Article by Sam Winebaum and Ernst Linder
Altra Experience Flow 2 ($140)
Highlights: The Experience Flow 2 is a moderate stack height 4mm drop 8 oz road training shoe with a new softer and bouncier EGO P35 midsole foam and anatomical foot shaped toe box. Altra joins the “fun to run” category with this model competing with shoes such as the ASICS Novablast and Mizuno Neo Zen.
Pros:
- Light: 8.0 oz / 227g US8.5 sample Sam / Ernst
- Moderate: 32/ 28 stack height with an appropriate 4mm drop Sam / Ernst
- No longer “firm and dated”: energetic: soft and bouncy midsole. Sam
- Upper: smooth fitting, broad anatomical toe box with solid midfoot and heel hold Sam / Ernst
- Altra zero drop loyalist well be happy : effectively zero drop due to soft foam but also not negative drop as a zero drop shoe likely would be with this foam
Cons:
- Needs more front response: wide toe box, softer foam, along with outsole rubber and design and shoe’s flexibility lack toe off snap at faster paces. Sam / Ernst
Introduction
With the Experience series of trainers Altra for the first time ventured above their traditional “zero drop” into 4mm drop shoes. I tested the Experience Flow 1 (RTR Review) and others on the RTR team tested the door to trail Experience Wiild (RTR Review). The Wild was a hit, trail favoring somewhat firmer and more stable rides while the Flow 1 was OK but quite firm with its foam what I called out in the review as dated and firm for a modern road shoe.
For the Flow 2 Altra goes with a softer foam called EGO P35. The “35” stands for the Shore A firmness measurement and 35 is, relatively speaking and compared to the prior Flow’s foam which I estimate to have been in the high 30's at least, is a soft foam. The "P" stands for a Polyolefin elastomers (POE) compound in the blend which gets the midsole some rubbery bounce.
Would it be a mushy and overly soft riding midsole was a key question. Even before running them I was quite sure that this softer foam would make the shoe on landings..a zero drop shoe! And not a “negative” drop if they had put the same foam in a zero drop geometry. While out in June, Altra had a few pairs for sale at the Boston Marathon and I purchased a pair.
Ernst: Being about 35 pounds lighter than Sam, yet with the same shoe size, I was less concerned about the softness of the foam, but more about whether the foam would inhibit my forward motion in up-tempo intervals, that I do frequently in daily training. I typically land at mid-foot and maintain a slight forward stance to take advantage of gravity (Chi-style), which creates a natural forward rocking movement. A small drop in stack height, such as 4 mm, does not seem to matter much for that purpose. Yet a larger drop could essentially alter my landing to to be more “flat” from midfoot to heel, and thus inhibit the natural rocking motion and toe-off.
Generally preferring light shoes with anatomical toe box of at least 110mm width, I have graduated from the more minimalist road shoes, such as the Altra Torin 4, to racers, such as the Topo Cyclone series. I am still trying to adapt to the newer foam and larger stack heights of today’s shoes. The Altra FWD Experience (RTR Review) and the Topo Specter 2 (RTR Review).are two of the more recent daily trainers that I enjoy very much because they promote the forward motion and toe-off naturally via their geometry.
Most comparable shoes
361 Eleos
ASICS Novablast 5
Stats
Spec Weight: men's 8.2 oz / 232g
Sample Weights:
men’s 8.0 oz / 227g US8.5 sample (v1 8.02 oz / 226g US8.5)
Stack Height: men’s mm 32 heel / 28 mm forefoot (4 mm drop)
Platform Width: 90 mm heel / 75 mm midfoot / 110mm forefoot
$140. Available June 2025
First Impressions, Fit and Upper
The design makes a statement that the Flow 2 is not a flat on the ground zero drop shoe. Not only do we have a 4mm drop but the “bathtub” rear midsole sidewalls which seat the foot into the platform convey a distinct visual sense of a ramp down and speed. And yes at its light weight of just over 8 oz and relatively low stack height of 32/28 we have a very light daily trainer with a focus on faster runs.
Ernst: For my body weight, I would prefer a more pronounced “bathtub” definition also in the front.
Sam: The upper is a dense but relatively thin engineered mesh reminiscent of recent ASICS such as the Magic Speed 4 if a bit thicker and less pliable and stretchy. It is a bit softer than the similar mesh in v1 which was flatter in profile
The mesh provides a consistent very solid hold with the gusset tongue, medial rear overlays and quite thick lacing loop array further ensuring mid foot lockdown.
