Our verdict

The Adidas Racer TR21 doesn't quite match the expectations set by its name. It isn't quite a racing shoe, but rather a hybrid between a comfortable everyday sneaker and a heavy running shoe. Affordable and flexible, this shoe is crafted with the beginner in mind, making it perfect for low-intensity jogs or walks in the park. However, we think if you're in the market for a genuine racing shoe or if you're a midfoot or forefoot striker, this may not be the ideal fit.

Pros

  • Functions well as a casual sneaker
  • Comfortable for all-day wear
  • Suitable for wide feet
  • Budget-friendly at only £80
  • Appealing aesthetic
  • Eco-friendly
  • Stable for heel strikers

Cons

  • Only for casual runs
  • Offers limited arch support
  • Insufficient forefoot cushioning

Audience verdict

87
Great!

Who should buy

We recommend the Adidas Racer TR21 for:

  • Heel strikers looking for a budget-friendly roomy shoe that aren't concerned about its heavier weight.
  • Individuals seeking a comfortable shoe for daily commuting, strolling around town, or walking the dog around the neighbourhood, in addition to one or two slow runs a week.
  • Runners specifically seeking environmentally-friendly running shoes.

Adidas Racer TR21

Who should NOT buy

If you're a forefoot or midfoot striker, you might want to look elsewhere—this shoe doesn't offer enough cushioning in those areas as it's designed for heel strikers. If you're in the market for an affordable running shoe suitable for those footstrikes, we recommend checking out the Saucony Axon 2.

Also, for serious runners looking to log heavy mileage or intense training, be aware: the Racer TR21 won't meet your needs.

It's clunky and lacks responsiveness, making it far from the ideal training partner. And despite its potentially misleading name, don't consider it if you're in the market for a dedicated racing shoe. For that purpose, we feel that the Adidas Adizero Adios Pro 3 is a better pick.

Adidas Racer TR21 parts

Breathability

While the TR21 isn't strictly a running shoe and you might expect breathability to be somewhat compromised, we found its performance to be okay. It doesn't measure up to top-tier shoes like the Saucony Triumph 20 in this aspect—the video speaks for itself—yet it's good enough to earn a standard 3/5.

The smoke-pumping test results were particularly surprising. When we held the upper to the light, it didn't appear breathable at all, seeming more akin to a 1/5 or 2/5 running shoe.

Our microscope examination provided the same impression. Besides capturing some stunning close-up images, it confirmed the TR21's knit upper as thicker than average.

Adidas Racer TR21 micro

Despite this, we must commend Adidas for their effort, even though this shoe falls below the average in our test results.

Adidas Racer TR21 microscope

Additionally, we should spotlight the upper's layered construction. This feature impresses as it boosts comfort, albeit at the expense of breathability. Keeping all these considerations in mind, scoring a 3 out of 5 here is indeed a great achievement.

Test results
Racer TR21 3
Average 3.8
Compared to 221 running shoes
Number of shoes
1
Breathability
5

Durability

Toebox durability

As we noted earlier, the TR21 is equipped with a knit upper. This comes with an advantage; knit typically elevates comfort. However, its downfall is a considerable lack of sturdiness, so we were ready for a disappointing outcome with threads flying everywhere.

Once we engaged the Dremel on the upper, spinning at 10K RPM, our fears were quickly confirmed. The TR21 was on a direct path to securing the lowest of scores: a 1/5.

Still, that's no justification. Other knit shoes, like the On Cloudswift 3, have truly excelled in this same test.

Adidas Racer TR21 Toebox durability
Test results
Racer TR21 1
Average 2.3
Compared to 155 running shoes
Number of shoes
1
Toebox durability
5

Heel padding durability

Regrettably, the tale is the same in the heel padding durability test with our Dremel.

The TR21 won a disappointing 1/5 for its lackluster durability. And it's not a brand thing—another Adidas shoe like the Ultraboost Light did much better.

Adidas Racer TR21 Heel padding durability
Test results
Racer TR21 1
Average 3.2
Compared to 151 running shoes
Number of shoes
1
Heel padding durability
5

Outsole hardness

Adidas played it safe with the outsole hardness on this model, with our measurement with the durometer showing it at 80.2 HC.

Adidas Racer TR21 Outsole hardness
Test results
Racer TR21 80.0 HC
Average 80.4 HC
We use an average of four tests. The photo shows one of those tests.
Compared to 272 running shoes
Number of shoes
54.9 HC
Outsole hardness
92.8 HC

Outsole durability

For our final test, we used the Dremel once again to evaluate the outsole's durability. Some Adidas shoes typically perform well in this aspect, thanks to their use of Continental rubber, but this shoe lacks that compound. As a result, it offers only average durability.

After removing the Dremel from the shoe, we noted a 1.24 mm indentation in the outsole.

