Asics S4 review

8 expert score
8 user's score
As editorial policy, we do not accept free samples. We purchased this pair at Asics Japan with our own money.
Review written on 28th March by Brandon Law Marathon Runner and Shoe Expert
160 other reviews

Asics S4 Verdict

The ASICS S4 is a carbon racer designed specifically for the runner who is targeting a sub-4 hour time for the full marathon. It shares many characteristics with the Magic Speed series but the S4 uses FF Turbo in its midsole which makes it feel more energetic. The S4 has a comfortable ride which is on the firm side and an outsole which is highly durable so it can be used for training runs as well as racing.

The pros

  • Great value
  • Durable outsole
  • Comfortable upper
  • Aggressive carbon plate

The cons

  • Narrow midfoot
  • Not widely available

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Rating breakdown

Build quality
Sole unit
Value / Price

Facts / Specs

8.5 oz (241 g)

34 mm.
28 mm.
Heel drop
6 mm.
Carbon plate
Full length carbon plate


Buy half size bigger
Heel fit
Midfoot fit
Toebox fit

Cushioning & ride

Type of cushioning
Amount of cushioning
Highly cushioned
Very stable


Daily training
Long distance racing
Ultra distance racing

Who should buy the Asics S4 ?

If you’re looking for an affordable speed trainer or racer and you find the Magic Speed too firm for you, the S4 is a good choice. It has a stiff carbon plate and mild forefoot rocker which provides snappy transitions.

Who should not buy the Asics S4 ?

If you enjoy a soft, flexible ride, the S4 is not for you. If you’re an experienced runner looking for the fastest super shoe, the S4 is also not for you.

Asics S4 Introduction

Picture of ASICS S4

When I ran my first marathon, my target was sub 4 hours. I wasn’t sure what shoe to go with but I chose the Reebok Floatride Run Fast because it was light, energetic and comfortable.

I finished with a time of 4:38 but that was due to my training and not the shoe choice.

If you’re a mid-pack runner and you’re looking to run your first marathon, you need a shoe which is well-cushioned, stable, comfortable and energy-saving.

Today, most of the carbon-plated racers on the market are designed for the elite runner, a runner capable of breaking world records. These runners have excellent form and efficiency so their racing shoes don’t need to have much stability or comfort. These racing shoes are also not designed to be durable because most elite runners get multiple free shoes from the brands.

ASICS has now come up with a unique racing shoe, a racer designed for runners looking to run under 4 hours for a full marathon. According to an article on the ASICS website, for a man, anything under 4 hours could be considered a good marathon time, putting you in the top 43% of runners.

S4 stands for speed, stability, safety and sub-4. The S4 looks similar to their flagship marathon racers, the Metaspeed Sky+ and Edge+ but there are a few big differences. The S4 has a dual-density midsole, a wider base and more outsole rubber.

The S4 weighs 240 g (8.5 oz) for a men’s US9 which is the exact same weight as the Magic Speed 2. This is a bit disappointing considering the S4 has FF Blast Turbo (ASICS’ premier racing foam) in its midsole while the Magic Speed 2 doesn’t. It costs about 150 USD but currently, it’s only available for purchase in Japan.

Asics S4 First Impressions

Picture of ASICS S4

My first run was a speed workout of 10 x 500 m. It felt a bit stiff and firm on that first run but over time, it softened up and became a bit more flexible. It feels way different after 50 km compared to straight out of the box.

The shoe felt firmer than I expected it to. It felt stable and snappy but not as lively as the Metaspeed Sky+. The forefoot rocker also wasn’t as pronounced as the Sky+.

It took a bit more effort to increase my speed and cadence than a top of the range super shoe but the workout was enjoyable. The firm toe-offs allowed me to increase my pace easily and transitions felt very smooth.

The shoe that it reminded me of most was the Magic Speed 2 but the S4 felt more energetic. It was easier to pick up the pace in the S4. It felt like a hybrid of the Magic Speed 2 and the Metaspeed Edge.

Asics S4 Upper

Picture of ASICS S4

The S4’s upper looks like it was lifted straight off the Metaspeed series, and that’ a good thing. It’s light, breathable and very comfortable. Overall foot lockdown is excellent and the laces feel like premium racing laces.

The thin tongue is not gusseted and it does slide down during runs but it doesn’t bother me because the laces don’t cut into the top of my feet.

Just like the Magic Speed 2, the S4 fits a half size small so I went up a half size and the fit is perfect. It has a narrow midfoot so if you have flat arches, you might feel some pressure on your arches.