The very high semi rigid achilles collar and semi rigid heel counter provide excellent rear hold and comfort with the collars moderately padded.
The rear is further stabilized by the foot sitting down into the midsole side walls.
All of this hold and stability is important given the softness of the midsole foam and relatively low 4mm drop as there is no sensation of mushiness, low heel, or instability even at slower paces (which the shoe can handle) while at faster paces the upper and geometry at the rear had me easily directing to transitions off the heel. Really well done.
The front of the shoe of course features Altra’s trademark Foot Shape toe box, here in the “Standard” shape/width and as always. and in particular here, given the uptempo nature of the shoe I am glad not the “Original” fit such as in the Lone Peak trail shoe which for me is only viable for walking and hiking.
Ernst: It takes me some effort to put on the “Standard” shaped shoe, and it feels cramped at first. But after a solid tying up, my feet settle in nicely and there is no discomfort because of the soft and nicely pliable upper. I was very impressed on a first leisurely run about the overall comfort that I felt was provided by the shoe’s design, it’s upper, and its snug fit. I agree completely with Sam’s descriptions on these features.
The toe bumper is surprisingly high, rigid and extensive for a light trainer and raises the upper “off” the foot more than ideal for my lower volume feet, although wider higher volume feet should be thrilled.
Ernst: I definitely need the provided vertical upper volume!
Sam: In combination with the soft foam and relatively soft and segmented outsole rubber I wished for a bit more lockdown up front (a lower toe bumper or maybe less vertical upper volume) as I felt my toes were not fully engaged and down at toe off as my paces picked up.
The fit is for sure true to size for me with of course plenty of toe box room.I might even consider sizing down half a size to improve the forefoot hold.
Ernst: Very much true to size for me as I have very wide feet.
Midsole & Platform
Sam: The star of the shoe, and most significant upgrade, is the new EGO P35 midsole foam. The previous Flow and quite frankly most recent Altra with their various flavors of EGO have increasingly felt dated and dull with the proliferation of supercritical foams now moving from racers to trainers.
The P in “P35” compound is a POE Polyolefin elastomer and we do know the “35” stands for the foam softness measurement and 35 is a relatively soft foam.
It feels quite a bit like the latest FF Blast foam in the Novablast or Salomon’s earlier Energy Foam.
Depending on the proportions in a blend can be less bouncy in feel, a bit more taut and rapid responding than what we have here, the Fuel Cell in the New Balance Rebel v4 an example.
Yet these blends can also be bouncier and energetic and the shoe that for me is the closest in feel to the Flow 2 is the 361 Eleos (RTR Review which does have an EVA/PEBA blend.
The big difference between those previously mentioned shoes (except the relatively low stack height 36/30 Eleos) is that here we have a lower stack shoe at 32/28 whereas the others are all pushing 40mm or more at the heel with higher drops. The platform is decently but not excessively broad at 90 mm heel / 75 mm midfoot / 110mm forefoot, the 90mm heel helping with rear stability given the soft foam. The platform widths are the same as v1 except the midfoot which is 5mm narrower.
The resulting combination of foam, stack height and platform delivers a flexible and fun ride with lots of smiles and energy. There is plenty of cushion here at the heel if a bit lower than we are growing accustomed to in the last couple years. So best to focus on a mid to forefoot strike pattern and faster daily training paces and you will have it in its sweet spot. The 4mm drop, please keep it Altra and especially with a softer foam I never felt I was going negative drop, even at slower paces.
Ernst: During a recent run - the shoe had about 75 miles on it - I tested the acceleration potential, and felt somewhat heavy and glued to the pavement. It appears that I am too light-weighted at 135 lbs to feel the softness of the foam or to experience the optimal ride and bounciness that Sam mentioned.
Outsole
Sam: Continuing my last thought about the heel landings with the soft foam and low drop, the rear outsole coverage is expanded over v1 with essentially coverage of the entire heel area of and, despite the color differences, a single firmness rubber.
Altra Experience Flow v1 Outsole
I note an added rear further forward triangle of rubber on the medial side which helps with a touch of pronation support there.
Ernst: I welcome this feature as pronation can be an issue for me.
This coverage is key to not only durability but also to disperse forces and respond on heel landings without the heel overly collapsing due to the soft foam above. It all works well with a lively rebound off the heel and quite easy any pace transitions.
