Öhlins RFX 38 m.2 Fork: Tech Info, Impressions & Discussion

Cool! Just got one so this is perfect timing. A question I have is for lowers service it says to put damper fluid in the lowers of the damper side. Would motorex 2.5 be appropriate for that? 

I bought one used a few months ago. Been running more psi in the Ramp up than recommended. Love the fork though. Still tinkering a little bit in where to be for the pressures. 

Totally agree with the video saying "a bubble you cannot pop". This fork truly does feel so much better the faster you go. 

I believe the reason damper oil is suggested is the same as fox forks - the damper is auto-bleeding so it can ingest bath oil from the fork leg. The theory is your bath oil could have different qualities that could change the damper performance.

In my research servicing mine, there seemed to be consensus that it’s not a big deal to use normal fork bath oil in both sides, provided you’re probably going to get the damper serviced once a year and it’ll be filled with the proper fluid then anyway. I used Fox Gold in mine and haven’t seen any issues.

On a separate topic, I did remove the negative air spacer from my fork, and BOY did I mangle the main air seal putting the air cartridge back together. I didn’t have a bullet tool, so tried the tape or plastic bag method and failed horribly.

Once I got that fixed, and removed the negative spacer again…I’m not sure I love it. I think the fork was great as is, and though the small bump feel is better, it also rides deeper in the travel, so I had to re-puzzle my air settings. Would love to hear what others think on that though! Overall, incredible fork for rough trails.

Was watching a YT vid of this fork and the guy had removed the spacer and came to the same conclusion that he kind of hated it and it ruined what made the fork so good.

Curious why you needed a bullet tool to put the air cartridge back together. Did you remove the piston from the shaft? My negative spacer had a split and removing it was super easy. Agreed with both of you that the fork does run deeper in it's travel without the negative spacer. I had to increase my air pressures about 15-20 PSI in both chambers to get a similar feel but felt bottom outs during heavy compressions on steeps. My fork is so plush that the difference with or without the spacer is super minimal. This winter I plan on reinstalling the spacer back. 

Other than that, I gave up trying to find the yellow lowers in Canada so decided to paint them myself. Turns out Cub Cadet #2 yellow is a 99.9% match to Ohlins yellow. 

I am pretty happy where I am now but it took some time. I think a lot of people will struggle to get this fork in a good place compared to RS/FOX. I was coming off a ZEB with a RUNT, that fork took some force to clank so I never really experienced it all that often. Diaz also did the alignment thing to it and it was pretty good off the top. Overall that fork worked very well. 

Coming over to the Ohlins it took quite a bit more work to get it into a similar place and I still would like to have Diaz align it. I rode it for a bit and went up and down in pressure then pulled the neg spacer out then sent it to Fluid to change my compression tune. I think whatever they did was the best for me. I was looking to get more hold up without using the spring to do this (I've been wanting this out of all my forks for the last few years). I was really hoping that this fork was going to do this in stock form considering the reviews claim this. I was expecting more of a moto fork feel but in the end it still seems to be a MTB fork. The fluid function tune got me much closer to this but I would ideally still go up 1 or 2 tunes again. They did my rear Ohlins shock and this by far the best shock I've ridden the bump stop feels much better than the stock one. The FF guys know their stuff and talking with them they're also pushing for a similar setup to the moto world. 

176# ready to ride

170mm Travel - Main chamber: 110-115psi // Ramp up chamber: 225psi // HSC: 1(firmest) // LSC: 5 // LSR: 8ish

If you watched the PB video when they rode the DEMO Henry talked about the larger negative chamber on the not factory fork spring. I would really like to try this fork with a larger neg chamber. If someone smarter than me could make one I'd buy one. I used the megneg in the past and really enjoyed what it did to that shock and would be very interested in how it would feel on a fork.

I also experienced this as well but enjoyed how it rode. I ended up bumping up my bar height 10mm

Here are my thoughts on the negative spacer and if I am off on anything please let me know.  

This is from an Ohlins video explaining their air spring for reference, and you can see that the negative spacer only affects the first third of travel. Just as a note on the graph, it is just a screen grab and it might be a little deceptive because the red line is referencing stock negative spring but with an increased ramp up while the green is negative spacer removed but lower ramp up pressure.  As I understood it, removing the negative spacer and increasing ramp up would yield a graph with the green initial curve and red secondary curve. 

Video here: https://www.youtube.com/watch?v=ncztWp_6Uyk

When I first got the fork and didn't know about the negative spacer I was dropping my pressure to get the small bump compliance I wanted.  This would also affect the mid stroke by making it softer as well.  After learning about the negative air spring I took it out based on my experience from owning Vorsprung products and watching their videos.  I had to bump up my pressure from 105 to 115 in the main chamber but this gave me better small bump and the higher pressure gave more mid stroke support as well. 

Long story short, if you take it out I think you will want to increase your main pressure.  For the guys who said it rode too low in travel I would be curious to know what part of the travel you're talking about.  

Thanks for the posting the official information on this. I found mine to be sitting lower in the mid stroke and increase in bottom outs. The fork also bottomed out when riding very steep chutes where the fork is loaded that lead to a big compression. Perhaps I just need to increase the ramp up chamber pressure even more and/or increase the HSC for those trails.

