Öhlins RXF38 Review

by Tor Weiland August 17, 2023

ohlins RXF38 Fork laying on concrete floor

Intro

Today, we’re diving into the world of Swedish suspension, and are looking into the RXF38 m.2 from Öhlins. I figured they’d be too busy with their meatballs and producing ABBA songs to design mountain bike suspension, but Öhlins has made something special with their RXF38 m.2. Let’s take a look inside this fork, ride the heck out of it, and help you figure out if this is the right fork for you!

Riders demand a lot from single crown forks these days. We need them to put up with endless abuse in the bike park with days full of braking bumps and flat landings, but also need to fine tune the damper for maximum traction on the race track. The RXF38 is Öhlins' 38mm stanchion enduro fork that’s built for exactly that. Öhlins may be a bit of a third party in the mountain bike suspension space, but they’re world renowned for their car and motorcycle suspension. Öhlins has been at the pointy end of suspension tech and performance since the 70’s, before mountain bike suspension was even a twinkle in its father’s eye. And now the second iteration of their RXF38 is bringing that suspension experience to the long travel enduro world, with all the features you can expect in a high end fork and performance that rivals the Fox 38 and RockShox ZEB. First, we’ll be checking out all of the features of this fork, then get it all set up, and finally talk about how it feels on the trail!

Öhlins has made something special with their RXF38 m.2

Öhlins RXF38

TTX18 Damper with High Speed Compression, Low Speed Compression, and Rebound adjustments
Three chamber airspring that uses ramp up chamber to tune progression
Floating axle keeps stanchions and lowers parallel for minimal friction
Amazingly smooth fork that is perfect for racing or riding rough trails
38mm stanchions provide fantastic stability in rough terrain

Inside the Öhlins RXF38

The RXF38 m.2 is the second generation of Öhlins' long travel enduro fork platform, and is the most capable single crown fork in their lineup. Sharing similar technologies with the RXF36, the RXF38 uses the TTX18 damper and three chamber air spring packed in its 38mm stanchions. This fork weighs in at 2320 grams (50 grams less than a ZEB and 110 less than a Fox 38), comes in either 160, 170, or 180 mil of travel, uses either 44 or 51mm of offset, and is 29 inch only! For the dedicated 27.5 fans out there, you could still run a 27.5 front wheel but you’ll have a longer axle to crown measurement than on a dedicated 27.5 fork with the same travel. It’s got blue SKF seals, a 200mm post mount for your front brake, and your typical 15x110 boost spacing.

Öhlins uses a purpose built chassis for the RXF38 that’s designed for 38 mm stanchions just like their dual crown downhill fork, the DH38. On the inside, these two forks have the same damper and a similar air spring and it’s great to see similar technologies across different platforms to keep their catalogs more streamlined.

Removing the air spring is incredibly easy on the RXF38, and you don’t even need to drop the lower legs for a travel change or to service the air spring! This is possible because the Öhlins air spring is an entirely contained cartridge that you can pop in and pop out from the top of the fork, while most other forks use the inner walls of the stanchion as a part of the air spring assembly, which means you have to drop the lower legs to get the air spring out. Just use a cassette tool on top of the RXF38 and a socket on the bottom and you just removed your air spring faster than figuring out how to pronounce Öhlins.

Öhlins Three Chamber Air Spring

Two positive air chambers and one negative
Ramp up chamber allows riders to fine tune fork progression
Possible to adjust not only how progressive the fork is, but also where in the stroke progression is found
Easy removal without dropping lowers to make servicing and changing travel very straightforward

Öhlins air springs use a three chamber air system as opposed to the typical two chamber positive and negative system found in Fox and RockShox forks. In addition to the same positive and negative air chambers, the third chamber is their ramp up chamber, which is another positive chamber, and uses a second valve on the bottom of the fork that you’ll inflate with a typical shock pump, just like the top valve.

While these three chambers achieve the same goal of tuning your airspring just like the two chamber system, it’s accomplished very differently. In a traditional two chamber system, reducing your positive volume using volume spacers gives your fork a more progressive leverage curve, and removing them makes your fork more linear. By the laws of physics, compressing a smaller volume the same amount as a bigger volume is going to take more force, resulting in a really simple and easy to understand way to add progression.