The middle part of the shoe has no outsole coverage This, in combination with the lowish stack, makes the Flow 2 very flexible at midfoot with the front of the shoe stiffer but still with some flex.
The front outsole design follows Altra’s usual toe bones aligned approach with longitudinal strips of what feels like a slightly softer rubber than at the heel. Upfront (as with the upper) is where Altra might tune.
The soft foam, outsole rubber and converge could use more toe off snap and response. At easier paces everything is just fine but as the pace picks up i wished for a quicker front return on toe off. Everything is pleasant but not quite as dynamic as I wished for. Might be time to reconsider the long strips of rubber design for these softer foams.
Ernst: I found that the outsole works very nice on moderately technical trails in dry conditions. For roads, I agree with Sam’s concern about lack of dynamism at faster paces. Yet for me, I believe a more curved rocker geometry of the platform would be necessary to improve the dynamics and swift toe-off and return.
Ride, Conclusions and Recommendations
Sam: Altra has of course been well known for “Zero Drop” and Foot Shape fits but less so in recent years for exciting modern riding road trainers. The earlier Experience shoes had them successfully going to a 4mm drop which for many runners (and me) was an easier first step to zero drop and quite frankly I think a more commercially viable approach as well as zero drop shoes are no longer the rage as they were 10 years or so ago.
While the Experience Wild door to trail was very well received by our testers as its denser firmer EGO foam was better suited to the needs of the trail, the road versions were light but comparatively dull and dated due to their midsoles.
With the Flow 2 Altra scores! Of course the anatomical Foot Shape fit continues and should please broader higher volume feet, and the 4mm drop is noticed in a good way at all paces and even slower ones.
The key change is the new P35 foam which puts the Flow 2 squarely in the popular what I would call “fun to run” category with shoes such as the Novablast, 361 Eleos and new Salomon Aero Glide 3.
Energetic, flexible and bouncy, its upper is secure and comfortable. It is relatively stable due to its moderate stack height and geometry and has some well cushioned ground feel something increasingly missing in giant stack height rigid trainers.
I would like to see the forefoot stiffened and firmed up a bit, potentially with a different outsole design or rubber for more toe off response at faster paces as, in combination with the roomy upper, I felt I was not getting the full locked down drive to toe off impulse I believe the foam and platform can deliver and which could improve its range to faster tempos and even plateless racing given its 8 oz weight.
If you are looking for a light and energetic daily trainer with a lower drop that is fun to run and has a broader toe box the Experience Flow 2 is a top 2025 choice.
Sam's Score: 9.25/ 10
Deductions for lack of toe off response/snap at faster paces due to soft foam, flexibility and outsole design
😊😊😊 1/2Ernst: I do need a wide and high enough toe box to accommodate my big feet. After years of running uncomfortably in standard width shoes, I was steered to trying the Altra brand, and ran in two pairs of Torin 4’s each with about 1000 miles use on roads and also trails, training and racing. I continued with the brand, as well as the Topo brand during last 5 years with a strong preference for their lighter shoes.
The Altra Experience Flow 2 is the newest in a rapidly evolving development towards more comfortable, higher stacked, but light-weight all around trainers. I very much appreciate the comfort provided by the Flow’s design, as well as the overall quality of details that provide stability and a “smooth ride”.
I agree with Sam’s overall assessment. Yet, for a light-weight person like me, I would prefer a platform that better enhances the natural rocking movement from landing to toe-off thus providing more dynamics for faster tempos. As such the shoe would be have potential especially for recreational racers for large distance events.
Among the Altra models that I have used recently, for up-tempo purposed, I would rank the Flow 2 between the Torin 7 (lower ranked) and the FWD Experience (higher ranked).
Ernst: 8.7 / 10 8 * 0.5 + 10*0.3 + 9.5*0.15 +5*0.05 = 8.7
(Reduction for lack of dynamic forward motion; don’t care too much for white)
😊😊😊😊
5 Comparisons
Novablast 5 (RTR Review)
Sam: The ASICS has a similar riding foam and more of it as it weighs 8.75 oz / 247g in a US9. It a more max cushioned 41.5mm heel 33.5 forefoot stack height to the 32/28 in the Altra. Both have roomy toe boxes and are true to size. I prefer the more flexible, agile and lower geometry of the Altra for shorter runs and the added cushion of the ASICS for longer runs.
