Stan's Flow MK4 Review

Stan's No Tubes has been at the forefront of tubeless technology since 2001 when they figured out how to replace inner tubes with latex sealant. Since then, they've grown into a powerhouse of innovation and design building rims and wheel sets for almost every flavor of off-road use. The new Flow MK4 wheelset features Stan's M-Pulse ultra low drag hubs that employ a magnetic pawl system to provide incredibly fast and reliable engagement. Our testers have been impressed with the responsiveness and feel of the MK4 and find them wildly capable.

Performance Comparison

Product Specifications

The Stan's Flow MK4 is built with Stan's own Flow rim that features asymmetrical drilling and a reinforced spoke bed. The rims have a specially patented bead shape that Stan's calls BST or Bead Socket Technology that pushes the tire outward so the sidewall has minimal interface and thus friction, with the rim bead. The welded joint rims are crafted from 6069 alloy and have a low profile 30mm internal width. Externally, they measure 33.6mm and are intended for trail tires in the 2.3 to 2.6 width range.

Stan's has been hard at work on hubs to pair with their popular rims for many years and the new M Pulse hubs are an innovative step forward. A stated objective when building these hubs was to reduce drag that can be caused by free hub pawls while not engaged (that's the clicking noise we hear while coasting). Stan's clever solution was to use neodymium magnets that produce virtually no resistance when coasting, but lock the pawl teeth into place when engaged (more on that later). The hub internals are being manufactured by Project321 in Bend, Oregon, and the hubs are assembled in Stan's headquarters in New York giving them a bit more control over quality than having the hubs made entirely overseas. A unique feature is their external bearing preload adjustment that allows the user to fine-tune the hubs to provide minimal resistance.

The wheels are laced with 32 Sapim double-butted spokes, alloy nipples, and are offered with Shimano HG, Sram XD, and Shimano Micro Spline freehub bodies. Center lock and 6-bolt rotor configurations are available, and the wheels come with tubeless tape and valve stems installed.

Ride Quality

The Flow MK4 wheels have a lively ride quality that feels snappy and accurate. They offer precise handling and above-average stiffness for their weight. Stiff enough that we'd recommend them for ripping fast berms or use as a race wheelset. While they do feel efficient and responsive, they're not the most comfortable, these wheels transmit a fair amount of vibration to the rider.

We found Stan's claims that the hubs were fast rolling to be on point, the magnetic freehub and micro-adjustable preload create very little friction to slow your roll. We never experienced any chain drag or lag from the system. Response was direct and gave the wheels a really high-performance feel. There was a similarity in ride quality and overall stiffness between these wheels and the Enve AM30.

Freehub Engagement

The M-pulse hubs boast 1.66-degree engagement which is quicker than anything in our current test but a fraction of the previously tested Industry Nine Hydra at 0.52 degrees. The magnetic pawl system offers more than just fast engagement though. The neodymium magnetic pull springs are at their strongest while the pawls are engaged while a traditional pawl spring system is strongest while coasting decreasing the efficiency of the system as the pawls push against the drive ring. Stan's claims this system is not only more efficient but also more reliable and consistent than the springs used in traditional free hub mechanisms. We can vouch for the efficiency of the system and while we had no issues with the freehub, we really can't opine on its long-term durability.

Increasing the level of engagement, while a useful metric isn't necessarily discernible to every rider nor will it translate to a huge jump in performance. What you will experience riding these wheels is a quick response out of corners, a faster reaction while ratcheting and an overall more refined drivetrain. The effect of the magnetic pull springs is that the wheel rolls efficiently and makes a more subtle coasting sound than found on many other wheels.

Weight

The Flow MK4 wheels are fairly lightweight for an alloy wheelset. On our scales, they weighed 1,919 grams with rim tape and valve stems installed. The Hunt Trail Wide wheelset for comparison weighs 50 grams less and boasts a higher rider weight limit. Despite them being a bit heavier they don't feel heavier while riding, the wheels have a snappy, stiff, and lively feel.

Durability

We treated these wheels like rentals, they arrived during perfect late summer conditions and took us all over the Sierra. They were abused on the red rocks of Sedona and put to the test in the talus fields of Tahoe. We rode them with Maxxis Minion DHF/DHR Tires at 23 and 25 psi and introduced the rims to trail surfaces on many occasions. At the culmination of testing, we pulled the tires and put them in the truing stand to discover that they'd held up remarkably well. The rims are still straight and round and the spoke tension is close to the original readings we took. They have a few scratches and scuffs but that seems normal for what they've been subjected to. We know that alloy rims can be dented and bent easier than carbon rims so we're impressed with their durability. Stan's lists a rider weight limit of 250 lbs for this wheelset, and while the hubs are approved for e-bike use, this wheelset is not. Riders looking to outfit their e-bikes with Stan's wheels should look to the Flow EX3 or Flow S2 models.

The hubs also seemed to fare well, a post-test inspection of the bearings and freehub body found no contamination past the seals and the bearings felt as smooth as they did on day one. Stan's warranty isn't anything to write home about but they do offer a low-cost crash/damage replacement program if you manage to make your wheels less than round.

Value

This set of alloy wheels isn't cheap, they're only a few dollars less than the Industry Nine Hydra S wheels that we absolutely loved. What this wheelset does offer is a new paradigm of ingenuity in an efficient package. If we wanted the best wheels for racing for less than a thousand dollars, these might be our pick. They offer a serious performance upgrade from most stock wheelsets without making the jump to carbon hoops.

Conclusion

The Flow MK4 is a compelling wheelset. The combination of precise handling, quick engagement, and low drag will make almost any bike feel quicker and more nimble. The stiffness of these wheels could be an attribute to those looking for their next podium or a detriment to those trying to stay comfortable in the saddle all day.