Stan's Introduces New MK4 and S2 Rims and Wheels

Jun 29, 2021
by Stans NoTubes  

New Wider, Asymmetric Rims and All-New Hubs
Almost 20 years after Stan Koziatek created his first tubeless-ready rims, Stan’s NoTubes is proud to introduce the new Crest, Arch, and Flow MK4 and S2 series aluminum rims and wheelsets. Full information is available here.

MK4 Rims and Wheelsets
Building upon their experience making asymmetric carbon rims that incorporate their patented Bead Socket Technology (BST), Stan’s developed the MK4s, their first asymmetric aluminum rims. The BST-Asymmetric design allows for an improved bracing angle and nearly equal spoke tension balance, while also maintaining the easy inflation and reliable airtight seal that have made Stan’s the leader in tubeless rim design. The new MK4 series rims are available in three updated widths. Each Crest, Arch, and Flow model has its own purpose-built, wider rim shape and spoke hole offset.


Stan's dedication to tubeless performance led to a total rethink of asymmetric rim design and resulted in wheels that are stronger overall than previous versions. In creating the new MK4s, Stan's addressed the issues that most traditional asymmetric wheel designs have, such as being more difficult to inflate, being more prone to air loss due to unequal bead retention, and being more likely to be dented by impacts. As a result, the new MK4 design gives balanced pressure along the drive and non-drive-side tire beads and consistent impact resistance on both sides of each rim.

Crest Arch Flow MK4 Rim Sections

Crest, Arch, and Flow MK4 rims are made of 6069 aluminum with a welded seam, have a reinforced spoke bed and walls, and feature a matte-blasted finish. MSRP in the U.S. is $129.00. MK4 rims include a three-year warranty with crash replacement support and are available now.

Crest Arch. Flow MK4 Rim Profiles

Built for gravel and cross country riding, Crest MK4 rims have an internal width of 25mm with a spoke hole offset of 1.5mm and are optimized for 40mm gravel tires up to 2.3” mountain tires. Offered in 20”, 24”, 26”, 27.5”, and 29” versions, the Crest MK4 rim weighs 374g for the 27.5” version and 399g for the 29” version.


Arch MK4 rims are the most versatile of all Stan’s rims and are ideal for a wide range of trail riding. They have an internal width of 28mm for 2.2-2.5” tires and an offset of 2.5mm. Available in 24”, 26”, 27.5”, and 29”, the 27.5” Arch MK4 rim weighs 451g, while the 29” version weighs 481g.


The legendary Flow rim has earned Downhill World Cup and Enduro World Series wins and is a favorite among gravity and trail riders everywhere. With emphasis on strength and durability, Flow MK4 rims have an internal width of 30mm for 2.3-2.6” tires. Available in 26”, 27.5”, and 29” versions, the Flow MK4 rim weighs 487g in 27.5” and 521g in 29”.

Thomas Vanderham on Vancouver s North Shore BC

MK4 complete wheelsets will be available in late 2021 and will feature an entirely new M-Pulse hub design that will be shared with all Stan’s high-performance aluminum and carbon wheels.


S2 Rims and Wheelsets
Like the MK4s, Stan’s S2 rims have also increased in width, but they are manufactured with 6061 aluminum using a durable sleeved joint and stainless steel rim eyelets, and they rely on Stan’s proven conventional symmetrical Bead Socket Technology for easy inflation. S2 rims come in the same widths and are for the same recommended tire sizes as the MK4 rims.


The Crest S2’s 25mm internal width is ideal for gravel tires from 40mm up to 2.3” mountain bike tires. The internal width of the Arch S2 is 28mm, and it is optimized for 2.2 to 2.5” tires. Flow S2 rims have an internal width of 30mm, ideal for 2.3 to 2.6” tires.


Well suited for eBikes, S2 wheels are built with Stan’s all new E-sync hubs to handle additional weight and drivetrain stress; they have a 47% increase in max torque load capacity over Stan’s previous Neo hubs. The new E-sync hub has reinforced pawls that distribute stress away from bearings, chromoly axles, and Enduro brand bearings, including a double row bearing in the freehub to maximize durability.


E-sync hubs provide fast 8.18º engagement, with all pawls engaging simultaneously to ensure reliable engagement under high loads. E-sync’s endcaps and freehubs are backward-compatible with Stan’s previous Neo hubs.