Asics S4 Sole Unit

Picture of ASICS S4

An average pace of 5:40 per km (9:07 per mile) is required to run a sub 4 hour marathon so for the long run test, I deliberately ran at that exact pace for 32 kilometres. While the ride wasn’t very engaging or exciting, I found that that pace is the sweet spot for the S4. The mild forefoot rocker helps the S4 feel energy-saving over long distances.

The midsole is the exact setup that I wanted in the Magic Speed series: FF Turbo on the top, Flytefoam at the bottom. The Magic Speed series doesn’t have FF Turbo, which is the premier ASICS midsole foam that they use in the Metaspeed series so the S4 is slightly softer.

I find the ride of the S4 to still be on the firm side so if you like really plush, squishy rides, this shoe isn’t for you. I would have liked it to have been around 20% softer. The energy return isn’t as high as something like the Superblast but there’s more ground feel in the S4.

Picture of ASICS S4

Apart from long-distance racing, the S4 is good for tempo and steady runs, and decent at interval workouts. For easy and long runs, I prefer something softer with more squish.

The S4 has a full-length carbon plate which is more flexible than the ones in the flagship racing series. It makes the shoe a bit more stable and makes the forefoot feel more snappy but it doesn’t give you a springboard type of forward propulsion.

The outsole’s durability is impressive. There’s thick, durable rubber on all the high wear areas and the exposed Flytefoam midsole doesn’t show much wear either. This is a racer that can double up as a trainer because of how durable it is.

Asics S4 Conclusions

Picture of ASICS S4

If I was running my first marathon again, I would definitely race in the S4. It has an affordable price, it’s stable and is very capable of holding a 5:40 pace for 4 hours.

Right now, my marathon target is closer to the 3 hour mark so I wouldn’t race in the S4 because it doesn’t offer as much speed assistance as the Metaspeed Sky+ or other flagship super shoes.

If you’ve raced in any of the top of the range super shoes before, then you’ll be a bit disappointed racing in the S4 because its ride isn’t as fast or as fun but if it’s your first carbon-plated racer, you’ll be more than happy with it.

I think the S4 is a great idea because not all runners can afford top of the range super shoes. Slower runners don’t need as much propulsion and they value stability/comfort in a racer more. The S4 ticks all those boxes.

You could race in an ASICS speed trainer like the Noosa 15 or the Evoride Speed but they are carbon plateless so they don’t give you that carbon-loaded race day feel when you lace them up.

The closest shoe to the S4 is the Magic Speed 2 (I haven’t run in the Magic Speed 3).

The S4 is slightly cheaper but you have to order it from Japan which might work out to be more in the end. The S4 is more lively than the Magic Speed 2 due to its FF Turbo and it offers slightly more speed assistance.

Hopefully ASICS brings the S4 to more regions in the future.

How does the S4 compare?

Asics Magic Speed 3
Asics S4
Saucony Endorphin Speed 3
Expert score
User score
Best price
Retail price
7.8 oz
8.5 oz
8.10 oz
Heel Drop
7 mm
6 mm
8 mm
Recommended for
Racing, speedwork, long distance racing
Racing, speedwork
Racing, speedwork, daily training
Cushioning type
Cushioning amount
Medium cushioning
Highly cushioned
Highly cushioned
some stability
very stable
some stability
true to size
buy half size bigger
true to size

Why you can trust us

As editorial policy, we do not accept free samples from companies.
We purchased this pair of Asics at Asics Japan  with our own money.

This page contains affiliate links. As an Amazon Associate we earn from qualifying purchases. Read more about our policy.
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Asics S4 price comparison

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Reviewed by Brandon

This review was written by Brandon Law on 28th March.
Brandon is a South African who lives and trains in Malaysia. He is a marathon runner who eats, sleeps and dreams running shoes. While most people wear shoes to run, he runs to wear shoes.

User feedback (3)

  • avatar-comment-1034847
    4 months ago
    8 score

    How would you compare the S4 to the Evoride Speed? If you had only these two, which one would you choose for a marathon and a half marathon?

  • avatar-comment-1033770
    6 months ago

    Thanks for the review. I’m really on the fence about getting the S4 or the Superblast, currently I use the NB3 which I love but keen to try a new shoe for a full marathon next year. Other than the carbon plate, what’s the big difference between the two? Do both hold up for the full 42km? I currently run 4:15, really want that sub-4! Thanks, love you shoe reviews!

    • avatar-comment-1033800
      Brandon Law
      6 months ago

      Hi Simon. The S4 is firmer than the Superblast and more rigid. The Superblast has a lot more cushioning due to its thick stack height. I think the Superblast is the better option for you- it’s like a faster, lighter version of the NB3.

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Where to buy

Best offers today in United States, all prices in USD
Sorry - Product not found. Please try RunningWarehouse.Com to check in their assortment.
This page contains affiliate links Read more

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