Flat Out: 12 Racing Flats Reviewed

The fastest racing shoes for any distance.

This article originally appeared in the July/August 2012 issue of Inside Triathlon magazine.

Scientists confirmed what runners have intuitively known forever: Light shoes can be faster than heavier ones. Multiple researchers have found that increasing shoe weight by 3.5 ounces increases oxygen uptake—the energy needed to run a certain speed—by about 1 percent. Translated, this means shaving 3.5 ounces off a pair of shoes is equivalent to increasing your run fitness by 1 percent. The guys in lab coats have shown that light shoes can save energy, but finding the best race shoe for you is more complicated than leaving the running store with the lightest pair you can find.

Craig Alexander broke the Ironman Hawaii course record last October while wearing a pair of Newtons that are heavier than many racing shoes. He even used a plastic orthotic that further weighed down the shoe. The open marathon world record—2:03:38, held by Kenyan Patrick Makau—was also set in a pair of fairly sturdy shoes: the Adidas Adios 2.0 found on page 28. Alexander, Makau and many other long-distance runners have proven there’s more to race shoe selection than weight, and a recent lab experiment from the University of Colorado, Boulder, showed the same thing by demonstrating that a cushioned shoe saves energy compared to barefoot running. We tested the full spectrum of race shoes, from the New Balance RC 5000, which is one-third the weight of this magazine, to Mizuno’s sturdy yet responsive Wave Precision 12, to help you find the pair that best matches your stride and can help break your PR next time out, even if Alexander’s is out of reach.

Zoot Ultra Race 3.0, $150
Zootsports.com
Lace ’em up: For your fastest 5K or 10K time from T2 to the finish line
Find another: If you’re looking for a race flat built for speed only

The typical lift from toe to heel is shrinking for all varieties of running shoe to help promote mid-foot striking. That characteristic is great for typical training days, but a little lift can support bike-weary calf muscles. The Ultra Race 3.0 retains a fairly tall heel rise to help keep those muscles firing. The quick-close elastic upper provides a solid grip on the arch that “pleasantly surprised” one tester. The forefoot, however, created a little too much freedom for one tester’s feet, allowing them to slide side-to-side toward the end of longer runs.

Mizuno Wave Precision 12, $110
Mizunousa.com
Lace ’em up: If you’re looking for a snappy ride with cushioning
Find another: If you’re a hard-core minimalist

The Wave Precision 12 is much more than a sheet of cushioning separating your skin from the pavement; it is a structured yet responsive platform perfect for fast long-distance running. The sole provides a subtle degree of side-to-side stability, just enough to support fatigued post-ride legs. Unlike most shoes offering this degree of cushion, one tester said “it kicks me through a stride and never feels like a tether to the ground.” The airy upper allows the forefoot to move slightly. A tester with bunions raved that the additional forgiveness cradles his foot perfectly, but another found the lateral freedom creates blisters.

K-Swiss K-Ruuz 1.5, $100
Kswiss.com
Lace ’em up: If you want an agile, nimble shoe cut out for any distance
Find another: If you need rigid foot-to-sole connection

Take a standard cushioned trainer, shrink every essential feature—sole, stability gadgets, overlays on the upper—to the bare bones and you have the K-Ruuz 1.5. The sole is soft enough to take the sting out of the pavement, and the elevated heel—a full 10mm of rise from toe to heel—can work in favor of your fatigued calf muscles after the bike leg. Testers felt the sole, while plenty flexible in the forefoot, provides enough structure to lighten the load on the muscles of the foot. The upper stays remarkably dry but allows the foot to shift slightly on top of the sole, particularly at the heel.

Adidas Adizero Adios 2.0, $115
Adidas.com
Lace ’em up: If you’re a fast and efficient long-distance racer
Find another: If you want über flexibile shoes

The forefoot of the Adios 2.0 feels stiffer than a lot of racing flats, making it a safe choice for speedwork and tempo runs for slower athletes and a versatile half- or full marathon racing option for faster runners. This stiffness, plus the 11mm heel drop, may help with fatigue at the end of a longer race, but it likely won’t appeal to runners looking to make a move to pure minimalism. Testers noted the “just right” fit and springy feel as highlights, particularly during speed workouts. Also going for it is the fact that the Adios was worn during two marathon world records!

Asics Piranha SP 4, $110
Asicsamerica.com
Lace ’em up: For intense intervals and short races
Find another: If you want a tempo trainer or all-purpose shoe

The “barefoot” movement might seem new, but old-school runners have been using shoes just like this one to get the benefits of minimalism long before it became trendy. Testers said the shoe is meant for fast running and promotes mid-foot striking. “As you move farther up onto the toes, it becomes more responsive, more flexible and quicker off the ground,” raved one tester. Despite its shockingly low weight, the sole offers “a good blend of flexibility and stiffness,” and the upper provides a “snug, but not suffocating” fit throughout.

