Xero Shoes Speed Force II: análisis y review

We loved testing the Xero Shoes Speed Force II in the lab and found it’s perfect for:

• Runners looking for a minimalist shoe with exceptional ground feel and no midsole, for a raw barefoot experience.
• Those transitioning from zero-drop cushioned shoes like Altra to true minimalist running footwear.
• Midfoot and forefoot strikers who want a well-priced model that performs consistently on both pavement and dirt roads.

We found that the Speed Force II falls short in comfort compared to the Xero Shoes HFS II, which features a padded upper and thin midsole. The minimalist upper and lighter build of the Speed Force II are excellent for fast running, but they come at the cost of reduced cushioning.

For those transitioning directly from regular running shoes, we believe the Speed Force II may be too extreme. We think that a better approach is using a low-cushioned, zero-drop shoe like the Altra Escalante Racer 2 for a gradual transition before diving into the raw barefoot experience of the Speed Force II.

Xero Shoes claims a 7 mm stack height, but we measured 10.6 mm in the heel—slightly more than expected. However, it’s still firmly within the minimalist category and, in our view, better for most runners, particularly heavier ones who benefit from extra separation from the ground.

The forefoot measured nearly the same at 10.5 mm, offering excellent ground feel and encouraging foot strength with every stride. With no midsole and such a low stack height, your muscles and tendons must step up and take charge.

This shoe follows minimalist design principles and is marketed as zero-drop—but is it truly?

We tested it and found only a minor 0.1 mm deviation. In our view, this precision ensures a flat platform that aligns perfectly with the expectations of minimalist footwear enthusiasts.

The insole is the only real cushioning in this shoe, measuring 3.9 mm thick. We also discovered that its unique design, featuring hundreds of holes instead of a continuous layer, plays a critical role in achieving flexible movement and enhancing breathability.

Referring to the insole’s impressive flexibility, our photo for measuring the rocker unintentionally captured its cutouts perfectly. This creative design—rarely seen in other brands—significantly enhances flexibility.

As for the rocker, there’s little to mention. The shoe features almost no curvature, as expected and preferred in a barefoot-style running shoe.

The toebox is anatomical, which felt fantastic from the moment we first put the Speed Force II on.

However, the widest part of the toebox measures 98.5 mm—similar to an average running shoe—a fit we appreciate in a speed training shoe. We feel the same about the low-volume upper—perfect for speed and ideal for those who enjoy a snug, sock-like fit.

Where the anatomical toebox truly shines is in our second measurement—an impressive 87.4 mm!

We discovered that it provides mansion-like space for toe splay, allowing us to move our toes freely and comfortably. This design also enhances foot stability while running, aligning perfectly with what we believe a minimalist shoe should deliver.

All minimalist shoes lack stability features, requiring runners to engage their stabilizer muscles and tendons. While this can be beneficial, it’s not for everyone and can lead to injuries for those lacking the required strength. Therefore, please proceed with caution, especially if you have pronation or supination issues, as this is serious territory.

With no midsole and a design focused on flexibility, we fully expected minimal torsional rigidity—and that’s exactly what we found. Look at how we twisted it, absolutely ridiculous, that's a clear 1 out of 5!

The heel counter is another major change from the HFS series. While the HFS II features a more traditional running shoe design, the Speed Force II offers a super-flexible, counter that provides almost no resistance despite bouncing back to its original position, scoring another 1/5.

The forefoot (108.2 mm) may not be broad compared to the average running shoe, but for a minimalist design, we found it surprisingly generous.

In our experience, this makes the Speed Force II perfectly suited for forefoot and midfoot strikers—precisely the landing zones essential for a shoe with this barefoot-like design.

The heel is impressively narrow, evoking a ferocious feel reminiscent of track spikes and maybe only a handful of racing shoes like the Adidas Adizero Takumi Sen 10. Back in the lab, our calipers confirmed it with a crazy 73.0 mm measurement.

The foundation of minimalist running shoes demands exceptional flexibility for a natural, barefoot-like feel while walking or running, and the Speed Force II excels brilliantly in this regard.

We tested it with our 90-degree bend method, as we do with every shoe, using a force gauge to measure resistance. We had to be extremely careful, as it required only 3.3N to reach the desired point. That’s incredibly low, with the shoe bending as gracefully as a yoga master. For context, the Xero Shoes HFS II scored 10.5N—over three times as much!