361 Eleos (RTR Review)
Sam: The Eleos is the most similar shoe in my view. Somewhat higher stack at 36/30 but still moderate for 2025, it sits on a considerably broader 100 mm heel / 85 mm midfoot / 120 mm forefoot platform. It has s a very similar riding energetic foam. The broader platform makes it less agile than the Flow although I find its stiffer more rocker based profile more responsive up front on toe off. Its upper is true to size as is the Flow’s with plenty of toe box room but lags in hold compared to the Altra’s as it is baggy and overly soft and pliable.
Altra Torin 7 (RTR Review)
Ernst: The Torin Is a slightly heavier daily trainer that weighs 8.95 oz / 254g men's (US9). It is zero-drop with stack height 30mm. I found the Torin 7 to be even less responsive in terms of landing and push-off than the Flow2. Overall a not very inspiring shoe with some design flaws: I had both the heel and the lateral ankle bone rubbing against the achilles collar and the heel counter, respectively. I suppose that could be remedied somewhat by using a heel cushion. Similar in price range.
Altra FWD Experience (RTR Review)
Ernst: It is the lightest of these newer models with weight: men's 7.7oz / 218g (US9). Like the Flow 2, it comes with a 4mm drop with stack Height: men’s 32 mm heel / 28mm forefoot , and a sticker price of $140 (2024). This has become one of my everyday favorite for tempo training as well as fun runs. I very much enjoy the distinct rocker motion that is built into the FWD experience through its geometry (see picture below). I have run 370 miles on this shoe and, in spite of a bit of initial tightness of Altra’s “Standard” width, I have broken in the shoe sufficiently for comfortable running. Overall, it does not show much of wear and tear.
I took a closer look at the structural difference between the FWD Experience and the Flow 2. It clearly lies in the geometry of the platform.
The FWD Experience (above) has a short ground contact length of between 2.5 - 4 : some of this may be due to usage has a ~ 1 inch heel above ground distance and a roughly 1.5 inch toe above ground distance.
The Flow 2 (above) has an 8 inch ground contact length with about ¾ inch heel distance from ground and about 1 inch toe distance from ground. This type of geometry is comparable to that of racers such as TOPO Cyclone and others.
Topo Specter 2 (RTR Review)
Ernst: Very similar in weight to the Flow 2, with US men’s 9 at 8.3 oz / 235g and women’s sample US 8 at 7.8 oz / 221 g, Stack Height is men’s 37mm heel / 32mm forefoot ( 5mm drop spec). It has a curved Pebax midsole that creates a distinct rocker motion; wide toe-box and a higher arch definition than Altra’s. It has received high ratings from the RTR reviewers. Its outsole is less structured and geared towards racing with minimal hard rubber coverage for traction. Yet reviewers found its outsole to be sufficient for protection on gravel. This has become my all-time favorite daily on-road trainer after I had broken it in for about 100 miles.
Tester Profile
Ernst lives on the New Hampshire Seacoast area and loves being able to run "from his doorstep" on several connected trail networks. While being the shortest student in grade school, he found almost all sports to be overly challenging, but "distance" running seemed to be natural for him. Eventually his family steered him towards competitive orienteering in his teenage years in Switzerland. This all stopped when he became an exchange student and moved to the USA.
But the seed was sown, and eventually the running spirit reemerged. Throughout the years he has rediscovered orienteering, pursued road, trail and mountain running, adventure racing, triathlon and nordic skiing.
He turned towards more competitive running when Loco started organizing races in the Seacoast area, first half marathons in 2007, and later marathons. His marathon PR is 3:03 at age 59, and he has numerous USA Track and Field New Hampshire age group state records. He is 70 years old 5ft 5 inches (165cm) tall and weighs 135 lb (61 kg).
Sam is the Editor and Founder of Road Trail Run. He is in his 60’s with 2025 Sam’s 53th year of running roads and trails. He has a decades old 2:28 marathon PR. These days he runs halves in the just sub 1:40 range if he gets very, very lucky. Sam trains 30-40 miles per week mostly at moderate paces on the roads and trails of New Hampshire and Utah be it on the run, hiking or on nordic skis. He is 5’9” tall and weighs about 160 lbs, if he is not enjoying too many fine New England IPA’s.
Europe only: use RTR code RTR5ALL for 5% off all products, even sale products
3 comments:
Saw a preview of this shoe on YouTube with Alex filitti and the Altra rep stated the P stood for PU, something that was in the old brooks levitate I believe.
Could be but PU is generally a heavy compound.
How would this compare to the Rebel v4?
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