Crest Arch and Flow S2 Rim Sections

S2 rims are being spec'd on select complete bicycles, and S2 complete wheelsets will be available from independent bike shops and online stores in August. They will have an MSRP in the U.S. of $595.00 and include a three-year warranty on E-sync hubs, and a two-year warranty on S2 rims.

Crest Arch Flow S2 Rim Profiles

More information is available here.


106 Comments

  • 56 15
 Anyone else agrees that they need to make a better hub go with it?
  • 26 1
 Pulled from the article: "The new E-sync hub has reinforced pawls that distribute stress away from bearings, chromoly axles, and Enduro brand bearings, including a double row bearing in the freehub to maximize durability." and "E-sync hubs provide fast 8.18º engagement, with all pawls engaging simultaneously to ensure reliable engagement under high loads. E-sync’s endcaps and freehubs are backward-compatible with Stan’s previous Neo hubs."
  • 9 0
 "MK4 complete wheelsets will be available in late 2021 and will feature an entirely new M-Pulse hub design that will be shared with all Stan’s high-performance aluminum and carbon wheels."
  • 30 13
 @geronimok: Fast 8.18° Engagement? That is NOT fast...
  • 7 2
 You can just buy the rims and lace them with the hubs you want. I have had the Arch MK4 wheelset. Great wheelset. The Neo hubs were pretty good, but I do prefer other companies hubs.
  • 13 3
 Worst hubs I've ever tried. Rims were just OK but didn't last that long either....
  • 18 0
 @noakeabean: it works out to 44POE. Same as Hope Pro 4s. Not crazy fast for sure, but definitely fast enough for anything but trials and faster than all the OEM options that are typically 18-24 POE and even some high-end hubs like DT Swiss.
  • 7 6
 @big-red: Yeah true. Still wouldn't advertise it as FAST ENGAGEMENT 8°!
  • 4 0
 My friends rear hub that just exploded after 10 uses says yes.
  • 5 2
 @geronimok: is fast engagement hub even a good thing now with clutched cranks? Legit question here why not just have slow engagement hub and more active suspension?
  • 2 0
 @shredb4dead: 10, that sucks, I got at least 15 rides on the first one. maybe 12 on the replacement.
  • 1 1
 @donpinpon29: clutched cranks?.? What are those.
  • 4 0
 @tacklingdummy: Agreed. Just get these laced up to Hope hubs. That’s about as good a combo price, durability, weight you can get out there in my opinion.
  • 1 1
 @noakeabean: But it does mean you dont need one of those weird chainsets that removes the whole point of fast engaging hubs :-)
  • 1 0
 @noakeabean: O-Chain Active Spider
  • 1 0
 @noakeabean: Faster than a DT Swiss 240...
  • 5 0
 @donpinpon29: With a "Clutched Chainring" as you're referring to, the chainring allows for the same amount of give (in degrees) if there is a large compression. If you simply use a very low engagement hub, sometimes you may be at the optimal hub position where your hub soaks up the petal kickback, but other times your hub position may be that you get petal kickback. This unpredictability is what makes the O-Chain more effective. In theory, if you are using an O-Chain, there is no benefit to having a low engagement hub because it would be redundant in soaking up petal kick. You would be best off with a higher engagement if that matters to you. Hope that makes sense
  • 2 0
 @shredb4dead: I had an ongoing relationship with Stan's for a couple seasons pre-pandemic. I blew up every single hub they gave me within 200 miles. I'm 210 lbs, and def ride hard, but there's no damn excuse for the crappiness of their hubs, especially when their rims have arguably the best performance in the business. After I destroyed the fifth or sixth hub in a year I finally got tired of waiting for my next one to show up and built up a DT 350. 2000+ miles in, on its third rim and still going strong.
  • 1 0
 @gkeele: Not if you swap out the star ratchet to the 54. But honestly the ratchet is much better suited to the torque loads generated by today's massive cassettes. More points of contact means better longevity.
  • 1 0
 @donpinpon29: It doesn't work that way. depending on the position of the freehub you may have instant engagement (also kickback), or you may have several degrees of rotation before engagement... On average slow engagement probably helps suspension, but the inconsistency is the problem.
  • 29 7
 I wonder if these will crack at every spoke nipple like every MK3 and EX3 Flow I've ever used. Never Again.
  • 16 2
 This comment made me go look at the spoke nipple holes on my MK3. Found some cracks! How long until my wheel explodes?