Weight: 165-170 lb HSC: 1 // LSC: 4
w/ Negative spacer: 105PSI/180PSI
wo/ Negative spacer: 115PSI/195PSI

Loving the discussion!

I did have to take the air piston off the shaft, my negative spacer was not split. For me it felt like the dynamic sag after removing the spacer was too much - but sorta my fault anyway, basically have been going back and forth on how much air to add. Will try 10psi more in the main chamber and see.

Edit: @sprungmass I would definitely suggest at least 200 in the ramp for you, I’m 170lbs also and was running 100 main / 220 ramp (no negative spacer) with similar damping to you.

I’m planning on starting with Henry Quinney’s recommendations (basically soft spring to match rebound full open, lots of compression) from his telemetry experiment (apologies for red site reference). I used similar for my previous Fox 38 grip2 going well below recommended air pressure, full closed compression, and full open rebound and I thought it would be kooky and stupid but it was incredible. 

On your 38 did you find that setup had any drawbacks? I’m very curious about it. But I also  enjoy a firmer spring setup that (I would assume) is more willing to leave the ground / gap over stuff.

Shockingly no. I found it very supportive in corners and steep stuff. Thought it might be weird off jumps but same thing, no issue. I think it’s the alchemy of soft spring but compression makes it stable and the fast rebound keeps it supportive and not sloggy. Fwiw I considered myself a firmer spring person too. 

Had the negative spacer taken out by the local service center, solved all my problems with harshness that I had in the beginning. 

Imo it’s not as glued to the ground as my Fox 38 was but more composed when going fast. 

I run more pressure in both the main and the progression chamber than recommended, but for me it’s the best fork I’ve had so far. 

Run both the TTX22 and the fork with HSC on one click from open and haven’t really touched LSC in forever because it just works so well on almost all trails

Well I think my 38 set up is definitely an outlier from what everybody on here is running. 

Main spring: 120-125

Ramp up: 260

Lsc: 8 clicks from closed +/-

Hsc: 1 from closed

Negative spacer removed. 
180mm

I spent a lot of time playing with the set up set at 170mm. Recommended pressures had me running 25-30% sag (I’m 168 lbs soaking wet). Front end felt to low even with 35mm rise bars. So bumped up my pressures to 130 in the main and had the 18-20% sag I’m used to but traction at the beginning of travel not awesome. Rest of the ride was unreal for composure and bigger hit support. 

Took out the negative air spring spacer and traction improved but still room for improvement. Bumped the travel up to 180 and wow, able to drop my pressures by 10-15 psi, traction at the beginning of the stroke is amazing, mid to end stroke support the best out of any for I’ve ridden. 

My last fork was a grip2 36 with Vorsprung Smashpot 45 lb spring. Lsc closed, hsc roughly halfway in the range. I thought that was a decent set up and the 38 poops all over it

Enjoying the thread, so thank you all to are contributing. 

After years on Fox products I switched to Ohlins this year and am loving it. I'm curious how much of this thread would also apply to the DH38, I assume most if not all of it? I'm running a DH38 lowered to 180mm and at park speeds I haven't really noticed the small bump sensitivity needing to have the negative spacer removed. I'm also running a RXF36 on a trail / XC bike and am considering pulling the spacer on that to get some more low trail speed suppleness. Thoughts on that?  

Consider the coil option (pretty sure you can drop it in to the 36 air). I have a 36 coil and it’s so good. The Ö damper is so good w coil

Has anyone tried a half sized negative volume spacer ?

In the fork shootout, was the negative volume spacer in ?

Has anyone pulled the negative spacer and subsequently put it back in ?

Does anyone work on their RXF 38 or any other Ohlins forks? I find that their 50 hour lower service recommendation is pretty important. Having done a couple of 100hr service, I am curious why only the air side ingests so much dirt compared to the damper side. The damper bath oil always looks perfectly clean. I got lazy this year and let it go for 100hrs and the air side oil had an alarming amount of dirt in it. I am pretty meticulous about cleaning the stanchions and wipers after each ride and only ride in dry conditions. The dust wipers are obviously same on both sides. One thing of note would be there is always a decent amount of negative pressure in the lowers on the air side. Maybe that keeps sucking in dirt? Top foam ring (flipped inside out) is from air side and bottom is from damper side. 

This person obviously went way further than 50 hrs and trashed their air cartridge https://www.reddit.com/r/MTB/comments/11zoszk/heart_breaking_bad_news_m…

Other than that I love how I can perform a full service at home with no proprietary tools. Only the damper 200hr service requires a special seal head tool. The 100hr service is pretty straight forward.

Do you re-use the foam rings when you do a 50 hour service or buy the kit with new wipers and rings? Anyone have any luck using Zeb foam rings?

Mid-season I give them a good wash with brake cleaner, flip them inside out and reuse them. This is straight from the Ohlins 50 hour service manual (minus the flipping part). Replace them yearly. Those Zeb bulk ones should be good because the ID is the most important dimension. The Ohlins ones are 1mm taller and 1 or 2 mm thicker OD.

48mm OD
38mm ID
7mm tall
5mm thick
 

Thanks!