How sports shoes and sneakers are made
Most sports shoes and sneakers use strobel construction. The upper is closed into a sock by stitching a flexible strobel board to its bottom edge, so there is no stiff insole board. The sock is pulled onto a last and then cemented to a sole unit, which is usually a midsole of EVA foam or PU with a rubber outsole glued or moulded to it.
The cementing is a chain of steps, and each one can go wrong:
- The upper is marked with a bite line where the sole will meet it, then roughed along the bonding area.
- Primer is applied to the upper and the sole. EVA soles often need a UV-activated primer or a chemical wash.
- Adhesive is applied to both surfaces, dried, and heat-reactivated in a tunnel.
- The two are pressed together, then chilled to set the bond before the last is removed.
Lifestyle sneakers with a cupsole, a moulded rubber tray, are often stitched through the side wall as well as cemented. Exports of leather-upper sports footwear (HS 64031920) were US$296.64 million and textile-upper sports footwear (HS 640411) US$71.93 million in FY2025-26 (Department of Commerce, TradeStat, provisional).
What we check on sports shoes and sneakers
| Check | How it is checked | What fails |
|---|---|---|
| Sole bond | Sole edge pressed at toe, flex zone and heel; shoe flexed sharply at the ball; factory peel tester supervised where available | Gaps along the edge, toe or heel opening, adhesive not wetted |
| Bite line and glue overflow | Line where upper meets sole examined all round | Bite line marks showing, cement on the upper or foxing, uneven sole wall |
| Midsole and outsole | Midsole checked for creases, compression marks, paint chips; outsole pattern and colour | Cracked or creased foam, uneven paint, wrong outsole colour |
| White soles and colour migration | White parts checked in a light box against the sample for yellowing and staining next to coloured uppers | Yellowed soles, dye from the upper bleeding into white foam |
| Eyelets and laces | Eyelets pulled and checked for sharp edges; laces checked for length and aglets | Eyelets loose or tearing, wrong lace length, missing aglets |
| Insole and collar | Sock liner removed and refitted; collar padding and heel counter compared left to right | Sock liner too short or creased, lumpy collar, crooked heel |
| Logo and trims | Logo position, print and embroidery against the artwork on both shoes; reflective trims | Logo misplaced or misprinted, trims peeling |
| Size and labels | Size label inside the tongue against the box; material label | Size mismatch; wrong or missing material label |
Common sports shoe and sneaker defects and how they are classed
| Defect | Typical cause | Class |
|---|---|---|
| Broken needle or metal fragment in the shoe | No needle control in stitching | Critical |
| Sole opening at the toe or heel | Missed priming, wrong reactivation temperature, short press | Major |
| Yellowed white midsole or outsole | Oxidation of rubber or foam, light, heat, wrong packing paper | Major |
| Colour stain from upper into white parts | Unfixed dyes migrating in heat and humidity | Major |
| Visible cement overflow | Too much adhesive above the bite line | Major or minor, by size |
| Logo in a different position on left and right | Misaligned print or embroidery jig | Major |
| Bite line pencil marks visible | Marks not cleaned | Minor |
| Loose thread ends | Poor trimming | Minor |
PU midsoles can also break down by hydrolysis after long storage in humid conditions. This cannot be seen at a pre-shipment inspection; ask for a hydrolysis test from a lab if the shoes will be stored for a long time. Your defect list decides the final class.
Market rules for sports shoes
- Material label (EU and UK). A mesh upper is textile, a synthetic leather upper is "other materials", and a rubber or EVA sole is "other materials", under Directive 94/11/EC and the UK's 1995 regulations. Coated leather has its own pictogram where the coating is thicker than the limit set in the directive.
- PAHs (EU). REACH Annex XVII entry 50 limits eight PAHs to 1 mg/kg each in rubber or plastic parts in direct and prolonged or repeated skin contact, and 0.5 mg/kg in articles for children. Rubber collars, insoles and some outsoles made with carbon black or extender oils are where this shows up. See REACH.
- Phthalates and DMFu (EU). Entry 51 limits DEHP, DBP, BBP and DIBP to 0.1% in plasticised material, which matters for PVC prints and trims. Entry 61 bans dimethylfumarate.
- Prop 65 (California). DEHP in PVC parts and lead in metal eyelets can require warnings. See Prop 65.
- Children's sizes (US). Sneakers for children 12 and under need lead content compliance, third-party testing, tracking labels and a Children's Product Certificate. See CPSIA.
Packing, transit and your purchase order
White soles yellow faster in heat and light, and some packing papers make it worse. Many buyers specify acid-free or anti-yellowing tissue and avoid sealing shoes in clear plastic in the sun. Mesh uppers crush under a shoe placed on top, so pairs are boxed heel to toe with paper stuffing. A container in summer can reach temperatures that soften adhesives, so a weak bond found at inspection is likely to open in transit.
Put these in your purchase order:
- Upper, midsole and outsole materials and colours, with the approved sample pair.
- Bond requirement: peel strength figure if you need one, and the test method.
- Whiteness reference for white soles and the packing paper to be used.
- Logo artwork, position and method (print, embroidery, emboss, heat transfer).
- Lace length per size, eyelet type, insole specification.
- Size chart and size run per carton; material label and origin marking.
- Restricted-substance list and lab tests for PAHs and phthalates.
For canvas sneakers with vulcanised soles, see canvas and textile shoes; for other sports goods, see sporting goods inspection. Book an inspection anywhere in India.
Sources
- Department of Commerce, TradeStat: commodity-wise exports (HS 64031920, 640411; FY2025-26 provisional)
- Directive 94/11/EC on the labelling of materials used in footwear (EUR-Lex)
- Commission Regulation (EU) No 1272/2013, REACH Annex XVII entry 50 PAHs (EUR-Lex)
- Commission Regulation (EU) 2018/2005, REACH Annex XVII entry 51 phthalates (EUR-Lex)
- ECHA: Substances restricted under REACH (Annex XVII)
- CPSC: Children's Product Certificate