  • 15 1
 Genuinely curious. Are you using a tension meter when you are building them? I've built piles of wheels on their rims and never seen any of them crack at the nipples as long as they are built with in the specs Stans gives for them.
  • 9 0
 @toddball: I have been riding for 2 years since I discovered a series of small cracks on my Arch MK3.
  • 11 0
 @lyfcycles: Same here. Have built many, with very even tension, usually a little below Stan's recommend max tension because I have noticed the MK3 spoke bed doesn't react as favorably when taken right to max. My own observation, YMMV. Have yet to see a crack in any of my own builds. I quite like the MK3 hoops.
  • 6 0
 @lyfcycles: I second this. I've built numerous wheels with Stans and have never had an issue. Maybe people are checking tension with the tire inflated..?
  • 14 0
 @lyfcycles: Agreed - I also have never had an issue. As you clearly know, a number of Stan's rims now have a spec for max tension at or north of 125 KgF (which is beyond the DT Swiss threshold, for those commenters who will, fairly so, bring DT's benchmark products into this conversation). Numbers aside, I agree that the modern Stan's rims are strong and will last if properly assembled. When rims crack at the spoke beds - certainly not always, but often - failing to use washers in the build or using straight-gauge spokes are the likely long-term culprits. Straight-gauge spokes take needed "suspension" forces away from the rim (and hub) material, expediting fatigue on the hoops as well as shortening the usable lifespan of the spokes themselves. And washers obviously spread loads better at the spoke holes, reducing the concentration of those large pulling forces on these critical flashpoints in the structure. (In doing away with eyelets on many of their rims, DT now supplies washers with their premium items - which is always welcomed and a smart practice that more companies should emulate.) Mix the build elements described here with really low tire pressures on non-gravity tire casings in a rugged MTB context and any rim is much more likely to fail, whether alloy or carbon. That Stan's rims are "soft" for tensioning purposes is an MTB canard that has now been superseded by better iterations of their product lines. These are quality hoops and have been for several years.
  • 9 0
 @thehighwheeler: Most people are most likely on machine built wheels and don't know the difference.
  • 11 1
 2 words: Nipple Washers
  • 1 0
 I ,like several other commenters here, have either run machine-built or hand-built Flow and Arch MK3 rims on several bikes over the last ~4 years without issue. Probably 9 wheels in total (including rebuilding smashed rear wheels from mega-casing sketchy jumps).
I will admit that the NEO hubs do need improvement; broken axles and blown up freehub bodies are not uncommon. However, when evenly and properly tensioned, I haven't had a single issue with rims cracking! I have noticed deformation around the drill for the nipple, but not a single crack. I do not use nipple washers either.
For what it's worth, I am very pleased with all of my Stan's wheelsets and rims, and when you do need warranty support, I have found that they are very easy to deal with.
  • 7 1
 @lyfcycles: complete wheel from Stans or Laced by me at home, doesn’t matter they all crack. Go check your Flow MK3s I’ll bet you a Double Double you find a crack.
  • 3 0
 @justinb03: That’s awesome they’ve lasted so well for you! I will say I’ve never had one taco or catastrophically fail but I’ve cracked maybe… 4 MK3 flows, and 1 EX3 Flow? People I know who ride the same area have had the same experience. Maybe our terrain plays a factor! Who knows. Hopefully these new designs fair better!
  • 5 0
 @justinb03: deformation around the spoke holes I have seen as well, over many rims/builds where people are not careful, and that's what I would be tipping my hat to when talking about not building right to max tension. E\With every wheel I build I am watching how the rim and spoke bed and area around the spoke holes is reacting to every round of increase in tension. Build enough of any rim and pay attention, and you'll see the tension any particular rim 'likes' is not necessarily the same as the recommended max. An experienced builder will pay attention to how a rim is reacting, not blindly bring tension to max and call it. If you build carefully/know what you are doing, Stan's MK3 rims are pretty good stuff.

