Nike Ja Fly 4 review

We believe the Ja Fly 4 is a smart choice for:

• Track beginners performing short sprint trainings.
• Runners on a budget seeking an affordable and snug-fitting spike.
• Weekend warriors of the track and field world looking for a flexible Nike spike.

We do not recommend the Ja Fly 4 for distances beyond 400m. For those looking at longer races or training workouts, consider the versatile Nike Zoom Rival D 10.

We also believe that those seeking some cushioning and energy return will find the Ja Fly 4 lacking, as it is a direct-to-the-ground spike without any foam. For a more forgiving and responsive experience, we recommend upgrading to the Nike Air Zoom Maxfly, which features two Air Zoom units plus a substantial layer of bouncy ZoomX foam in the heel.

When we tested these spikes on the track, we discovered that the ride is remarkably close to the ground.

This finding aligned with our measurements when we clocked the heel stack of the Ja Fly 4 at a mere 11.2 mm.

We then measured the forefoot with our callipers and confirmed the same stack height as the heel.

As previously mentioned, the Ja Fly 4 contains no foam or rubber whatsoever.

As you might have guessed—no fancy math skills required this time—we found identical measurements in both the forefoot and heel, confirming this is a true 0.0-mm drop track spike. Get your Achilles tendons ready!

The insole of the Ja Fly 4, at 3.9 mm, is similar to those in Nike road running shoes and adds a crucial thin layer of cushioning underfoot.

Having just measured the midsole, we turned our attention to the upper. Given the narrow dimensions of the midsole, we anticipated a snug fit.

Indeed, with the toebox measuring just 81.9 mm, we can confirm that the Ja Fly 4 offers an ultra-tight, performance-oriented fit.

The toecap area features a pronounced taper, as our measurement at the big toe area was 69.2 mm.

Additionally, we found limited vertical space for toe movement in the upper. This design is ideal for those seeking a tight fit and for sprinting, but it may not suit anyone in need of a roomier spike.

The Ja Fly 4 features a classic 7-pin configuration in the forefoot, allowing for easy removal of the pins as needed.

Most spikes exhibit some torsional stiffness, but not the Ja Fly 4. We found it exceptionally flexible, easily bending and twisting without resistance, as it lacks plates, midsole and rubber. Consequently, we rated its rigidity at just 1/5.

The Ja Fly 4's heel counter is similar to those found in competition (road) running shoes, featuring minimal structure beyond a small cardboard piece and some padding. Consequently, our lab team rated its stiffness at just 2/5.

While all spikes tend to be narrower than road or trail shoes, the Ja Fly 4 is particularly small within the spike category, measuring just 88.0 mm across the forefoot. That's nearly as narrow as the width of your feet!

When we moved our callipers to the heel, we found an extremely narrow design, measuring just 55.1 mm.

However, it’s important to remember that this is a sprint spike, and landing on the heel is unlikely, so the narrowness is less critical.

Given its thick plastic outsole, we anticipated some stiffness, similar to the effect of Pebax-based plates.

Indeed, after our standardised 90-degree bend test, we registered 33.0N on our force gauge. This indicates a moderate level of stiffness, ideal for those seeking responsiveness without the extreme rigidity of a carbon plate.

Weighing just 5.1 oz (145g), this is among the lightest running spikes on the market!

The first thing we do in our lab with every shoe is to turn on the smoke-pumping machine and assess the shoe's breathability.

After testing the Ja Fly 4, we discovered it offers moderate breathability, which is acceptable for a track spike designed for short sprints. Ultimately, you won't be wearing it for extended periods, so the goal is to avoid poor ventilation. However, we believe Nike could enhance this aspect in the next version.

We also used a light to check for any variations in the thickness of the upper. We found that the shoe follows a traditional design—with a thicker heel for stability and thinner areas in the midsole and toebox.

Next, we examined the shoe under a microscope and noted that Nike used a very standard engineered mesh, without special technologies like Atomknit or Flyknit.

Considering the shoe retails for just £120, it's reasonable not to expect top-tier materials from Nike's lineup.

Finally, we took a close look at the upper. While there's nothing particularly fancy, we found more padding than expected, especially in the heel area, which earns a thumbs-up for comfort!

In our testing with a Dremel tool, the Ja Fly 4 proved quite resilient, earning a good score of 3/5.

This means that it possesses the necessary durability to handle the wear and tear expected for a track spike.

We then tested the heel padding of these spikes with our Dremel's spinning sandpaper tip—a crucial area as it often contacts the skin directly, making durability vital.

We are pleased to report an impressive score of 4/5. This result indicates fantastic durability in this critical area.

The Ja Fly boasts a 4.5 mm thick all-plastic outsole. This track spike contains neither rubber nor foam.

Despite its design focus on minimal weight, we were surprised to find the tongue measured at 4.1 mm thick. Although this is slender for an average road running shoe, it's on the comfortable side for a track shoe.

From our perspective, while the added thickness may seem minor, it highlights a deviation from the conventional ultra-light build expected in running spikes. 

Like its predecessor, the Ja Fly 4 omits a heel tab, which is anyway 100% unnecessary in a track sprint shoe.