Hard to tell, but it sounds like your issue is the freehub, not the cassette.

From your description of poor shifting, it's possible that the entire freehub might be slipping a bit, in which case the pawls might not engage. Make sure all the the hub nuts are appropriately tightented, etc. Hard to be more specific without knowing the type of hub, etc.

I thought the same when I read the OP.
Problem with the free hub.
Depending on the design, it could be something like the whole freehub not seated into the hub body fully, or that the spring(s) that force the pawls out are sticky. Some freehubs only use 1 thin wire spring to actuate all 3 pawls (shiiite design used by Campag, Fulcrum, some Specialized, and unsure what else) so if something imis getting sticky after some watery or dirty rides it could be that too).
(Not sure precisely what is on the Zipp wheels and from when(

Thanks for your response. Here's what kind of hub is in a Zipp NSW 808

The ZR1 features key technology from Zipp’s Cognition hubs. The seal design is the same as the Cognition, with a large dust cap at the base of the driver body and better bearing seals for more protection. The bearing size also is the same as the Cognition, although the Cognition uses a premium bearing. The six pawls are offset to work in two groups of three pawls. At any time, there are always three pawls engaging. This design creates a quick engagement feel, with 66 points of engagement. The driver body is designed so pawls stay in place for disassembly to make service convenient. Zipp hubs are designed to use J-bend spokes, the most popular type of spokes today. J-Bend, widely available, are easier to replace.

It rained a lot on the bike at Tulsa and my bike was a mess. But you would think when the bike shop checked it the first time it happened they would have cleaned out any grime and for sure the second time when they put on the new cassette.


I will take it to a different bike shop.

Hmmm NSW have the 'cognition' hubs with the axial clutch. Zipp claims it has lower mechanical resistance compared to pawls. Wondering if there's something wrong with it? Not sure. I've never taken one of those apart.

I would remove the freehub body and take a look at what's happening.

The bike mechanic said there are magnets that hold things in place with the freehub/cassette and if the wheel is not put on correctly and they don't line up correctly, they can disengage. He suggested loosening the skewer and retightening. Is that accurate?

It seems if that were the case:
1. How can I ride 30 minutes or so and all is good.
2. With how finicky the disc brakes are, that if things are not lined up correctly, then the wheel wouldn't rotate at all or be a mess.

Thanks for your help.

I actually have a similar issue with my Zipp 303 NSW disc. From a topic that I started:


Come to think of it, my shifting also seemed to be off before the whole freehub drama started. Could it be a lubrication* thing inside the freehub?






* The oil specified by Zipp seems to be impossible to come by in Europe.

I have a similar issue with my 303 NSW. What did you do to resolve the problem? Does the free hub just need to be replaced or is it a bigger problem?

I’ve sent it back. Awaiting a response now.

I had a similar issue with my 404 NSW. I put in a new cognition disc and it happened again after six months. I sent it back to Zipp after myself and two mechanics were unable to fully solve the issue. Zipp returned my wheel with the explanation that, unless I clean and lube the cognition assembly every six hundred miles with their lube only, it will not work properly.

Have you been able to actually find the oil somewhere?

I don’t think Zipp has been stocking it anymore. Their service instructions also list Phil Wood Bio-Lube as an option for lubing the freehub clutch.

Seems to be close to non existent in Europe as well

I use DumondTech free hub oil in my zipp cognition hubs. Works great. Highly recommend getting a needle applicator (or whatever it's called). I'm not a mechanic, but like to pretend I am.

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Great! They actually have it in The Netherlands: https://www.cxcsupply.com/...x-freehub-olie-59-ml

In the US if you live here:

https://www.coloradocyclist.com/...BbgNyYwaAnx1EALw_wcB

Sorry to hear this. Zipp is a company that produces some of the most expensive wheels on the market and their fancy hubs suck (and have a history of sucking). ...hmmm

They should just spec their rims dt swiss hubs and focus their attention on other aspects of the wheel!

