ASICS S4 Plus Review: A Purpose-Built 4-Hour Marathon Shoe That Never Left Japan

Introduction

Most marathon shoes are built for the front of the pack. The ASICS S4 Plus takes the opposite approach: it is a purpose-built shoe for runners targeting a four-hour marathon, designed around comfort, stability, and smoothness over pure speed. The catch is that ASICS only sells it in the Japanese market, so it has become one of those import-only releases that runners trade and hunt down through resale communities.

Getting your hands on one outside Japan takes effort, so the real question is whether it earns that effort. After lacing it up for a ten-mile cold-weather run, the short answer is that it is a genuinely good shoe with a distinct personality: calmer and more comfortable than a typical race day racer, but lighter and peppier than a max-cushion trainer.

Who This Product Is For

This shoe makes the most sense for runners who spend three to four hours on their feet in a marathon and prioritize comfort above all else. It suits heel strikers especially well, since ASICS added full rubber coverage around the heel specifically because most longer-distance marathoners land there. It is also a strong long-run shoe for higher-mileage runners who want something smoother and lighter than a bulky trainer without committing to an aggressive elite racer.

If you are chasing personal bests in the three-hour range, this is not your shoe. There are faster, more explosive options in the ASICS lineup and beyond. But for the target audience, the design choices make sense.

How It Is Built

The S4 Plus uses a dual-foam construction: a layer of firmer race foam on top with a thicker, denser training foam underneath. The layout is conceptually similar to the Adidas Boston 12, though the S4 Plus puts race foam along the entire length of the midsole rather than just a puck in the forefoot. There is a plate inside, and the geometry scoops down at the forefoot in a way that resembles the MetaSpeed Edge Paris.

Stack height measures right around 40mm in the heel, and the weight comes in at roughly 260g in the tested size. That puts it lighter than the SuperBlast 2 and heavier than dedicated race shoes like the MetaSpeed Edge Paris, which lands around 193g.

Main Strengths

The first standout is grip. On wet, snow-dusted roads the traction was excellent, right up there with the best rubber in the category. For a shoe meant to carry you through three-plus hours in any conditions, that confidence matters more than almost anything else.

The second is smooth comfort. The ride is not soft or squishy, but it glides. The four-foot rocker is one of the best in recent memory, noticeably smoother than the SuperBlast 2 or Magic Speed 4, and the shoe disappears on foot within the first mile. The heel was the biggest pre-run concern given its narrow 75mm base, but the firmer bottom foam provides enough structure that there was no wobble at all, even on pace pickups.

Third is versatility. Despite being built for long, relaxed efforts, it feels peppy when you push the pace. It has less bite than the MetaSpeed shoes, but a powerful midfoot landing activates the race foam and rolls you forward in a way that feels surprisingly lively for a comfort-first marathon shoe.

Things to Consider Before Buying

The main trade-off is character. This is a calm, mellow shoe. It does not have the explosive pop of the MetaSpeed Sky Paris or the bouncy energy return of the Cloudboom Strike, and the denser bottom foam dampens some of the forefoot snap. If fun is what you want from a racer, look elsewhere.

It also does not feel especially robust at faster paces. The foams compress a fair amount in the forefoot and have a lighter, airier quality rather than the indestructible feel of the Boston 12. A wider base and taller stack would have addressed this, and the 75mm heel width remains a puzzling choice for a shoe whose whole job is stability.

Sizing is another quirk of the import route: it fits more like the SuperBlast than the snug race fit of the MetaSpeed shoes, so going true to size is the safer call.

How It Compares to the Rest of the Lineup

Within ASICS’s own range, none of the widely available alternatives do exactly what the S4 Plus does. The Magic Speed 4 is faster and lighter at around 255g, but the S4 Plus feels more planted and more comfortable in the heel, making it the better long-run pick. The GlideRide Max is softer and better for recovery days, but it sinks in more, while the S4 Plus rolls instead. The SuperBlast 2 is the closest spirit, but it feels heavier to get moving and can feel choppy by comparison; this is one of the smoothest shoes ASICS has made.

Outside the brand, the closest construction match is the Hoka Mach X2, which uses the same firm-over-soft dual-foam layout with an even more aggressive rocker. The Salomon S/Lab Spectur was an earlier attempt at the same four-hour-marathon concept with a wrapped carbon heel, though it found little traction with American runners. The New Balance SC Elite v4, Hoka Cielo X1, and On Cloudboom Strike all offer lower-weight race day alternatives, with the Cloudboom Strike in particular delivering more pop at 224g, at the cost of a narrower, softer platform.

Buying Advice

If you live in Japan and want a dedicated long-run or four-hour-marathon shoe, this is an easy recommendation. Outside Japan, your realistic options are the Magic Speed 4, GlideRide Max, or SuperBlast 2. For most people wanting the closest experience, the GlideRide Max captures roughly the same comfort-first idea in a softer package, while the Magic Speed 4 covers the speed end.

For runners who can find the S4 Plus through import channels and resellers, it slots beautifully into a rotation as the long-run shoe: light enough to feel streamlined, stable enough to trust when tired, and grippy enough for bad weather. Durability should also be solid given the generous rubber coverage front and rear.

Conclusion

The ASICS S4 Plus is a thoughtful shoe built for a runner ASICS rarely designs for: the one out there for four hours. It trades aggression for smoothness, grip, and comfort, and on its own terms it succeeds. The narrow heel and muted personality keep it from being a universal pick, but as a long-run cruiser with genuine race shoe DNA, it is one of the most comfortable options in the brand’s entire lineup. If it ever reaches a wider market, it would deserve a spot on the shelf.