First Ride: RockShox RS-1 inverted fork

29er Forks Sea Otter Classic

We got a ride on the new RockShox RS-1 inverted fork at the Sea Otter Classic last week and came away pretty impressed by its smoothness, suppleness and responsive steering. Much of its performance success can be attributed to its so-called “upside-down” design. Though inverted forks have many advantages and are commonplace in the motorcycle world, widespread success has eluded the design in the bike market to date. RockShox hopes to change that with its new RS-1 29er cross-country superfork.

Why go inverted?

The advantages of an upside-down fork include a stronger, stiffer upper which produces better steering and reduces flex. The sliders are also closer to the ground so there is less leverage, friction and wear on the seals during use. With gravity constantly feeding oil to the seals, they remain lubricated which adds to the fork’s smooth operation. Though less dramatically than on a motorcycle, the inverted design produces less unsprung weight with only the sliders and axle going up and down instead of the whole fork leg. This makes the fork more supple and reactive to bumps.

What’s made the inverted design such a challenge for bicycles is balancing the amount of material weight necessary against torsional stiffness requirements. Since there is no fork arch holding the two legs together, independent leg movement has been an issue in past efforts, and forks tended to be flexy and not steer well. To compensate, manufacturers tried adding material and increasing diameters, but were left with forks too heavy to be viable.

Technology to the rescue

RockShox has had an inverted fork on the drawing board for several years now and only recently has their technology advanced to the point of making the design a reality. The first technology is carbon fiber and the processes RockShox has developed to create a one-piece fork upper, steerer tube, and crown. With its Formula 1-like lines, the RS-1’s upper molding is a sight to behold, and in your hand it’s equally impressive to feel—stiff and strong, yet feather-light.

The other key innovation is what RockShox calls Predictive Steering technology—a hub and axle system that locks the independent legs in place and compensates for the lack of an arch. A massive 27mm axle called the Torque Tube runs through the proprietary hub and connects the two 32mm stanchions to create a stout, stiff brace that holds it all together. A 15-millimeter Maxle Ultimate thru-axle is used to press the fork dropouts against the knurled ends of the Torque Tube making a connection that’s massively stiff and budge-proof.

New internals

With the flex issue solved, RockShox turned their attentions to the fork’s internals and created the new Accelerator Damper. The circuit keeps air and oil completely separate for more consistent performance, while the remote-only lockout uses a floating-piston design that compresses the oil when activated resulting in a firmer lockout—an advantage in racing situations like sprints and climbs where power transfer is key. The remote is an XLock hydraulic unit like those used for the Reverb dropper post, and there’s an XLock Full Sprint version that actuates the RS-1 and a compatible rear shock simultaneously.

The damper also includes RockShox’s Dig Valve compression circuit which was created to manage fork dive during successive hits and heavy braking. It also features their Rapid Recovery system to keep the fork riding high, in the plushest part of the travel. Finally, RockShox ported over its Bottomless Token air-volume spacer system from the Pike to adjust how progressive the fork is through its travel.

How costs what?!

With advanced carbon construction, mold-breaking design and souped-up internal goodies, you knew the RS-1 wasn’t gonna be cheap—and at a whopping $1865 it’s more than twice the price of a SID XX. On top of that you need a Torque Tube-compatible front wheel or hub, of which there’s only SRAM’s and a rumored DT-Swiss option. In either case, you’re looking at another grand to get it sorted.

Who is this fork for?

By its nature, the RS-1 is very exclusive and suited only to world-class cross-country athletes. It’s a bit like the Formula 1 auto racing paradigm. We revel in the fact that they develop new technologies to win races even though few of us can afford it. Down the road, we hope the technology proves out, economies-of-scale kick in and we can buy the mere mortals version eventually.

The test ride

We took the RS-1 for a spin on the grassy hills of the Sea Otter XC course and it is indeed an eye-opener. Installed on a 100mm-travel Trek Superfly, the fork felt supple and steered incredibly well. It silenced the braking bumps and chatter of the course’s high-speed downhills and was so lively it invited constant jumping and flicking.

Mated with the new RockShox Monarch Debonair rear shock, the bike felt like it had more travel than it did. In fact, when I mistakenly commented that this “Trek Fuel 29” felt more supple than the one I had at home, a SRAM engineer pointed out that I was not on a Fuel, but a Superfly with 20mm less travel.