Now enter the three chamber system, which turns that on its head, using a secondary positive chamber that controls the progression of the fork instead of volume spacers. As the RXF38 compresses, the main positive chamber gets compressed, which increases its pressure. That pressure increases until it reaches the same pressure in the ramp up chamber, and then, once they’re the same pressure, a piston between the main chamber and ramp up chamber opens to combine their volumes, effectively increasing the volume of the main positive chamber to also include the ramp up chamber volume. So for example, with 100 psi in the main chamber and 200 in the ramp up, the fork compresses and the pressure in the main chamber builds until it reaches 200 psi. Then the piston opens to add the ramp up chamber volume into the main chamber volume. Now we still have 200 psi in both chambers, and as we continue to compress the fork, they increase in pressure in unison. Now that your volume has increased, your fork is actually more linear than it was before the volumes joined together because we’re compressing a greater volume of air.

ohlins RXF38 Air Spring disassembled to show positive and negative chambers

Inside of the three chamber air spring - that yellow piston head drives the main chamber, with the blue cylinder housing the negative air chamber.

By adding or subtracting air from the main chamber or the ramp up chamber, riders can tune where exactly the progressive stroke of the fork ends, and how progressive the leverage curve is. By adding air to the ramp up chamber, its volume is added to the main chamber later in the fork stroke, and the smaller volume is compressed for longer, giving you a more progressive leverage curve. By adding pressure to the main chamber but leaving the ramp up chamber pressure the same, the fork will become stiffer in its initial stroke and less progressive later in the stroke because the main chamber pressure will equal the ramp up chamber pressure earlier in the stroke, increasing the total volume earlier and reducing total progressivity.

All of this is a pretty complicated way to say that by adding pressure to the ramp up chamber, the RXF38 becomes more progressive and resists bottom out, while removing air from the ramp up chamber makes the fork more linear and allows riders to use full travel more often. The main benefit riders will get from this three chamber system is tuneability, with the option to change where the progression in the fork is and how progressive it the leverage curve is through infinitely adjusting psi rather than being restricted to volume spacers.

Öhlins has a great video that helps visualize exactly what’s happening inside the RXF38 as it moves through its travel. Their graph of the leverage ratio through the forks travel does a great job of visualizing exactly how to fine tune your RXF38’s air spring to get the exact support you’re looking for. About halfway through the graph, you can actually see the point where the pressure of the main chamber and the pressure of the ramp up chamber equalize and begin sharing volume because the curve becomes more linear at that point.

Öhlins TTX18 Damper

3 clicks of High Speed Compression
15 clicks of Low Speed Compression
15 clicks of Low Speed Rebound
Heavily damped feeling that feels best when ridden hard

Right next door in the other fork leg is the TTX18 damper. With some pretty standard features on the outside, it’s easy to assume that this damper isn’t anything to write home about, but in the riding review, we’ll explain why that just isn’t the case. On top, you’ve got Low and High speed compression knobs with 15 and 3 clicks respectively, and a rebound knob on the bottom with 15 clicks. The high speed compression knob is a lever style that’s easy to adjust on the trail and see exactly which click you’re on, while the low speed compression and rebound knobs are just your standard knobs that require manually counting each click to figure out how many clicks you have.

Between those two legs is the floating axle, which keeps your lowers parallel with your uppers and reduces friction in the whole system. Standard thru axles can be prone to slightly “pinching” the lower legs together if the hub isn’t machined 100% perfectly, and floating axles do a great job of reducing friction in the system. Notably missing from the RXF38 chassis is any kind of air bleeders like what’s found on the Fox 38 or RockShox Zeb. This definitely isn’t a deal breaker, because obviously we rode bikes for a lot of years before these bleeders came out, but if you spend a lot of time in the bike park and your rides have huge changes in elevation, then you might miss this feature.

Setting up the RXF38

Right on the lower legs of the fork, Öhlins provides some initial air pressure numbers for the main chamber and ramp up chamber, which is super helpful because I had no clue where to even start with ramp up chamber pressure. For my weight, they recommended about 100 psi in the main chamber and 200 psi in the ramp up chamber. Their general rule of thumb is to have twice as much psi in the ramp up chamber, and you need to make sure to inflate your ramp up chamber before your main chamber. After riding the fork a bit and bottoming out way more often than I’d like, these recommended settings were way softer than I needed, and I ended up at 110 and 250 psi for my 180 lbs riding weight.

Adding or removing pressure from ohlins rxf 38 ramp up chamber

Let’s look at the TTX18 damper now. It didn’t come with any recommended settings or anywhere to start, so I was left to fend for myself to figure out how to set up this damper. To start with, I just set everything in the middle of its clicks and hit the trail. I spent a few rides spinning the dials to their fully open and fully closed settings, and found that for the most part, there was plenty of adjustment in either direction for me to find a comfortable setup with clicks to spare.

