Our verdict

We found the Ja Fly 4 from Nike to be an excellent spike for budget-conscious sprinters, offering strong performance alongside some premium features. In our lab tests, we noted that its upper is quite snug and could benefit from enhanced ventilation. Despite these minor drawbacks, it's a solid option for athletes seeking quality track spikes without breaking the bank.

Pros

  • Lightweight design
  • Removable pins
  • Cost-effective choice
  • Comfortable tongue
  • Enhances foot strength
  • Ideal for 60-200m sprints
  • Notched laces
  • Above-average durability

Cons

  • Limited breathability
  • No midsole
  • Extremely narrow upper

Audience verdict

83
Good!

Who should buy

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.

Nike Ja Fly 4

Who should NOT buy

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.

Nike Ja Fly 4 cutting

Breathability

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.

Nike Ja Fly 4 light

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.

Nike Ja Fly 4 mesh

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!

Test results
Ja Fly 4 3
Average 3.6
Compared to 9 track spikes
Number of shoes
1
Breathability
5

Durability

Toebox durability

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.

Nike Ja Fly 4 Toebox durability
Test results
Ja Fly 4 3
Average 2.9
Compared to 8 track spikes
Number of shoes
1
Toebox durability
5

Heel padding durability

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.

Nike Ja Fly 4 Heel padding durability
Test results
Ja Fly 4 4
Average 4
Compared to 8 track spikes
Number of shoes
1
Heel padding durability
5

Outsole thickness

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

Nike Ja Fly 4 Outsole thickness
Test results
Ja Fly 4 4.5 mm
Average 3.1 mm
Compared to 9 track spikes
Number of shoes
1.6 mm
Outsole thickness
6.4 mm

Cushioning

Heel stack

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.

Nike Ja Fly 4 Heel stack
Test results
Ja Fly 4 11.2 mm
Average 13.9 mm
Compared to 9 track spikes
Number of shoes
10.4 mm
Heel stack
19.8 mm

Forefoot stack

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

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

Nike Ja Fly 4 Forefoot stack
Test results
Ja Fly 4 11.2 mm
Average 13.2 mm
Compared to 9 track spikes
Number of shoes
8.6 mm
Forefoot stack
17.8 mm

Drop

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!

Nike Ja Fly 4 Drop
Test results
Ja Fly 4 0.0 mm
Average 0.7 mm
Compared to 9 track spikes
Number of shoes
-5.8 mm
Drop
4.1 mm

Insole thickness

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.

Nike Ja Fly 4 Insole thickness
Test results
Ja Fly 4 3.9 mm
Average 3.0 mm
Compared to 9 track spikes
Number of shoes
1.8 mm
Insole thickness
3.9 mm

Flexibility

Stiffness

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

Indeed, after our standardized 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.

Test results
Ja Fly 4 33.0N
Average 29.1N
We use an average of four tests. The video shows one of those tests.
Compared to 9 track spikes
Number of shoes
10.9N
Stiffness
66.6N

Stability

Torsional rigidity

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.

Test results
Ja Fly 4 1
Average 2.8
Compared to 9 track spikes
Number of shoes
1
Torsional rigidity
5

Heel counter stiffness

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.

Test results
Ja Fly 4 2
Average 1.7
Compared to 9 track spikes
Number of shoes
1
Heel counter stiffness
5

Midsole width in the forefoot

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!

Nike Ja Fly 4 Midsole width in the forefoot
Test results
Ja Fly 4 88.0 mm
Average 92.8 mm
Compared to 9 track spikes
Number of shoes
87.6 mm
Midsole width in the forefoot
99.6 mm

Midsole width in the heel

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

Nike Ja Fly 4 heel narrow

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.

Nike Ja Fly 4 Midsole width in the heel
Test results
Ja Fly 4 55.1 mm
Average 59.7 mm
Compared to 9 track spikes
Number of shoes
54.0 mm
Midsole width in the heel
67.9 mm

Size and fit

Toebox width at the widest part

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

Nike Ja Fly 4 upper

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

Nike Ja Fly 4 Toebox width at the widest part
Test results
Ja Fly 4 81.9 mm
Average 87.9 mm
Compared to 9 track spikes
Number of shoes
81.9 mm
Toebox width at the widest part
96.4 mm

Toebox width at the big toe

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.

Nike Ja Fly 4 Toebox width at the big toe
Test results
Ja Fly 4 69.2 mm
Average 73.1 mm
Compared to 8 track spikes
Number of shoes
68.3 mm
Toebox width at the big toe
77.1 mm

Removable pins

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

Nike Ja Fly 4 Removable pins

Comfort

Tongue padding

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.

Nike Ja Fly 4 notched laces

We were thrilled to discover premium notched laces, reminiscent of the Alphafly 3, in the Ja Fly 4. They really work wonders!

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

Nike Ja Fly 4 Tongue padding
Test results
Ja Fly 4 4.1 mm
Average 3.0 mm
Compared to 9 track spikes
Number of shoes
0.4 mm
Tongue padding
7.5 mm

Heel tab

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

Nike Ja Fly 4 Heel tab
Test results
Ja Fly 4 None

Weight

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

Nike Ja Fly 4 Weight
Test results
Ja Fly 4 5.11 oz (145g)
Average 5.57 oz (158g)
Compared to 9 track spikes
Number of shoes
4.59 oz (130g)
Weight
6.46 oz (183g)