The damper is indeed a revelation. With stiction minimized, it enters its travel very smoothly with no abrupt resistance, which translates to a very supple experience. Coupled with fast, responsive shock absorption at the upper part of the travel, plus excellent mid-stroke support and we have an unprecedented XC fork in our midst. The rear Debonair shock has a very similar characteristic where it is very supple in its sagged position. But as it tops out, there is no harsh part in its initial travel that is common to other rear shocks.

Bottom line

Given the advancements, would I buy this fork at $1865 plus the new wheel required for the axle standard? No—it’s too much money for my non-podium abilities and aspirations. But I relish the fact that it’s a better XC racing fork, and that very smart folks are bringing it to market to push the performance envelope. I also appreciate that what’s at the bleeding edge today may be commonplace tomorrow. So while it’s not for me—or probably you—now, someday some version of it might be.

YouTube Preview Image
RockShox RS-1 Details
  • Wheel Size: 29-inches
  • Travel (mm): 80/100/120mm
  • Stanchions: 32mm aluminum, Fast Black
  • Steerer: Tapered Carbon
  • Offset: 46 and 51mm
  • Axle: Predictive Steering – Torque Tube w/Maxle Ultimate
  • Damper: Accelerator
  • Damper Adjust: XLoc Remote (Sprint or Full Sprint)
  • Spring: Solo Air
  • Colors: Black, Diffusion Black
  • Decal Color: Red/White, Silver
  • Weight: 1,666g (3.67lbs)
  • MSRP: $1,865

For more information visit RockShox.com.

First Ride: RockShox RS-1 inverted fork Gallery
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Riding the RS-1 at Sea Otter Course.

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RockShox RS-1 at Sea Otter course

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RockShox RS-1 at Sea Otter course

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RockShox RS-1 cornering at Sea Otter course

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RockShox RS-1 Close-up

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RockShox Monarch RT3 DebonAir

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RockShox RS-1 front view

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RockShox RS-1 on Trek Superfly

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RockShox RS-1 on Felt Edict Nine FRD

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RockShox RS-1 on Felt Edict Nine FRD - front view

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RockShox RS- 1 Torque Tube

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RockShox RS-1 Top View

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RockShox RS-1 Bottom

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FS RS1 29 SA 120 DFBLK Bottom

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FS RS1 29 SA 120 Black Top

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SRAM MTB Rise XX PS Hub Axle

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About the author: Francis Cebedo

The founder of mtbr and roadbikereview, Francis Cebedo believes that every cyclist has a lot to teach and a lot to learn. "Our websites are communal hubs for sharing cycling experiences, trading adventure stories, and passing along product information and opinions." Francis' favorite bike is the last bike he rode, whether it's a dirt jumper, singlespeed, trail bike, lugged commuter or ultralight carbon road steed. Indeed, Francis loves cycling in all its forms and is happiest when infecting others with that same passion. Francis also believes that IPA will save America.


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  • MsC says:

    So, how do they protect the lower fork legs from rock impacts? A chip in the coating and this will easily rip the seals. A shield like on Cannondale’s Lefty?

    • Pachinko Johnson says:

      This is for roadie XC racers who seek out “MTB” races that are 98% fireroads so they can their “MTB” friends they can kill on mountain races. Since they’re all asphalt, there aren’t any rocks to worry about.

  • Rusty Shakleford says:

    The solutions being used to offer an invert fork (left sided only, teardrop shaped legs, super stiff hub, etc) are always going to be awkward especially if the fork is intended for XC. Each come with their own obstacles. Lefty has an advantage due to it being around for awhile and through several iterations (some were great, some weren’t) and having wide spead 3rd party support for the fork’s obstacles (hub manufacturers, steerer tube adapters).

    RS-1 also has an advantage in that c-dale is not really a susp company. RS-1 advances, trickle downs, and componentry might happen faster.

    It seems for now, lefty is the only other widely used invert fork intended for XC, so the comparisons will continue I guess.

