Stan's latest version of their Flow wheelset uses an updated aluminum rim profile, along with an entirely different (and very clever) hub design. That second point will be welcome news to riders that had issues with Stan's Neo hubs in the past – those hubs weren't exactly known for their longevity.
There are 29” and 27.5” versions of the Flow MK4 wheelset, or you can purchase it as a mixed wheel setup – Stan's sells front and rear wheels individually on their website. The front wheel is priced at $308 and the rear is $657, for a total price of $965 USD.
The rims are covered by a 3-year warranty against manufacturing defects, although that won't cover you if you come up two feet short on a road gap. If that happens, Stan's has a 1-year crash replacement policy that gives riders 50% off a replacement rim. As for the hubs, those are covered by a 5-year warranty against manufacturing defects.
Stan's Flow MK4 Wheel Details
• Wheel size: 29" or 27.5"
• Intended use: trail / enduro / DH
• Rim material: aluminum
• Rim width: 30mm (internal)
• Hubs: M-Pulse, 1.66° engagement
• Rear hub spacing: 12 x 148 or 12 x 157
• Weight: 881 g (front) / 1039 g (rear) / 1920 g total (29")
• MSRP: $965 USD / rim only: $129 USD
• More info: notubes.com
The new Flow MK4 rims have an asymmetric profile, which makes it possible to use the same spoke length for the entire wheelset, eliminating the need to have multiple spoke lengths on hand just in case. Those 32-hole rims are constructed from 6069 aluminum, with a welded joint and a reinforced spoke bed.
They're laced up to the hubs with a three-cross pattern using Sapim D-Light spokes and alloy nipples. I prefer brass nipples over alloy, since they're less like to round out during truing, but they're not as common on pre-built wheelsets these days. The internal rim width is 30mm, a number that's pretty much become the norm for trail and enduro wheels, since it works well with tire widths from 2.3” to 2.6”.
What makes the new hub stand out is the use of magnets on each pawl. Small circular neodymium magnets pull the 6 pawls upwards into the drive ring, a design that Stan's says provides better engagement with less drag. And yes, it's based on Project 321's design – the Oregon-based company manufactures the freehubs for Stan's. Personally, I'm a huge fan of the fact there aren't any miniature springs underneath each pawl, since those seem to pop off and bounce into the darkest recesses of my shop exactly when I don't want them to.
The 6 pawls are oriented so that two at a time engage with the 72 tooth drive ring, which equates to 216 points of engagement, or 1.7-degrees of rotation between engagment. In other words, there's minimal crank rotation to engage the hub. It's not as quick as I9's Hydra hubs, which only have .52-degrees between engagement points, but it's not far off, and is up there as one of the quickest engaging hubs on the market. SETUP
This wheelset saw action in the wettest and the driest parts of the year here in Washington, so it's been exposed to the full gamut of mud puddles and moon dust. For the majority of the test period is was on a Stumpjumper EVO alloy, with a Maxxis DHR II DoubleDown rear tire and an EXO+ Assegai front and no inserts. My typical pressures were around 21 psi in the front and 23 in the rear, changing slightly depending on conditions. Tire installation was a breeze, and everything popped into place without any fuss.ON THE TRAIL
I've reviewed several different iterations of the Flow wheels over the years, and every time 'neutral' is the word that I end up using to describe the ride feel. They're not crazy soft or crazy stiff, which makes them one of those wheelsets that doesn't dramatically the ride feel of a bike. Now, 'middle-of-the-road' may not be a marketer's dream product description, but when it comes to wheels that's a good place to be.
Suspension and meaty tires do a lot to disguise wheel attributes, and it takes something dramatically different to deliver a tangible difference. Still, I could notice the slightly softer ride quality of these wheels compared to the carbon WTB CZR wheels I'd had on previously. Aluminum wheels tend to have a slightly more damped quality than stiffer (and more expensive) carbon options, and that was certainly the case here. There wasn't any harshness, and they were nice and comfortable on chunky, brake-bump filled trails.
This time around, it's really the hubs that are the main talking point. The fast engagement is most noticeable in slow speed, technical sections of trail, the type where you take a half pedal stroke here, and a half pedal stroke there. Whether ultra-fast engaging hubs are better than hubs with more moderate numbers is up for debate, but riders who are looking for a nearly instant response when stepping on the pedals will find a lot to like about the M-Pulse hubs.
Even with that high engagement the sound the rear hub makes when freewheeling isn't obnoxiously loud – it's audible, but not distracting at all. Riders that prefer super loud hubs could probably run a lighter grease or oil on the pawls, but for me and my sensitive ears the decibel level was ideal.
A rubber gasket on the non-driveside end cap would help improve the hub's water resistance.DURABILITY
The rims themselves have held up well, with only one small dent in the rear wheel after plenty of rough miles.As for the overall build quality, I did need to add more spoke tension after a couple days in the Whistler bike park. That's not uncommon, since those brake bumps seem to rattle pretty much anything apart, although I will say that historically I've had more Stan's wheels need attention than, say, DT Swiss wheels. The Flow MK4's don't have crazy high tension to begin with, so it's important to keep an eye on them, especially if you're doing a bunch of shuttle or bike park laps.
Most of the bearings are rolling smoothly, with the exception of the non-drive side bearing on the rear wheel. That one has developed rust around the perimeter, and is feeling a little gritty. Again, these wheels have seen some very wet rides, but I do think a rubber seal on that side of the axle could help improve the hubs water resistance.
Quick engaging, easy to service hubs.+
Very neutral ride feel – not too stiff or too soft
Spoke tension dropped dramatically part way through testing-
Hub sealing could be a little better for really wet conditions