We repeated the test after placing the shoe in our freezer for 20 minutes to simulate super-cold weather. While the flexibility changed by 27.4%, increasing from 3.3N to 4.2N, we can confidently say the difference is imperceptible.

One of the main challenges with Xero Shoes' minimalist footwear is the weight, which often feels heavier despite the absence of a midsole or the use of a very thin one. With the Speed Force II, this issue is less pronounced, as it weighs 6.7 oz (189g), but it's still here.

That's why we believe there’s still significant room for improvement—especially to bring the shoe below 6 oz, which would make it an even better option for speed training.

After testing, we discovered that the Xero Shoes Speed Force II excelled in ventilation, earning an impressive 5/5. The upper’s ability to let air flow cleraly stood out.

We also inspected the upper under a light to identify its most ventilated areas. The ultra-breathable mesh, combined with strategically placed thicker sections, provides durability and structure while effectively wrapping the foot for a secure fit.

Observing through our microscope, we found the upper constructed from a straightforward engineered mesh, similar to many others we’ve seen in various running shoes, featuring consistent ventilation openings throughout.

The upper is not built for comfort, featuring only a thin foam layer in the tongue and heel—far less than other minimalist shoes. This makes perfect sense for a model built for speed training and fast running, where weight reduction is key.

Uppers with exceptional ventilation often compromise on durability, but that wasn’t the case with the Speed Force II. In our view , the upper performed admirably, blending breathable-light construction with a surprisingly robust build.

Therefore, we gave it a 3/5 durability score in the lab—a result that surpasses many pricier speed training shoes. 

The heel scored a modest 2/5, which was a bit disappointing. However, we think that wear isn’t a concern thanks to the shoe’s superb lockdown, effectively minimizing heel slippage and reducing the friction that typically causes damage in this area.

Outsoles are crucial in every running shoe, but they’re absolutely essential in minimalist footwear, especially for those seeking versatility across multiple surfaces. The Speed Force II impressed us with its V-shaped lug design reminiscent of trail shoes, which shifts directions between the forefoot and midfoot to enhance traction on ascents and descents, especially during off-road runs.

In our first test, we found a hard rubber outsole measuring 87.5 HC on our durometer. That’s nice—you want to avoid soft rubber in a shoe without a midsole, especially when tackling easy trails or surfaces with small rocks.

However, we hoped for better durability from the outsole during our Dremel test. A 1.4 mm dent, measured with a tire tread gauge, left us slightly concerned about its long-term resilience.

Fortunately, Xero Shoes compensated with a thick 5.0 mm outsole—plenty of rubber to ensure it’s nearly impossible to wear down quickly enough to become an issue. However, we think it’s still a point Xero should address in future iterations.

We like the price of the Speed Force II, which is lower than the HFS series. While it offers less comfort, its has some upsides—like reduced weight and adjustable tension straps—that make it an appealing choice for fans of minimalist footwear.

Xero Shoes made the adjustable straps reflective, enhancing their utility. Hence, these dual-purpose straps not only provide a better fit but also add a safety-focused element. This is undoubtedly a brilliant addition!

One of the major differences between the Speed Force II and the HFS II lies in comfort—the former prioritizes weight reduction, while the latter emphasizes a cozier feel. Unsurprisingly, here we found a thin, performance-driven tongue measuring 2.7 mm, just slightly thicker than most racing shoes.

We found that the tongue is not fixed to the sides, aligning with the philosophy of most minimalist running shoes, which prioritize reducing weight and improving flexibility.

The heel lacks a tab, which makes perfect sense for the Speed Force II, as it incorporates a loop for the adjustable tension strap that goes through the rear of the shoe.

The insole is removable and features numerous ventilation holes, enhancing breathability even further—an amazing tiny detail that we couldn’t overlook.

One of the iconic features of the Speed Force II is the instep and midfoot tension straps, which are both stylish and highly functional, providing complete control over the lockdown. As you can see, they’re integrated into the lacing system and wrap around the shoe, allowing you to adjust the tension as needed.

Heading out for an easy run? Loosen them slightly. Ready for intervals? Tighten them up and push your limits!