On nipple washers, Stan's MK3 rims have fairly narrow drilling, 7.5mm holes, and the profiling of the spoke bed around the spoke holes means not all washers will fit or be compatible/work optimally. I have a couple I keep in stock that work okay/improve the situation somewhat, but neither will do the job that the DT PHR washers do inside DT rims; none will spread the load as well. I still build with them (washers), but I know folks who don't with the MK3s and also get on alright - the key is careful tensioning. Stan's MK3 spoke beds are not overly thick and it pays to keep an eye on them.

These new rims are interesting. Looks like a shot peened finish, and profile features that are entirely different that the MK3s. I would almost bet they are coming out of a different factory than the MK3s. Chatting with another rim geek here as well as I write this, who has pointed out they look a lot like WTB Asyms, in the smaller details. Pure speculation on my part, but I would wager they are made being produced somewhere different than the MK3's, so perhaps the conversation on cracking older rims is a moot point.
  • 3 0
 @privateer-wheels: Ever tried sapim MG washers? Those look like perfect solution to this "issue" and should fit at 7.5mm OD. Same with every other rim with flat nipple bed.
  • 1 0
 I didn't have a single crack at a spoke nipple... mine completely separated at the weld seam instead.
  • 10 0
 @moonraker: I been trying to land that job for years
  • 1 0
 @squidvicious: be careful what you wish for Razz
  • 2 0
 Seen the same with several Flows and some crests that cracked at literally every single nipple hole
  • 2 0
 I've had a couple sets of flow ex and one flow mk3 all built by a very good wheel builder (Dave Thomas). They were all great wheels.
  • 3 0
 @toddball Next ride mate
  • 2 0
 I had the same problem until I started building my wheels softer. I read Jobst Brandt's book "The Bicycle Wheel" and it totally changed my approach. Still, those rims don't take side load all that well, and they should be better.
  • 1 0
 @lyfcycles: It's usually that they crack as people try to true them straight again after a while and go over tension. The way the eyelets are machined don't hold up to heavy side loading.
  • 1 0
 @privateer-wheels: Exactly. Once I started building them under tension spec they held up MUCH better.
  • 2 0
 @adamszymkowicz: be careful, I never said I built them 'under-tensioned', to be clear. I still wind up inside a perfectly reasonable band of tension, just not as high as the stated maximum.

Just aiming for max is a fools method of building. IMHO you need to bring tension up in stages, stress relieve and watch how the rim is responding. Often the rim will tell you when to stop, before you hit max.
  • 2 0
 @moonraker: Whoever downvoted you doesn't build their own wheels.
  • 1 1
 @devin-m: If you're right he has to drink that pig-swill Tim Hortons coffee right?
  • 1 0
 @squidvicious: I did that job... granted it was dairy cows, but double the nipples double the fun.
  • 2 0
 @nzandyb: Its more of a punishment than a reward!
  • 2 0
 @westeast: I’m still running Flow Ex rims on one bike and they are fantastic. Zero issues. The MK3s just aren’t up to it for me.
  • 1 0
 I am a shop mechanic and have built on all sorts of rims, have had more Stan's crack than any other brand. Built up to proper tension evenly and carefully. Sure washers can help but then you're adding a fair bit of weight to a lightweight rim, when you can go to a slightly heavier rim that will be much more durable and not have to deal with nipple washers. I've been a fan of Chromag Phase 30's. Only slightly heavier and way stronger.
  • 1 0
 @privateer-wheels: cracked 3 stans flow all hand built to proper tension...would not buy again. On ex471 and have been very impressed
  • 1 0
 @moonraker: cracked with them
  • 20 1
 Good. But I will stay with DT Swiss and Newmen.
  • 19 2
 Just job out your hubs to Hope and be done with it.
  • 21 0
 Stans rims on hope hubs seem like the best setup in this price range by far
  • 6 0
 @McSmuggin: Given the issues I have had with Hope bearings failing in multiple rear hubs, it hardly seems like a solution. I am not alone. Beautiful hubs, great machining, let down by garbage bearings.
  • 1 0
 @carym: Cracked multiple drivers over here.
  • 4 0
 @carym: they are common sizes though and easily upgraded...
  • 1 0
 @carym: agreed, pretty trash hubs in my experience. But colours and pb fanboy points count for something? Right?
  • 1 0
 @bonfire @carym what do you like better at that price point? What’s your go to workhorse hub?
  • 3 0
 @speed10: dt swiss 350 - cheap, reliable, serviceable, light enough, fast enough.
  • 2 0
 @ohio: DT Swiss stuff is just too good. The 350 hubs are faultless and I've been pretty happy with my EX rims. Still put a few flat spots in them but short of going to carbon someone would have to make a definitively equal quality rim for 2/3 the price for me to even consider switching.
  • 17 3
 And are they going to make a hub that doesn’t blow up after two months?
  • 5 3
 Sounds like you’re hard on rims.
  • 2 0
 What tipped you off? Doing dumb stuff on hardtails takes a toll on gear.