Adidas Racer TR21 Outsole durability
Test results
Racer TR21 1.2 mm
Average 0.9 mm
Compared to 133 running shoes
Number of shoes
0.0 mm
Outsole wear
2.0 mm

Outsole thickness

Much like the average hardness, the thickness of the shoe is also pretty standard. After taking precise measurements, we determined that it stands at a mere 3.6 mm.

Adidas Racer TR21 Outsole thickness
Test results
Racer TR21 3.6 mm
Average 3.2 mm
Compared to 291 running shoes
Number of shoes
0.0 mm
Outsole thickness
6.6 mm

Weight

Who enjoys running around with brick-like shoes? We assume the answer is, not many!

That's why the TR21 weight of 11.20 oz (318g) doesn't seem all that appealing.

Adidas Racer TR21 Weight
Test results
Racer TR21 11.22 oz (318g)
Average 9.38 oz (266g)
Compared to 292 running shoes
Number of shoes
5.26 oz (149g)
Weight
12.56 oz (356g)

Cushioning

Heel stack

With its heel measuring 31.9 mm, the shoe packs enough Cloudfoam Super in this area to accommodate heel strikers.

Adidas Racer TR21 Heel stack
Test results
Racer TR21 31.9 mm
Average 33.6 mm
Compared to 291 running shoes
Number of shoes
7.6 mm
Heel stack
42.7 mm

Forefoot stack

The forefoot, however, falls really short. We measured it below 19 mm, which is extremely low by today's standards, and makes this running shoe a bad choice for any forefoot striker.

Adidas Racer TR21 Forefoot stack
Test results
Racer TR21 19.0 mm
Average 24.9 mm
Compared to 291 running shoes
Number of shoes
7.6 mm
Forefoot stack
35.8 mm

Drop

Adidas' official specifications give the shoe at a 34/26 mm stack for an 8-mm heel-to-toe drop. Yet, it's not uncommon for us to find discrepancies between the brand's stated measurements and our own.

With the Racer TR21, our meticulous measurements in the lab returned a 31.9/19 mm stack for a 12.9-mm heel-to-toe drop. That's almost a 5-mm difference from the numbers from Adidas. WOW.

Adidas Racer TR21 Drop
Test results
Racer TR21 12.9 mm
Average 8.7 mm
Compared to 291 running shoes
Number of shoes
-0.8 mm
Drop
16.1 mm

Insole thickness

The insole is somewhat thin at 3.4 mm, but it's not something we're overly concerned about. It wasn't a problem in any of our runs.

Adidas Racer TR21 Insole thickness
Test results
Racer TR21 3.4 mm
Average 4.5 mm
Compared to 287 running shoes
Number of shoes
1.5 mm
Insole thickness
7.3 mm

Midsole softness

Note: a low durometer measurement equals a soft material, whereas a high measurement means it's firm.

With a midsole softness measurement of 21.0 HA, the Racer TR21 delivers a well-balanced experience.

It's not excessively soft or squishy, and it's not too firm either. 

Adidas Racer TR21 Midsole softness
Test results
Racer TR21 21.0 HA
Average 21.4 HA
We use an average of four tests. The photo shows one of those tests.
Compared to 219 running shoes
Number of shoes
8.5 HA
Midsole softness (soft to firm)
41.5 HA

Midsole softness in cold

Note: a low durometer measurement equals a soft material, whereas a high measurement means it's firm.
Adidas Racer TR21 Midsole softness in cold

Difference in midsole softness in cold

We tested the shoe's performance under cold conditions by putting it in our freezer for 20 minutes.

Now, we can confirm that with a hardness of 28.3 HA, it's close to being considered firm, nearly reaching the 30 HA mark.

Given its £80 price tag, we expected this shoe's performance under cold temperatures to be subpar. This is typically the case with EVA-based midsoles.

So, the 34.5% increase in hardness didn't disappoint us too much. In fact, most shoes in this price range perform significantly worse.

Adidas Racer TR21 Midsole softness in cold
Test results
Racer TR21 34.5%
Average 25.6%
Compared to 218 running shoes
Number of shoes
0%
Difference in midsole softness in cold
100%

Stability

Lateral stability test

The moment we slipped our feet into the TR21, we immediately felt its impressive stability. What a pleasant surprise!

Torsional rigidity

The shoe appears and feels flexible, yet when it comes to torsional flexibility, it's fairly average, leaning more towards the firm side and we rated it at 3/5.

Test results
Racer TR21 3
Average 3.2
Compared to 270 running shoes
Number of shoes
1
Torsional rigidity
5

Heel counter stiffness

Adidas didn't took any risks designing the heel counter in the Racer TR21. It's not the usual super-soft heel because there's some resistance, primarily from a plastic piece that surrounds the area.

