Saucony Endorphin Speed 4 vs Adidas Boston 12 — Speed Trainer Showdown
Speed trainers sit between daily cushioned trainers and carbon-plated race shoes. They are fast enough for tempo work and long intervals, cushioned enough for moderate easy days, and durable enough to be your primary training shoe. The Saucony Endorphin Speed 4 and the Adidas Boston 12 are two of the best speed trainers available in 2025 — and they take meaningfully different approaches.
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At a glance
| Endorphin Speed 4 | Boston 12 | |
|---|---|---|
| Weight | 218g | 228g |
| Heel drop | 8mm | 6mm |
| Heel stack | 35mm | 35mm |
| Forefoot stack | 27mm | 29mm |
| Midsole hardness (HC) | 25 | 26 |
| Energy return | 74% | 72% |
| Toebox width | 94mm | 92mm |
| Plate | Nylon SpeedRoll | Lightstrike Pro |
| MSRP | $160 | $140 |
| CoreScore | 90 | 88 |
Midsole and plate
The biggest technical difference is the foam compound. The Endorphin Speed 4 uses PWRRUN PB — a PEBA-based foam — paired with a nylon SpeedRoll plate. The Boston 12 uses Lightstrike Pro (also PEBA-based) with a Dreamstrike+ EVA layer underneath for durability.
Both are fast. But the PWRRUN PB in the Speed 4 is marginally softer (HC 25 vs 26) and the energy return is slightly higher (74% vs 72%). In practice this means the Speed 4 has a more cushioned, bouncy feel at easy paces, while the Boston 12 feels crisper and more direct.
The plate geometry differs significantly. Saucony's SpeedRoll nylon plate has a dramatic rocker curvature that naturally promotes forward momentum — some runners love this; others find it pushy. Adidas's plate in the Boston 12 is less aggressive, sitting as a stiffer base rather than an active rocker. The Boston feels more neutral; the Speed 4 feels more propulsive.
Weight and size
The Speed 4 at 218g is 10g lighter than the Boston 12. Over a marathon, this difference is marginal. In a 12×800m session, you will not notice it. What you will notice is the Endorphin Speed 4's rocker geometry — it shortens ground contact time and makes faster turnover feel less effortful.
The Boston 12 fits narrower: 92mm toebox vs 94mm on the Speed 4. The Speed 4 also comes in B (narrow) width, D (standard), and 2E (wide). The Boston comes in D only. If you have wider feet, the Speed 4 is the only option here.
Which type of runner suits each shoe
Endorphin Speed 4 suits:
- Runners who want the super shoe feel at a lower price point
- Wide-to-regular forefoot (3 widths available)
- Anyone who responds well to rocker geometry
- Training runs from 10K to half marathon effort
- Runners who want one shoe from tempo through long runs
Boston 12 suits:
- Runners who prefer a flatter, less rocker-forward feel
- Narrower feet
- Runners who like a slightly firmer, more precise platform
- Half marathon to marathon pace work
- Runners transitioning from Adidas Ultraboost who want more performance
Durability
Both shoes use PEBA foam which degrades faster than EVA — expect 400–600km before noticeable midsole compression. The Boston 12's Dreamstrike+ underlayer adds structural durability and the Continental rubber outsole coverage (patches at heel and forefoot) is excellent. The Endorphin Speed 4's XT-900 rubber is good but covers less outsole area.
For pure mileage lifespan, the Boston 12 has a slight edge.
Price
The Boston 12 retails at $140 vs $160 for the Endorphin Speed 4. Both offer strong value in the speed trainer tier.
Our recommendation
Buy the Endorphin Speed 4 if: you have wide or regular-width feet, want more cushion and bounce at easy paces, or are drawn to the rocker-assisted geometry.
Buy the Boston 12 if: you have narrow feet, prefer a flatter platform, or want the slightly better durability story of the Continental outsole.
Both are excellent shoes. The Speed 4 edges ahead on cushioning and width versatility; the Boston 12 on outsole durability and precise feel. Either will make your track sessions and tempo runs better than any standard daily trainer.