With just three clicks in the High Speed Compression circuit, I found that adding any High speed damping really compromised the sensitivity of the fork through small to midsize compressions, and I really struggle to see any situation where I would want to run any clicks of high speed on the RXF38. The other two adjustments, low speed compression and rebound, offered a great range of adjustments that I clicked through depending on the trail or riding conditions, but for typical summertime trail riding in town I settled on 6 clicks of Low Speed Compression and 7 clicks of Low Speed Rebound. And both of those are measured from closed!

Riding the RXF38

Right from the first ride with this fork, I could tell that it wanted to be ridden FAST. Faster than any other fork I’ve ridden. It made every ride feel like I was racing the clock and it really wanted to be pushed to the limit and held there more than any other fork I’ve ever tried. The heavy damping of the TTX18 damper helped keep the fork composed and predictable through compressions, and definitely increased my confidence through chunky terrain.

mountain biker riding through bellingham woods on chromag full suspension bike with ohlins fork

The stiffness of this chassis was exactly what I was looking for with a 38 mm stanchion fork, and it held its line through rough sections of trail notably better than its little brother, the RXF36. After riding the RXF36 for a while last year, my only complaint about how that fork rode was that it just couldn’t hold its own through the chunk like the 38mm forks I’d gotten used to, and was more prone to binding during big compressions that would torque the fork. The plowability of the RXF38 chassis solves those issues entirely, and is definitely happiest when you’re pointing it into bomb holes or letting off the brakes through a rock garden. But I also never felt like the chassis was too stiff to the point of rattling my hands off the bars, and Öhlins definitely struck a nice middle ground between their DH38 and RXF36 forks in terms of comfortable stiffness.

While I typically prefer a fork that is less damped, which is why I prefer the RockShox Zeb over the Fox 38, I’m surprised to say that I really enjoyed the heavily damped feeling of this RXF38. I think that I’m able to like the damped feeling because the TTX18 damper feels noticeably smoother than other dampers. It’s definitely hard to explain without having you physically ride the fork, but the action of this fork is just incredibly smooth, just like the RXF36, and I think that’s a result of a very high quality damper that does its job fantastically without feeling harsh. This definitely changed how I set up the fork compared to my ZEB, and I found myself relying more on the low speed compression than the air spring to hold me up in the travel than other forks. The RXF38 did a great job of staying high in its travel and staying away from the super progressive end stroke. This was most noticeable through repeated small compressions like riding over root balls or chattery braking bumps where you don’t want to be using all of your travel. Plus, staying high in the travel lets your bike keep its slack head angle and long wheel base.

There’s a lot to like about how this fork rides, and I only had a couple complaints. The first one is pretty vain, but after riding the dead silent ZEB for a few months, the small amount of noise this fork makes was kind of a bummer. That’s not to say that this fork is an absolute racket, and the noise level is super comparable to the Fox 38, but after getting used to that silent Zeb it’s tough to go back!

The only other issue I had we were actually able to solve! And it comes down to a little negative volume spacer that comes installed in the fork. During the first few rides, the RXF felt harsher off the top than the Fox 38 and RockShox Zeb, but after talking to Öhlins and taking their recommendation of removing this little spacer, the RXF38 gained some amazing off the top suppleness that put it right in line with the other big boys. This volume spacer sits inside of your negative air spring, and a larger volume air spring helps pulls your fork into its travel during compressions and helps overcome any stiction in the system to make things buttery smooth. Honestly, I’m really not sure why this fork is shipped with the spacer installed because it feels so much better without it, but luckily removing it is super easy and just takes a few minutes.

Conclusion

Not many mountain bike components are purpose built for racing, but the Öhlins RXF38 fork is exactly that. With the unbelievably smooth and confidence inspiring damping provided by the TTX18 damper, this fork is happiest when being piloted with pure speed in mind. That’s not to say it can’t be appreciated at lower speeds as well, and the impeccable small bump sensitivity puts a smile on the face of anyone lucky enough to strap this to the front of their bike. As long as you're willing to learn a new setup procedure for the three chamber air spring, riders can expect fantastic performance from the Öhlins RXF38.

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ABOUT THE RIDER/WRITER

NAME	AGE	HEIGHT	LOCATION
Tor Weiland	24	5'11"	Bellingham, WA

Current Bikes: Chromag Lowdown

Bike Size: Medium/Large

Favorite Trails: Oriental Express, Galbraith

About Me: Hailing from the sunny landscape of California, Tor headed north and landed here in the cloudy town of Bellingham, WA. His riding style is "PINNED" and he loves to scope out those seemingly impossible triples. He loves riding and also loves sharing his experiences with others. You can catch Tor in front of the camera or behind the keyboard, but best of luck catching him on the trail!