Has anyone been able to solve this?
My NSW 303 stated to lose engagement randomly since last year in April. It started with a loud "click" when beginning to ride and a non smooth sound wile coasting. The click got worse until I could feel it through the pedal. Going through all engagement points produced I found one position where engagement would slip a millimeter or two, but distinctly noticeable.
Then the axial clutch lost engagement completely. This was on and off. I had done regular maintenance to the rear hub, following Zipp's maintenance video to the letter, Phil Wood Bio Lube and SRAM butter included. I then had the wheel at bike shop and they sent it to Zipp (Japan, that's where I´m at). They returned the wheel, telling there is nothing they could do. I contacted the US customer service and they couldn't help either, like wtf.
I have since replaced the axial clutch and the freehub body. Those are expensive spare parts, a bit of metal and a few magnets.
The problem disappear from September to July. Now it´s back.
It looks like the seal isn´t great, water comes in quite fast, so that might be one reason? I wonder if it has something to do with the hub shell, like bad tolerances allowing the clutch to move too much.
Or too high temperatures influencing viscosity of the "Bio Lube"? But that would be ridiculous, right? Imagining riding them in race situations.
When I searched the web I found this thread, as it seemed there are no known issues with the cognition hubs. Those were Zipp`s top of the line wheels and no help from the manufacturer...

I'm popping in here to see if the community has figured anything out? We all know the Zipp hubs have historically been recalled but only after they've been replaced with New Better Improved(tm) hubs... which also get recalled when they are no longer next gen.

I have the Firecrests with hubs that just pull apart with your hands. At least the pawls are captive. Was replacing the cassette the other day and of course the hub pulled apart despite knowing about it and trying to keep it together. The gasket gets knocked off and you got to make sure it is in a proper place before reassembling....

Well, my 2021 Zipp NSW 808 wheel only had about 150 miles on it. 112 of those miles happened at super rain soaked IMTulsa where I rode in super rain probably for about 3-4 hours. The roads were also dirty in some places so plenty of dirt/mud flying around in some short parts. The hub started slipping after that.

I had a similar issue with my HED JET wheels and they provided me with the following instructions. Not sure if any of this helps but figured I would provide in case it does.

Our hub vendor switched to a different grease due to a supply chain shortage without our knowledge. This tackier grease causes the freehub pawls to stay closed instead of snapping open to engage the ratchet ring, giving you reassuring clicks when coasting and forward motion when pedaling. I've included photos of what I suspect you will find.

The quickest solution to get you back on the road is to wipe out the current grease. You will need two 17mm wrenches or adjustable crescent wrenches. The cassette can remain on freehub for this process.

Freehub removal:
Step 1) Remove wheel from frame
Step 2) Locate end caps on hub with flat spots to fit wrenches
Step 3) Turn both wrenches counterclockwise to loosen threaded end cap on rotor side
Step 4) Remove threaded end cap on rotor side
Step 5) Twist freehub body counterclockwise and pull out, the axle will slide out as well
Step 6) Locate tube spacer that is nested in freehub body and set aside for step 8

Wipe out grease from ratchet ring (toothed ring in hub shell as seen in attached photo). Wipe grease off the 4 pawls on freehub body (metal tabs should now spring back when pushed down). Apply thin layer of grease to ratchet ring.

Freehub installation:
Step 7) Slide axle through freehub body
Step 8) Install tube spacer on axle and slide into place within freehub recess
Step 9) Insert axle and freehub into hub shell, twist counterclockwise, press into place
Step 10) Thread end cap onto rotor side axle
Step 11) Use wrenches to snug end cap

The cassette should now only spin freely backwards and should turn the wheel when spun forward. Test this before reinstalling wheel on bike.

It is the "axial clutch" thats proprietary to the Zipp cognition hub that loses engagement. Does the Hed wheel have something similar?

I have the same problem with my 808 NSW. Didi you find a solution to this issue?

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I just sent my wheel back to the bike shop where I purchased and will keep you posted.