Fox 38 air spring in Zeb chassis?

shove this in, think of it as negative tokens, making the fork more linear

https://trutune.co.uk/

https://mrpbike.com/products/noken

I've got one of these in each of my Zebs.  Does what it says.  I can now use ~95% of travel on both my 160 & 170 Zebs, running 1psi over RS suggested pressure.  Feels great.

I don't believe it fits as the 38 air-spring is housed inside a sleeve in the stanchion, so is most likely a smaller diameter than the Zeb air spring. 

They're are quite a few mods/products you can do to make it more linear. But at the end of the day, its still an airspring, so it can only be so linear.

Smashpot conversion (or other coil products) is the only way to make it truly linear. 

Another option:

DSD RUNT, ROCK SHOX ZEB

Second this vote. I've been testing the Noken for a while (review coming shortly) and it works exactly as hoped. It's also really reasonably priced at $70, so it's worth a shot. They have a way to test if it will fit with your frame before you use it, too.

Can confirm, works well in a 170mm 36.

I wonder if you could run both a TruTune and a Noken? 

So a NoTune,... more or less ? 😁

It is possible to fit a Fox Airspring with the sleeve in a Zeb. A german guy has done it, I think he only needed one small part to get the spring fixed in the Zeb Chassis.

It fit suprisingly well, I had some back and forth with him if it would fit, I could ask him what exactly he did and modified to make it happen.

Question to the panel: in your experience, does a 38 have as much built-in progression as a Zeb with the same amount of travel?

I think the Zeb is more progressive for sure. 

God no, 38 the most linear air spring on a fork I've come across. Especially with no tokens and adequate pressure. 

A freshly serviced 38 is eerily close to coil, I've converted every fox fork I've had to a smashpot except the 38.

38 is much less progressive.  The 38 I spent time on I was running 2 tokens on, and I have to run the Noken on the Zeb.

Is it even more coil-like with 0 tokens? I'm running 1 rn and it's still way more progressive than my shock, I'm almost never getting similar travel out of both.

I just put a Smashpot in my 38, but haven't had a chance to try it [-15C + 1m snow at present]. This should be interesting!

0 tokens and 5-10% more pressure than recommended is a good combo I find. My 38 is the first iteration with the Grip2, so less hydraulic support.

The usual mid stroke hammock of airspring is not perceivable with this setup, there is enough ramp up from the airspring itself to avoid bottom outs with my 180mm airspring.

It doesn't have that stictionless feeling for the first 5-10mm of travel like a coil, but as I said, freshly serviced it's pretty close. Worth a try, if you don't like it go back to your previous setup. Cost nothing.

I do find that the 38 air spring is pretty happy in a ton of configurations, all of them rideable. No tokens with higher pressures work super well, but so does more sag and adding in tokens. I've run anywhere between 118 PSI to 96 PSI and fond that I can make something work well in all those configurations. It's actually kind of annoying since I waffle with my air spring more than I ought to. Though I do have to admin that 5-10% more pressure sounds like a lot. I usually run mine (in 170mm) with a touch less, or equal to, stock and maybe a token or two. Though I did run 87% of recommended pressure with a super quick rebound and found it pretty fantastic on some styles of trails. 

As for adding things like the Seccus to the 38. I really never jived with the Seccus. I felt like if I ran the 20% higher pressures that it liked I would just hit a wall about 2/3 through the travel, and if I ran lower pressures I didn't really get any benefit vs just playing with the stock spring and tokens. 

My experience with RUNTs and Rockshox air springs is that the RUNT will absolutely make the beginning and midstroke more linear (i.e., mid stroke support), but also make the end of the stroke really progressive. Didn't work for me.  Also, my understanding of the Diaz damper tweaks for the RUNT is that he was reducing compression damping.  

Regardless, Diaz and the RUNT are great.  Contact them and they'll give you a much more informed opinion than me.  Great to deal with and highly recommend.

+1 on the TruTune if you're looking to reduce end stroke progression.  I also think I can feel it in a good way on rebound, but so hard to know if you're feeling what you want to feel or think you should feel on things that nuanced.  On a Lyrik at 160 (closer the fork is set up to it's max travel, the more progressive it is), I've added an MRP Lift and TruTune and really like it.  Damping feels like it holds the fork up high enough and TruTune unlocks the stroke to about 90% unless I really f' something up.

Maybe if the Lyrik was set up at 140 I'd like the RUNT, but I've also tried a RUNT in a 170 Zeb and came to the same conclusion.  

Can't think about this stuff without getting mad all over again that Spesh killed the MI System 2.  That thing was gonna unlock a lot of secrets for riders without access to pro-level data systems.

Biggest mistake was replacing my Fox Factory 38 with the Zeb Ultimate 3.0

Just recently upgraded to the 3.1 piston, lighter compression tune and fast rebound. Hopefully I can get it to feel decent.

Did the same mistake with a Fox 36 Performance Elite to Lyrik Ultimate Charger 3.0. The Charger 3 damper is god awful in my opinion. No experience of the 3.1 though. 

I'll preface by saying that my preferred ride feel is more similar to ohlins and manitou.

For the noken on a Zeb 180 w/lift damper, I found that the stock cap was too progressive and that the noken takes too much out of the midstroke for my preference. I think if there was a noken .5 product, that might suit me better.

I can see why a lot of riders may like the Zeb 180 noken lift combo and I find it less fatiguing to ride than a fox38 grip2 at 180 and 170. I.e. if someone likes the ride feel of rockshox, I would say that the noken lift combo on the zeb is certainly an improvement. 

Would love to try an F38 airspring in a zeb chassis with lift damper 

I forget whether the Noken still has threads inside it to screw on a token - if it does, you could easily saw a stock token in half and add that back on to get effectively -0.5 tokens.  Or add the equivalent oil volume of 0.5 tokens to the positive chamber.  I ended up adding 1 psi to each of my forks running them to bring back a little more mid-stroke support - but again, I'm still able to use a lot more travel, a lot more of the time.

I believe this guy actually engineered a similar air spring as the Fox38 to be used in other forks, maybe try this one out before you try to modify a fox spring to fit a zeb fork.

https://www.instagram.com/rgtec_bike_components

Luft Fusion air spring for Fox and Rockshox forks | eBay

No threads on the Noken to add tokens on. We considered that, but adding the feature reduced volume and added manufacturing complexity. The tradeoffs, we decided, weren't worth it.

With the two generations of Rock Shox air springs available, volume tunability with the standard air cap, and the Noken, there are a lot of different spring curve options with various combinations.

+1 on the Lift in an older Zeb chassis.  Like it a lot.

Could try the Noken with a Neopos and a little more air in the spring.  Have used Neopos in Rockshox and liked them.  Formula says not compatible, but been fine for me.  Plus, I don't feel like a bike is really "mine" until I've done at least one thing a manufacturer doesn't recommend.

That Noken wouldn't that be a potential to damage a frame a lot?