We rated it as a 2 out of 5, which in our view strikes a good balance between preventing heel slippage and maintaining comfort.

Test results
Racer TR21 2
Average 2.8
Compared to 254 running shoes
Number of shoes
1
Heel counter stiffness
5

Midsole width in the forefoot

The forefoot offers an average landing platform, measuring 113.9 mm. There's nothing out of the ordinary or negative to report here!

Adidas Racer TR21 Midsole width in the forefoot
Test results
Racer TR21 113.9 mm
Average 113.6 mm
Compared to 292 running shoes
Number of shoes
100.5 mm
Midsole width in the forefoot
126.5 mm

Midsole width in the heel

However, there's something interesting happening with the heel. We initially suspected that this shoe was designed with heel strikers in mind, given the large heel-to-toe drop and its very low forefoot stack.

This became even more evident when we measured the heel at 95.0 mm—wider than most shoes—which promotes stability for heel strikers.

Adidas Racer TR21 Midsole width in the heel
Test results
Racer TR21 95.0 mm
Average 90.5 mm
Compared to 292 running shoes
Number of shoes
74.9 mm
Midsole width in the heel
106.6 mm

Flexibility

Stiffness

We mentioned earlier that the shoe seemed flexible at first glance, but it didn't show that much when we tried to twist it. It's during the 90-degree bending test that the shoe truly astonished us with its flexibility.

We only made 13.7N of force to bend it to 90 degrees, so it ranks among the top 3% of the most flexible shoes we've ever analyzed in the lab.

Test results
Racer TR21 13.7N
Average 29.3N
We use an average of four tests. The video shows one of those tests.
Compared to 274 running shoes
Number of shoes
2.2N
Stiffness
94.4N

Difference in stiffness in cold

Under cold temperatures, the flexibility follows a similar pattern to the softness. The change is clearly noticeable.

Needing 21.9N of force to bend it to 90 degrees, it doesn't retain its super-flexible characteristic anymore.

This results in a 59.5% increase, which disappointingly underperforms compared to most other shoes.

Test results
Racer TR21 59.5%
Average 36.3%
Compared to 274 running shoes
Number of shoes
0%
Difference in stiffness in cold
148%

Size and fit

Internal length

At 272.9 mm, the shoe it's a little bit longer than it should (270 mm), but likely not enough to warrant sizing down unless your feet are particularly narrow.

Adidas Racer TR21 Internal length
Test results
Racer TR21 272.9 mm

Toebox width at the widest part

With a measurement of 100.4 mm, the Racer TR21 crosses the 100 mm threshold. This makes it, without a doubt, a wide shoe in the shelves.

Adidas Racer TR21 Toebox width at the widest part
Test results
Racer TR21 100.4 mm
Average 98.3 mm
Compared to 292 running shoes
Number of shoes
89.5 mm
Toebox width at the widest part
109.1 mm

Toebox width at the big toe

The area for the big toe follows suit, proving even wider in comparison to the rest of the shoe.

Adidas Racer TR21 Toebox width at the big toe

For those of us with wide feet, this shoe really fits the bill.

Adidas Racer TR21 Toebox width at the big toe
Test results
Racer TR21 79.5 mm
Average 78.0 mm
Compared to 166 running shoes
Number of shoes
60.4 mm
Toebox width at the big toe
92.5 mm

Tongue: gusset type

While we don't usually anticipate a gusseted tongue in a £80 shoe, it feels like a fantastic bonus when we do encounter one. Unfortunately, we're out of luck this time.

Adidas Racer TR21 Tongue: gusset type
Test results
Racer TR21 None

Comfort

Tongue padding

For a shoe tipping the scales at over 11 ounces, it's seriously disappointing to find just a 2.9-mm-thick tongue. This could lead to compromised comfort, a letdown considering this is a casual shoe intended for all-day wear.

Adidas Racer TR21 Tongue padding
Test results
Racer TR21 2.9 mm
Average 5.6 mm
Compared to 289 running shoes
Number of shoes
0.5 mm
Tongue padding
14.2 mm

Heel tab

We're always fans of heel tabs, serving as both style-enhancers and practical aids for sliding your feet into the shoe.

This model features a finger-loop heel tab, which earns our praise—it's a cool-looking detail!

Adidas Racer TR21 Heel tab
Test results
Racer TR21 Finger loop

Removable insole

The insole isn't glued down. This means you have the flexibility to swap it out with custom orthotics or an insole from another shoe.

Adidas Racer TR21 Removable insole
Test results
Racer TR21 Yes

Misc

Reflective elements

Finally, we're let down to report that the TR21 doesn't feature any reflective elements at all.

Adidas Racer TR21 Reflective elements
Test results
Racer TR21 No