Nike ZoomX Invincible Run Flyknit 2 review

Who should buy the Nike ZoomX Invincible Run Flyknit 2

We hold the opinion that the Invincible Run Flyknit 2 should be a part of your running shoe rotation if you're looking for a: 

• running shoe that's comfy for recovery to easy days 
• fun shoe for short runs 
• protective and stable shoe for long miles (up to a marathon distance). 

Who should NOT buy it

If there's one thing we can all agree about the ZoomX Invincible Run Flyknit 2, it's crazy expensive. So, if you want to save money, we highly recommend sticking to the older version—Nike ZoomX Invincible Run. Since there's a newer iteration, it's going to go on sale for a much lower price. And hey, they're not that far off. 

Durability is also an issue for this trainer. For a solid, tank-like alternative, it's best to go for the Nike Pegasus 38. Ultimate traction even on wet roads? Go for its big brother—the Nike Pegasus 39.

Nike Invincible Run FK 2 vs. 1

The second version of the Nike Invincible Run Flyknit didn't change that much. So, those who loved the first version are going to be stoked that it doesn't go through a complete overhaul. 

Here are the small changes applied to this edition: 

• For stable transitions, it has a wider base.
• To max out protection, this version has more foam than the last. 
• The laces have been updated with a much thinner design to ramp up lockdown. 
• To keep weight at a minimum, the padding around the collar has been trimmed down. 

Not exactly for hot weather

We believe that this Nike shoe is much better suited for cool weather. This is because of the tightly woven knit upper paired with a padded tongue.

With the smoke test, we can see how poor the ventilation is. On a 1-5 scale where 5 is the most breathable, this shoe received 2. Therefore we can confirm that it's not the airiest shoe.

Nike ZoomX Invincible Run Flyknit 2 (left); Adidas Runfalcon (right). 

We use a smoke-pumping machine and cover up the shoe mouth entirely so that the smoke is only able to escape through the upper. 

In addition to the smoke test, we always check how transparent the upper is. In the case of the Invincible 2, not much light passes through the fabric, proving its below-average breathability.

As part of our lab tests, we took some pictures of the knit upper with a microscope.

Knit uppers are usually great when it comes to comfort, but they are not the best in class for breathability. That's exactly what happens with the Invincible Run 2. 

In the two photos, we can clearly see the difference between a mesh upper, which comes with large holes for ventilation, and a knit upper, which has a much denser texture.

A home for the sole

The shoe's jumbo-thick ZoomX sole made us fall in love with its plushness! We felt as though we were sinking into the cushioning. It is an exceptionally comfortable shoe. 

Even just walking around in it is a treat. So if you're coming back from an injury, the Invincible Run Flyknit 2 is a no-brainer. 

Using a durometer to check the foam, we discovered that the Nike ZoomX Invincible Run Flyknit 2 is indeed extremely soft. It's a whopping 117% softer than the average and is among the plushest shoes on the market.

The Nike Invincible Run Flyknit 2 will make you glide

Its rocker geometry is a solid A+. It made transitions feel velvety smooth in this Nike shoe. We could feel the rocker geometry just by walking in it.

It may not be as pronounced as in some other shoes (take the exaggeratedly rockered New Balance Fuelcell SuperComp Trainer, for instance) but it does its job excellently.

Nike ZoomX Invincible Run Flyknit 2 (top) vs. New Balance Fuelcell SuperComp Trainer (bottom).

Not your regular daily runner

In addition to being plush, the Invincible FK 2 is also very springy and lively. It has some nice feedback to it. 

We found it to be a fun, trampoline-like ride.

No achy feet

Apart from the comfort it offers, this Nike shoe also has great shock-absorbing qualities. This super cushy running shoe was made for maximum impact protection. It mutes out the harshness, keeping the hips, knees, and ankles safe.

Using a caliper, we measured the shoe's heel stack at 35.5 mm, slightly different from the marketed 37 mm, yet still taller than average (33.2 mm).

Contrary to the official figure, we found that at the forefoot the midsole is not 28 mm high, but 23.5 mm! This also means that the heel-to-toe drop is 12 mm and not 9 mm as officially stated.

The insole of the Invincible Run FK 2 is 3.3 mm, while the average is 4.5 mm. There was probably no need to use a thicker insole in this case, as the shoe already offers plenty of soft cushioning underfoot. 

Ready for the sharp corners

There are plastic rails in the heel that keep the foot locked in position. We really appreciated this feature when our legs started to get tired. On top of this, it has a wide base that ensures steady strides.

The sole at the forefoot is slightly wider than most shoes we tested. We measured 116.9 mm, which is 4 mm wider than average. 

This, together with the TPU heel clip, can help with stabilizing the foot.

Room for big toes

Version one of the Nike Invincible Run already had a wide toebox. And in this iteration, it's made (slightly) wider. It has a good amount of room for those with fat toes and even those with wide feet. And if you're clocking up the miles, don't worry about foot swelling; you have more than enough space here.

We double-checked this in the lab and found that the widest part of the upper is indeed 3 mm wider than the average.

Great even in cold weather

As mentioned before, this is a soft shoe. What's more, it's also flexible: in our test, it scored 2 out of 5 (where 5 is the stiffest) both for longitudinal and torsional flexibility.

The second test confirms the results we found in the first one: out of all the shoes we had in our lab, it's 35% more flexible. 

What's astonishing, is that it does not change much when the temperatures go down. When we put it in a freezer, we found that it became 27.2% less flexible, well below the average of 44%, and its foam got only 21.8% firmer (the average is almost 27%).

Visible at night? Try again Nike

The shoe has a reflective insert positioned on the external side of the toe box, but it's just too tiny to be of real help when it's dark. Besides, the shoe would be much more visible if it had one more reflective detail on the back.

Outsole is underwhelming

Yes, it grips on light trails, but for $180 traction is not enough to make up for its lack of durability.

The results we had in our lab might explain the poor durability of the outsole. Soft outsoles tend to last less than hard ones, and the rubber here is 9.2% softer than average.

And worse, it's not even the grippiest on wet concrete. The tiny nubs didn't do much to prevent us from slipping a bit.