  • Ryan B says:

    Many of these advantages have been realized by Cannondale Lefty riders for years. I am concerned (as I am with my lefty) with the vulnerability of an exposed stanchion tube(s) so close to the trail. Not a big deal for many but if you ride technical trails one wrong move could cost you. Also, for the money I would expect it to be lighter. The carbon lefty 29er weighs in at just under 3 pounds and costs over $400 less. I’d also bet that the Lefty front hub is among the lightest in the industry. That said, it looks really sweet and I’m excited that other companies are doing something different outside of enlarging stanchion tubes and “dampening for dummies” (see Fox Terralogic).

  • Late to the party rockshox says:

    I agree with many comments above. This is pretty much a Lefty wannabe but with a bigger price tag and more weight. Cannondale may not be a suspension company, but they’ve totally nailed it with the Lefty.

  • Jeff says:

    Who is this for? Dentists.

  • Matt says:

    Even if inverted forks are better – all I could think is: “Every now and then – I crash. And when that happens the part of the fork that invariably loses some paint and or aluminum is the lower part of the fork.” I’d rather lose some paint than scratch up my stanchions anyway. Especially if all the fluids are now pointing downward toward the seals in the inverted fork.

  • David says:

    So ……, why were the designers unable to build this inverted fork with an arch, or bridge, of some kind between the two legs?

  • Rob says:

    On a traditional fork the arch moves up and down with the lower body. To add an arch it would have to be connected tot the axle and would be in the way and so long that it would flex.

  • phiilp says:

    All I can say is that this was done back in 2003(ish) with the marzocchi RAC air….. used most of the same technology too. i feel like one of the few people who remember this fork, also come to think of it there was a manitou supernova which was a similar concept…….
    good on rockshox though

  • Why Not says:

    I see lots of skepticism and maybe it’s justified, but why not have a fork like this? Obviously money has been spent on development and the fork is expensive with few people willing to throw money at it (or crash it) – I say just see how it goes and if it’s bigger than just trying to shake things up and something good comes out of it, maybe we can all enjoy the technology some day. Actually, I’d be curious how riding just a ‘normal’ carbon fork vs this one compares.

  • SpinM says:

    As many of the other commenters already pointed out, this fork just invites to be compared to the Lefty, even more so, because the latest Lefties include RS internals.

    So, this one has one crown less, one tube more, weights more, costs more and doesn’t come with any protection. Hmm… even so, I applaud the openmindednes of RS going this way.

    By the way – where do you put the speed sensor for your cycle computer?

    • Greg says:

      The only Rockshox internals in leftys that I’m aware of are the solo air piston and the x-loc assembly. The critical part of it, the damper, is all Cannondale.

  • Lars says:

    I for one am green with envy that I didn’t get a leg over one like FC did… Who cares that others have tried and failed, or that a bike company has a one-legged version? We are talking about RS here, as in the largest fork manufacture based in the US, which I think is effing cool. Did anybody catch all the development done in the dampers? Wouldn’t we all like to see some of that in other forks?

    My guess is there are some factory SRAM XC racers who will be stoked to race on one, and thousands of NICA kids drooling….

    Plus, this fork is sexy as hell…

  • RustyS says:

    Interesting, and probably much like USD forks on motocross bikes – completely unnecessary and like USD forks on motocross bikes will probably take 10 or more years to actually work better than the conventional fork in ‘real world’ circumstances.

  • coop says:

    X Fusion is also offering a USD fork this year with a similar price tag.

  • mark says:

    Maverick DUC32 anyone? You can pick up a used one for WAY cheaper than $1800, and it’s silly light. Mavericks’s 24mm thru axle and proprietary hub is awful similar to this new 27mm version. Also, the Maverick has mount points for plastic guards (MX style) that shield the exposed stanchions from scratches. I have owned this fork for years, with numerous unplanned offs, and have yet to get a scratch.

  • jim says:

    I applaud them for investigating different designs. However, like most other things in the MTB world, they are seemingly designed without reference to the trail and tranportation hazards of everday use (bedded in rocks and stones flicked up by your or the guy in front’s bike, other bikes in the back of a van scraping them etc.) When you transport this thing with the front wheel off….then that stanchion is *really* exposed and you really don’t want scratches on inverted stanchions.

    One upside of this design is that the stanchions are now, once again, (as they were when we had stanchions that bolted into crowns!) individually replaceable!! I’m sure RS will make individual stanchions available at a reasonable price for when they get scratched. Ha ha ha – they will be exactly expensive enough that you might as well buy a new fork :D

    Looks cool though…

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