global PPE footwear trade. Their results are comparable for safety‑footwear compliance testing.

SATRA TM55

It is mostly used within footwear manufacturing supply chain for material incoming QC. Fully compatible with Bally flexometer hardware.

IULTCS/IUP 20‑1

Optimized for pure‑leather material evaluation; widely used within tanneries for finished‑leather quality assessment.

ISO 17694

Covers both leather and non‑leather coated textile uppers for general footwear, not limited only to protective PPE footwear.

Safety & Occupational Footwear: Verifying Upper Material Durability

The safety footwear industry demands upper materials with reliable flex‑crack resistance. These materials withstand thousands of bending cycles during daily workplace usage. A high‑performance full‑grain leather safety‑boot upper achieving >100 000 dry flex cycles provides excellent crease‑crack resistance and long service life.

A low‑performance heavily finished synthetic upper failing at ~10 000 cycles delivers low‑cost appearance but poor long‑term durability.

Bally flexometer testing also supports cold‑climate footwear development. Sub‑zero temperature flex screening helps identify brittle coating formulations prone to winter‑use cracking.

Wet‑Condition Material Qualification for Outdoor & Work Footwear

Many work‑site footwear is exposed to rain and water splash. Wet‑specimen Bally flex test evaluates how uppers hold flex‑resistance after water contact. Some leather and coated fabrics show sharp drop in crack‑resistance under wet state.

Leather Goods & Accessories: Bags, Belts, Luggage Leathers

The performance of leather bags and luggage relies on good flex‑crack resistance for folding zones. High‑quality bag leather delivers high Bally flex cycles. Low‑grade finished leather may develop crease cracks after limited usage.