A01 · Applications
Rubber where it wears, foam where it lands.
An athletic sole is two jobs in one part. The ground gets abrasion resistance and the foot gets cushioning, and the programme succeeds or fails on whether the bond between them survives the flex test.
What this segment demands
Athletic soles are the one segment where the brief pulls in two directions at once. Cushioning wants low density and a soft compound; wear life wants the opposite. Resolving that with a single material means accepting a compromise on one of them, which is why almost every running and training sole ships as two densities — a rubber wear layer under the forefoot and heel, a foamed midsole carrying the rest.
That makes the bond, not the compound, the thing that decides the programme. A combination sole has a physical interface between two materials that flex at different rates, several hundred thousand times over the life of the shoe. Outsole-to-midsole peel strength is the test that catches a bad one, and it is the test worth writing into the specification before tooling is cut rather than after the first wear trial comes back.
The alternative is a one-piece moulded sole, where outsole and midsole are formed as a single part with no bond line to fail. It costs a degree of tuning — you cannot independently choose the two densities the way a bonded construction lets you — and it removes the failure mode entirely. Which of the two is right is a question about the shoe, not about the factory, and it is worth settling at the DFM review.
Which sole system, and why
More than one family will do the job. What separates them for this segment is below; the full specification envelope for each is on its own page.
The default for the segment. A vulcanised rubber outsole bonded to a foamed midsole gives you both densities and lets you place the rubber only where the tread actually wears, which is where the weight saving comes from.
Where the programme cannot carry a bond line — long service life, hard wear, or a market that returns shoes on delamination. Formed as one part, so there is nothing to peel.
For court, training and gym shoes where the midsole is built into the upper assembly rather than the sole, and the sole unit is a rubber outsole on its own.
Hardness we hold for this segment
Windows measured on the compounds we run, not the range the material category can reach. Rubber, foamed rubber and TPR are quoted in Shore A; EVA soles and midsoles in Shore C. Why the two do not convert.
| Application | Hardness | Density |
|---|---|---|
| EVA midsole, sport / running | 40–45 Shore C | 0.20 g/cm³ |
| Rubber outsole, casual / lifestyle | 60–65 Shore A | 1.15 g/cm³ |
What gates the specification
The tests that decide whether a sole for this segment passes. Eight rigs run on site; the full rig-to-standard mapping and what goes to an external laboratory is on the quality page.
| Outsole–midsole peel | The gate for any bonded construction. Specify it before tooling; a bond that fails at trial-shot stage is a tooling problem as often as a compound one. |
|---|---|
| Flex / cut growth | Ross flex to ISO 17707 or SATRA TM60. Sent to an accredited laboratory rather than run in house — the rig is not one of the eight on site. |
| Abrasion resistance | ISO 4649 method A on our DIN abrasion tester. The number a running brand cares about is loss under the forefoot strike zone, not an average across the sole. |
| Hardness | SATRA TM205. The EVA midsole is quoted in Shore C and the rubber outsole in Shore A; the two scales do not convert, and a spec sheet that mixes them is worth a second look. |
Where this stops being ours
- Performance-plate constructions — carbon or nylon plates encapsulated in the midsole — are a shoe assembly problem, not a sole moulding one. We mould the sole; the plate lamination sits with the shoe factory.
- Supercritical foamed midsoles in expanded TPU are a different process line from ours. If the brief names an e-TPU midsole, we are the wrong supplier for that layer and can still make the rubber outsole that goes under it.
- We do not run finished-shoe assembly. What ships is the sole unit.
What we need to quote this
Beyond the standard checklist: the strike-zone map if you have one, the target midsole density, and whether the construction is bonded or one-piece. If that last one is still open, send the shoe and we will come back with a recommendation and the reasoning.
The standard checklist, and the six stages a programme runs through, are on the development page.
Our own figures, not a category benchmark. Held across the six sole systems; a programme that moves them says so in the quotation. Full terms, tooling cost and mould ownership are on the OEM & ODM page.
Other footwear segments
Building for running & athletic?
Send the drawing, the sample or the standard you certify to. We come back with the sole system, a compound and hardness recommendation, and a tooling plan.