I had a stan’s flow mk3 wheelset and the bearings blew up every 2-3 months until they eventually sent me a replacement wheel with a hope pro 4. Great customer service from them, just terrible hubs
@extratalldirtrider
  • 2 0
 @dentedrims: Trying to ride chunk fast on a hardtail is rim suicide. I'm sure the hubs are as bad as you say though.
  • 11 0
 Thanks for making them in 26"
  • 1 0
 Otherwise other brands like Alexrims still make 26' rims as well, especially for enduro/DH, like the Supra35 alexrims.com/products/supra35
  • 1 0
 @zoobab2: piggy backing on this, Alexrims DM24 is sick for DJ stuff
  • 8 0
 I haven’t had any problems with my Neo hubs. Of course I have swapped out the aluminum rear axle for a steel one.
  • 9 1
 Will these be made out of dehydrated cheese as well?
  • 2 0
 $130 is pretty pricey for an aluminum rim that isn't Newman or DT Swiss. I will give Stan's this much, however, offering a 3-Year warranty seems like a good move.

By comparison, you can get Newman 30mm wide 510g 32h rims for $90ish USD.

A DT Swiss EX511 is $140ish, but includes nipples. 570g.

As mentioned elsewhere, Ibis was selling their S35 for $100 and it was decently light.

Spank rims of similar weight and width are $90-$99.

Easton/RF Arc rims seems to be the bottom of what's decent and they can be found around $80.
  • 2 0
 I ordered new Stan rims this season and huge disappointment. Blackspire were half the price and lasted two seasons. I went on a first ride on stans and I could hear cling cling on the traiI. Also will be passing on stans. Overpriced for sure.
  • 3 0
 Maybe pinkbike make a wheels Wednesday to remember all of us wheel building tech, types of spokes crossing lacing applications. Types of rim hubs etc etc etc
  • 2 0
 This is the 3rd or 4th "all-new" hub from them. Every generation prior was just average at best, hopes aren't high that these will be any different.
  • 1 0
 RIGHT!?
  • 1 0
 They are trying to catch up to Zipp and Glock in versions of perfection.
  • 1 0
 Just checking in with some cracks on the eyelets of my Mk3 rims. Now running Newmen, and no such issues... Yet. I have yet to ride a rear rim for longer than a season (big and clumsy).
  • 1 0
 newmen uses very good washers designed to avoid cracks around nipple holes.
  • 1 0
 Looks like exclusivity on the asymmetric design they make for Ibis ran out. Seriously, the Ibis S35 slots right in as the next wider rim beyond the new Flow but Ibis only charges $100 for it (when it’s in stock).
  • 8 6
 28mm internal?? That is utterly unrideable, a liability if you ask me. People may die.
  • 3 0
 Nice to see that the graphics seem more subtle.
  • 1 0
 I think that Stan should make special rims/wheels called F U Spec in memory of a great success which was winning with that company.
  • 2 0
 Those are quite light rims, i wonder how they hold up
  • 4 2
 Sorry, never again Stan...
  • 1 0
 How does the new MK3 design give "consistent impact resistance on both sides of each rim"?
  • 2 0
 Yeah, this is what I am most curious about, because it's the biggest downfall for a lot of asymmetric rims.
  • 2 0
 Thank you Stans for making them in every size including 26"!!!
  • 6 0
 Yep. We got you covered.
  • 2 0
 Nice, 24” ain’t dead.
  • 2 0
 Truth.
  • 2 0
 Haha, I'm not a sucker. Stans, you will never fool me again.
  • 1 0
 Are the Flow and Arch similar strength (impact resistance)? Is the sole difference down to width?
  • 1 0
 Gonna come in handy for those NASCAR bike races going on everywhere.
  • 1 0
 Mountain bike velodrome?
  • 4 3
 How long they last until cracking?
  • 5 1
 Just don’t look at them too long
  • 1 0
 Available in 26 inch . Thank guys Smile
  • 2 2
 What is the benefit of asymmetric wheels?
  • 8 2
 Read the article?
  • 2 0
 By having the rim asymmetric it allows the drive/non drive side spoke angle to be the same, or at least closer to the same. The spoke angle being equal means symmetric spoke tension thus better lateral stiffness, well symmetric lateral stiffness.
  • 2 13
flag Peally (Jun 29, 2021 at 13:29) (Below Threshold)
 @kcy4130: So... it's a bunch of marketing and sales jargon.
  • 1 1
 @Peally: If you want a stiffer wheel, put a carbon rim on it. The benefits of asym are marginal.

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