Top-10 Shoe Defects Every Buyer Should Know

Everyone can appreciate the value of a good shoe. In order to retain and keep your customers happy, it’s important to maintain good quality standards for your products. The most efficient way to do that is to recognize the most common defects and proactively address them to avoid disruptions in your supply chain. To that end, we’ll share with you the top 10 defects that V-Trust inspectors always look out for in shoes during a pre-shipment or during-production inspection.

 1. Opened seam

An open seam anywhere on the shoe constitutes either a critical defect in baby products, or a major defect in other products. It can seriously affect the product function and structural integrity.

Causes:

1. The wrong thread was used, or the thread did not have enough strength to support the tension during sewing
2. Faulty sewing process, such as the under thread is missing or too loose, so it lacks the support for the top seam.

 2. Broken stitches

Broken stitches are a major defect in every product, no matter where it is located on the product itself, as it can compromise the structural integrity.

Causes:

1. The thread was accidentally cut or burned when trimming the seam in the checking process
2. Burned and weakened or broken on the machine during production

3. Poor or weak cementing (outsole, others)

Poor or weak cementing, like broken stitching, can cause problems with integrity, but may be a minor defect if the gap is smaller than 2 mm between the sole and shoe body. In other places on the shoe, it can be classified as a minor defect if the deformity is smaller than 5 mm.

Causes:

1. Insufficient glue was used during bonding
2. Not enough pressure on outsole when gluing

4. Asymmetric quarter height

Asymmetric quarter height is when the height of the rear of one shoe does not match the other. This is considered a minor defect if the difference is less than 2 mm, but major if it exceeds this measurement. Such a visible cosmetic deviation can make your product look low quality to your customers.

Causes

This is a fault during the lasting process. The allowance of the upper is not consistent on the back during counter lasting.

5. Yellow transformation

Yellow transformation is discoloration of one or both of the shoe soles, usually with a yellowish hue. This is a major defect if it is worse than 4 grey scales’ difference when compared to the original specification.

Causes:

Light colored or transparent material or TPU will turn yellow as it ages and oxidizes when exposed to air. This can be a sign of older material being used for production. Newer material should be used for this type of production.

6. Puckering/wrinkles

Puckering and wrinkles, especially in leather shoes, may be either a minor defect with less than 1 cm of wrinkling on the rear or bottom of the shoe, or major if found on any other visible area.

Causes

1. Not smoothed out during the lasting process
2. Natural wrinkles or bar present in genuine leather which were not caught prior to production.

7. Slanted heel

A slanted heel of any deviation from a 90⁰ angle to the floor is considered a major defect for either one or both of the shoes. Not only is this a cosmetic problem, but could become a safety concern if the slant is large enough on heels that are very high. Extreme slanting could cause sprained ankles, so this must be inspected consistently

Causes:

A fault during heel assembly. The heel impacts the screw between the insole and heel, and/or the screw or heel is slanted.

8. Sole not flat

When the sole is not flat, the defect is minor if the gap between the sole bottom and the floor is less than 5 mm. Any larger, and it becomes a major defect. Large gaps are unpleasant for aesthetics, and may cause irregularities in the walking experience of the wearer.

Causes:

1. Poor shape of outsole
2. The outsole is deformed during the heating process.
3. For vulcanized shoes, it is a common defect. If the gap is less than 3mm and feels fine while wearing, it is accepted.

9. Detached rivet

A detached rivet is always considered at least a major defect, no matter the location, and is a critical defect if it may detach within a 36-month timeframe for baby shoes. During a pre-shipment inspection, this is measured with a pull-gauge. 90 N of force is applied for 10 seconds. Detachment represents a failure to last through 36 months. This is a big concern for not only structural integrity, but could be a choking hazard for children as well.

Causes:

1. If adhesive is used to secure rivets or other accessories, there may not be enough glue or the glue is too weak.
2. If pressed together to secure the rivets, the pressure was too weak or uneven.

10. Peeling leather, tears, and other damage

Peeling leather or other surface damage is a major defect if the damaged section is located on the top, front, or sides. It is minor if it is on the back or bottom AND less than 2 mm in size. This is an obviously unattractive fault in craftsmanship, and will detract from your company’s quality image.

Causes:

1. The upper was scratched on some sharp point on a production machine, such as during the rubbing process before outsole gluing or the lasting process
2. The material is too old, so the coating is peeling off

Often, the main causes of shoe defects are due to either poor equipment maintenance or subpar material and production practices. While not every defect is avoidable, they can absolutely be mitigated with standardized procedures and proper maintenance of production machines, as well as professional product quality control. Attention to these details can help you retain customers and minimize your losses on defects and returns. 

The factory should set up a production maintenance schedule and follow it in order to prevent machinery failures and future product defects. Thus, when seeking a factory to produce your shoes, we advise conducting a factory audit to ensure the production line equipment is in use and is regularly maintained.

You, as the buyer, may want to add these defects to your own inspection requirements or tech pack to refine your supply chain management. For insight on how to compile your own inspection list or tech pack, check out QC tips | How to set a product’s Quality level for your supplier and Building a Tech Pack for Garment Production and Quality Control.

V-Trust can help to conduct a product inspection and factory audit of your shoe supplier in China, India, Vietnam, Bangladesh, Thailand, and Malaysia. Our full-time inspectors and auditors will help to spot the non-conformities of your shoes to ensure the quality of your goods, and ultimately, your reputation.

For more information concerning quality control, please feel free to contact us at info@v-trust.com.