Öhlins RXF36 Fork

If you follow the racing scene, you've no doubt seen the Öhlins RXF 36 under some of the world's fastest EWS racers. It will soon be available in a new wheel size and is the company's first publicly released 27.5 model. Just like the well-regarded RXF 34, this bad boy sports a three chamber air spring and multiple external adjustments that allow you to really dial in your ride. What else is new? Let's dig in.

Highlights

• 140-170mm (5.5-6.7 inches) travel options
• 27.5-inch specific design
• 36mm diameter stanchion tubes
• Tunable three chamber air spring system: two positive, one negative
• TTX twin-tube damping technology with 22mm piston plus parallel and separated oil flow
• External low-speed rebound adjustment
• External high and low-speed compression adjustments with pedal platform on high-speed lever
• Two-piece crown with tapered steerer tube
• Low friction seals and bushings
• Fits up to 2.8-inch tires
• 180mm direct mount disk brake
• 46mm offset
• Boost 15x110mm axle
• MSRP: $1,100 USD
• Available July 2017

Chassis Updates

Larger 36mm stanchions are only part of the story as the fork's chassis has seen a number of refinements. First up is a more traditional two-piece crown. Recognizing that the unique uni-crown design used on the RXF 34 and 29-inch RXF 36 had some limitations in terms of frame and headset compatibility (Chris King, for example), Öhlins chose to make the new RXF 36 27.5 compatible with a standard headset race. Not only does this simplify things and reduce cost, but Öhlins claim they were able to achieve the stiffness and ride feel they were after with the two-piece system.

Keeping up with the latest trends in the tire game is no easy task, which is why Öhlins made this new fork compatible with up to 27.5x2.8-inch tires. That's a major improvement over their other forks. Not running some massive meats? It's all good, you'll enjoy added mud clearance when conditions get nasty.

The fork sports a Boost 15x110mm axle that secures the front wheel in a similar "floating" fashion to motocross bikes. Öhlins ensures that the fork works as freely as possible by holding the wheel in place without forcing the fork legs together, reducing friction.

You'll find three threaded holes on the back of the arch that serve as mounts for a soon to be released mud fender. The fork has a 46mm offset, keeping things very agile at the bars.

TTX Damping Technology

Another big highlight is the twin-tube (TTX) damper design. The damper is essentially the same as their RXF 34 with a couple of small revisions as a result of their work with the Specialized Enduro and Gravity teams, including a few seal updates. As the fork moves, oil flows both inside and outside of the inner tube, making use of the stanchion wall as the outer tube. This layout is said to control oil pressure levels better than the standard single-tube damper, which in turn means more controlled, consistent damping. Öhlins says this "ensures initial smoothness while staying high in the travel with excellent bump absorption, traction, and stability."

Both low and high-speed compression are externally adjustable and fully independent, with 15 and 5 clicks of adjustment respectively. There are also 15 clicks of low-speed rebound adjustment. This provides the same overall damping range as their other forks, but the slightly reduced click count makes set up easier. "It was difficult for some customers to feel the difference with one click," Öhlins told Vital, "so we made each click a real world feeling." The fork is said to "provide a tuning range that will allow every user to find an optimal setup for the terrain at hand, without getting lost in the process."

Low-speed compression adjustments are controlled by a bleed needle. Faster hits direct oil through the shim stack, and adjusting the high-speed compression knob puts pressure on the shim stack to increase the damping force. The platform-style pedal mode is easily activated by flipping the high-speed compression lever all the way on, resulting in a very firm feel that will please pedal smashers. All knobs are easy to turn with or without gloves, providing a nice audible "click" with detents you can feel.

I’m a huge fan of the way it feels on both small bump sensitivity as well as how supportive it is on bigger jumps, in berms, and on rough trails in general. – Walker Shaw

Öhlins' experience shows through big time when it comes to the damper's performance. Much like their rear shocks, the entire range of compression damping is usable and puts you in a good spot. Each adjustment makes a small but consistent damping change.

Custom tunes are available for the lightest and most aggressive heavy riders. Öhlins says you aren’t far from product or professional back up thanks to a recent increase in the number of sales outlets and service centers globally.

Three Chamber Air Spring

Depending on the negative spring configuration, air-sprung mountain bike forks typically have one or two air chambers. The RXF has three air chambers - two positive and one negative - contained within a standalone air spring cartridge. Both positive chambers can be adjusted with a shock pump at the top and bottom of the fork.

Like other forks, the main chamber controls how easily the fork compresses at the beginning of the stroke and provides mid-stroke support. The "Top Out" chamber (negative) works like a top out spring and is self-balancing, providing an ideal ride no matter the pressure in either of the other two chambers. What's unique to Öhlins forks is the "Ramp Up" chamber, which controls the spring rate at the end of the stroke.

Much like the volume spacers used in other forks, the ramp chamber is designed to give extra bottom-out support by occupying space inside the air spring. The Öhlins design is far more convenient than typical volume spacer, however, because it's externally adjustable and doesn't require you to open the fork or have spacers on hand.

It's easiest to think of the ramp chamber as a small, high-pressure air spring inside of a larger, lower pressure main air spring. As the fork is compressed, the air pressure inside the main spring rises, pushing against the ramp piston. Unlike volume spacers, the volume occupied by the ramp chamber shrinks. Adding more pressure to the ramp chamber makes it shrink less at full travel, taking up more volume and creating a more progressive spring curve. We noted that the pressure recommendations have been improved with added ramp up values, giving the fork additional bottom-out support at the factory suggested settings.

The separate main air chamber and ramp up air chamber is so cool to really fine tune the fork, something that no other fork does. – Curtis Keene

All of this allows you to change the shape of the spring curve, customizing how the suspension reacts to the terrain. Want a more supple feeling fork that still has lots of bottom-out support? Can do. Simply drop the main air spring pressure a bit and add some to the ramp chamber. This system has the possibility of acting much like a coil spring, which is perhaps its biggest advantage over a traditional air spring design.

New for the RXF 36, travel changes only require a new air spring and not a new damper shaft. The other designs had shortened damper shafts on forks shorter than 150mm which Öhlins felt was expensive.

In Action

Join Vital for a test lap on some rocky trails in Durango, Colorado:

Visit www.ohlins.com for more details. The new RXF 36 37.5 will be available starting July 2017. It's accompanied by a new RXF 36 Coil fork that we'll be reviewing in the coming months and lighter weight coil springs for Öhlins rear shocks.

About The Tester

Brandon Turman - Age: 31 // Years Riding MTB: 16 // Height: 5'10" (1.78m) // Weight: 175-pounds (79.4kg)

"My current riding joys include pulling up hard and hucking test bikes into poor landings and techy sections with reckless abandon, then seeing how they react upon landing." Formerly a Mechanical Engineer and Pro downhill racer, Brandon brings a unique perspective to the testing game as Vital MTB's resident product guy. He has on-trail familiarity with nearly every new innovation in our sport from the past several years and a really good feel for what’s what.