Brooks Launch, $90
Brooksrunning.com
Lace ’em up: If you’re a long-course racer with efficient mechanics
Find another: If you need pronation control

Now that the terms “stability” and “motion control” have become synonymous with “clunky” and “awkward,” shoe companies are quick to disassociate their cushioned shoes from those former buzzwords in favor of trendier terms such as “neutral.” The Launch, however, truly is an amply cushioned neutral shoe. Its soft and forgiving platform frees the foot more than most so-called neutral shoes of similar weight while preserving the snappy feel often reserved for firmer shoes. The toes have plenty of space to spread, and the rest of the foot is firmly secured in place.

Saucony Type A5, $100
Saucony.com
Lace ’em up: For a pure racer with just enough cushion
Find another: If cycling leaves your calf muscles spent

Snug as a glove with its light, breathable upper, the Type A5 is half an ounce lighter than its predecessor, and still offers just enough cushioning. Testers perceived the midsole to be “flexible and bouncy” while providing a minimal but effective barrier between the foot and the ground. Fashioned for a mid- or forefoot strike, the low-profile heel helps encourage quick leg turnover but isn’t robust enough for pure heel strikers. Designed with drainage holes throughout the sole and a loop on the back of the shoe to help slide the foot in for a quick T2, the Grid Type A5 is great shoe for sprint or shorter triathlons.

New Balance RC 5000, $125
Newbalance.com
Lace ’em up: For all-out speed burns
Find another: If you need any support at all

If you run with little weight on your heels, this crazy light racing flat is a specialized weapon for your fastest workouts and races. Its paper-thin sole provides a surprising amount of cushioning, substantially more than many minimalist shoes of similar weight. The upper tightly cinches the forefoot to the sole. The narrow forefoot squeezes down firmly on the metatarsal arch but only softly on the mid-foot and heel. When running up on your forefoot, the RC 5000 is the perfect match. “It softens the feel of the ground just enough and snaps off the turf,” reported a tester. Running at slower speeds, however, is a bit awkward. The shoe “squirms and twists” around the foot when running with a heel-striking gait.

On Cloudracers, $129
On-running.com
Lace ’em up: For a uniquely suspended minimalist ride
Find another: For unadulterated road feel

The shtick behind On shoes are the circular pieces of rubber that line the sole. This system is intended to absorb both the horizontal and vertical shock from running, and to activate as opposed to stabilize a runner’s postural muscles—helping to prevent injuries, On says. And while the tester obviously couldn’t verify this claim scientifically, he did notice that his recurring calf injury wasn’t aggravated in these shoes. This unique sole transfers the “feel of the road, without the shock,” said a tester. Despite the light and flexible forefoot, testers said the impact felt cushioned yet responsive, and never like he was sinking into the shoe as he ran. Testers found that the upper conforms securely to narrow feet.

Newton Motion, $175
Newtonrunning.com
Lace ’em up: If you want protection and support without sacrificing speed
Find another: If you aren’t accustomed to a low-profile heel (or the hefty pricetag)

Although Newton categorizes the Motion as a stability shoe, it qualifies as a racing flat by typical standards because of its “comfortable, flexible and responsive ride,” said one tester. Its pronation resistance is subtle, and the shoe’s external actuator lugs—the four rectangular pieces of rubber that stick out of the shoe’s midsole—are made to return the energy back to you. Our testers found this unique construction demands a mid-foot or forefoot gait, which they deemed perfect for fast training days and races. After several runs, the lugs felt natural.

Pearl Izumi W Streak II, $115
Pearlizumi.com
Lace ’em up: For the perfect balance of structure and lightweight freedom
Find another: If you want the lightest shoe possible

Responsive, snappy, agile and flexible are some of the words testers used to describe the Streak II. Although other shoes in this review drew similar praise, none of those also boast adjectives such as supportive, structured and resilient. The Streak II finds the “ideal balance” between a fast and free racer and a training shoe that shares the burden of running on tired legs. With just a tiny bit of arch support, they’re great for long, hard runs and 5K burns. Testers found the fit to be on the small side, tightly securing the heel and forefoot, which further adds to the responsive feeling.

Nike Free Run+ 3, $100
Nike.com
Lace ’em up: For a liberating yet comfortable cushioned racer
Find another: If your feet struggle to support themselves

Although the shoes are roomy, they securely connect with the foot, even when running on soft surfaces. “It’s almost like the shoe molds to your foot when you put it on,” said one tester. If you’re a mid-foot striker, you’ll notice that the Free Run+ 3 “provides just the right amount of support for your arches,” according to one tester. The famous Free sole offers more than just flexibility. “Its combination of responsiveness and cushioning makes it something you could be confident wearing if you wanted to PR in a sprint race or for a half-Ironman,” raved one wear tester.