Polygon Square One EX9 and its R3ACT Suspension

Polygon's Square One will be the first bicycle to feature the Naild's R3act rear suspension system, and the reason you need to know about this truly new design is that it rides like no other dual-suspension mountain bike you may have experienced. Big statement? Perhaps, but I have had the opportunity to trace the development of R3act 2 play, the first production version of the design, for three years running, and during that time, I watched some of the sport's heavy hitters scratch their heads in awe after riding the prototypes. More recently, I was given production-ready machines for final evaluation - an experience that made me wish I had not worn the words "groundbreaking" and "revolutionary" into cliches, because I have a proper use for them now. The Square One EX9 we introduce here has 180 millimeters of ultra plush rear suspension, but unless you were told, you wouldn't know that fact until you dropped into a rowdy descent. More about that later. 

Where did R3ACT suspension come from?

Today, we classify trail bikes by the amount of suspension travel that they possess. The reason is simple: as dual-suspension designs gradually progressed from 100 to 170 millimeters, riders either happily or grudgingly accepted a number of compromises between pedaling efficiency and suspension performance. Even with the addition of technological band-aids like anti-squat kinematics, pedal platform switches, remote travel adjustments, lockout levers, inertial controls and reactive electronics, experience has taught us that, at various waypoints, we trade pedaling efficiency for a more technically capable (and heavier) chassis, and we have names for those benchmarks of compromise: cross country, trail, all-mountain, and enduro.

Designer Darrell Voss thinks otherwise. "I don't believe that suspension travel should necessarily be part of that equation," says Voss. "Let's face it. Most riders are out there to have fun, and they can only afford one bike. If it pedals efficiently, what is the downside to having more travel?" Voss spent the past nine years working on a suspension system that erases nearly every downside of long-travel rear suspension. Heard that before? Yeah, probably from me, among others. Voss, who is a ripper downhiller, wanted an 180-millimeter-travel trail bike that pedaled as well as the best 120 bikes, but with a suspension that could track the ground like his DH machine. It took him a while, but he figured out a way to do it. It's called "R3act" - a tribute to Newton's third law - and it looks like it was derived from part of an alien space vehicle.

Why elevated chainstays?

Naild's carbon monostay swingarm is simply the most efficient way to provide an ultra-rigid structure that can incorporate the suspension's tubular sliding element. Shut your eyes and think "bicycle" and you will probably imagine a classic double diamond frame, garnished perhaps, with bits that relate to your style of riding. That's what a bike frame is supposed to look like, right? And, if you were making a frame from steel or bamboo, the double diamond design would be the best possible, time-proven way to build it. The addition of long-travel suspension, however, and the availability of engineered materials, like heavily manipulated aluminum or carbon composites, encourage designers like Voss to deviate from accepted fashion in order to solve new engineering challenges in more effective ways.

 

 

And the sliding element?

OK, here's the nerdy part: Voss admits that the basic concept is not new, and sources two bike designs that used sliding elements to help isolate the suspension from pedaling-induced chain tension: Paul Turner's Maverick and the evolution of Yeti's sliding carriage and present sliding column suspension. His version, however, takes the concept further. The heart and soul of his R3act suspension is a large stanchion tube that pivots near the bottom bracket that the monostay swingarm slides on. The stanchion tube is angled precisely to direct chain tension to counter suspension bobbing, and also to provide an "anti-squat" vector that, unlike the present dual-link suspension designs, remains very consistent through the bike's gear range and suspension travel. 

No-fuss Suspension

Voss would be angry if I continued to baptize readers with suspension kinematics and techno-sermons about R3act. He's spent a measure of his life attempting to debunk the hocus pocus that marketing and media hacks have heaped upon a mechanism that he believes should be a simple to operate. "Sure, R3act's kinematics are complicated to describe," says Voss. "But, the rider should never have to think of that. Set the Square One's sag at 25-percent, get the low-speed rebound close and go ride. There is nothing else to do."

Truth is, that's all there is to it. No rubber bands in the air can, no knobs to fiddle with. In fact, Voss had to work closely with Fox to provide an X2 shock with almost no rebound and compression damping to optimize its performance. After testing, Polygon deemed the shock's platform lever unnecessary and eliminated it entirely. Voss calls it "Ground Tracking" suspension, because the way that R3act uncouples braking and pedaling forces allows the wheel to follow terrain so closely that most riders initially think something has gone wrong back there. 

Construction

Presently, R3act swingarms are made from carbon, which is probably the best use of that material. To boost stiffness, the monostay structure is intentionally boxy where space or clearance is not a concern, so the large, hollow part lends itself well to carbon composite manufacturing techniques. The shock is driven by an aluminum yoke that pivots on plain bushings. Lateral forces on the swingarm are controlled by an aluminum rocker link near the mid-line of the swingarm that controls braking inputs and counters lateral forces. The sliding element is a large-diameter hard-anodized aluminum tube which pivots on ball bearings inside a pocket, forward of the bottom bracket. There is no spring or damping assembly between the swingarm and the stanchion tube, it is simply a sliding interface that telescopes as the suspension cycles.

Square One Ex Technology

The Square One EX's offset seat tube and unusual bottom bracket support structure give the impression that the chassis has a very slack seat tube angle, but that is not exactly the case. Measured in a straight line through the saddle to the bottom bracket axle, the Polygon's effective seat tube angle is 73.5 degrees with the stock, set-back KS LEV dropper post, and one degree steeper with a conventional zero-offset post in place. Polygon's reluctance to join the steeper is better seat tube movement is its only nod to conservative all-day trail riders. From there, the Square One's chassis reflects contemporary enduro numbers with a generous reach, a sufficiently low bottom bracket good stand-over clearance and a 66-degree head tube angle.

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