ARC8 Evolve FS is a lightweight, developing XC MTB with flex stays and slider interruption.
The ARC8 Evolve FS is the latest addition to the brand’s lightweight cross-country mountain bike range, entering the market at a very competitive weight of 1.78kg (frame and shock), while the high-end XX1 build weighs 9.5kg. Size. For the XC bike, the evolution geometry is very aggressive; The head angle in the Slokest configuration comes in at 65 °, usually reserved for long-haul bikes belonging to the Trail or Enduro classes.
ARC8 Evolve FS
ARC8 tells us Evolve FS XC bike was something he wanted to do 4 years ago, because it is the kind of bike that co-founder Jonas enjoys riding himself. They are hindered so far because they are convinced that the market is not ready for such progressive geometry. Over time, a new class has emerged; Management Low country. Love it or hate it, it’s here to stay, but it doesn’t deny that the lines between the downcountry and cross-country classes are blurring at the rate of knots. ARC8 sees the evolution of FS as its embodiment.
The brand believes that the ARC8 Evolve has FS geometry and will be ubiquitous in the XC class in a few years.
In its most race-ready configuration, the Evolve FS has 100mm rear-wheel travel with a 100mm fork, but low-cost builds get a little more suspension travel; 110mm rear with 120mm fork. In both cases, rear-wheel travel is delivered through the new suspension platform, which relies on flexible seat stays and a shock driven by a slider mounted to the top tube.
We were delighted to meet with ARC8 co-founder Jonas Mueller at the Winter Bike Connection event in Italy, where they talked about everything they needed to know about Evolve FS, as well as some background on how ARC8 came about.
ARC8 Evolve FS Details
Bike: ARC8 Evolve FS
Purpose: XC / Marathon MTB Racing
Frame Material: Carbon
Fork Travel: 100-120mm
Rear Wheel Travel: 100-110mm
Wheel size: 29 ″
Weight: 9.5kg (right) XX1 medium build
Frame Price: 3,299 €
Jonas Mಲ್ಲller, formerly of ARC8 Branding, is an engineer who previously developed his own carbon mountain bike frames at BMC for 7 years. Most recently, Jonas is a bicycle. He was a frame designer for engineering, where he was head of the development of open moulded bicycle frames that were licensed to be sold by several brands. In fact, the very first ARC8 bicycle, the Essential, is one of the aforementioned open mould frames designed by Jonas. The Evolve Hardtail and Extra Enduro frameworks followed shortly thereafter.
While at Bicycle.Engineering and BMC’s factories in Taiwan, Jonas gained insight into exactly how carbon frames are made, and how to design frameworks with those manufacturing processes in mind. Although still manufactured in Taiwan, Jonas plans to bring carbon production to Europe.
In the four years since ARC8 was created as an independent bicycle brand, Jonas has been working on designing open-frame frames (and components for sister brand Fazer Week); The Evolve FS you see above is the first frame specific to the ARC8 brand.
The development of the Evolve FS did not come from the desire to make the Evolve Hardtail a complete suspension mountain bike; This is, in fact, the evolution of the Arc8 Essential, their 4-bar Linkage 120mm travel trail bike. Although the bike was never intended to be a full-fledged XC race bike, customers, especially those in Switzerland, were adapting it to the 110mm rear-mounted with a 120mm fork. In fact, Nicola Rohrbach spent two years racing on the original ARC8 Essential Frame, winning the Swiss Epic in 2021. In that marathon / cross-country configuration, full builds of 10.4 kg are possible.
Weight was never a major priority during the development of the original Essential, but the suspension design lends itself well to the lightweight design. Naturally, Jonas was intrigued to see how lightweight a full suspension XC frame can be if he set his mind to it. And so did they.
Sized Medium ARC8 Evolve Frame With Fox Float DPS Performance Weighs 1.775 Kg; The new design sees an 11% reduction in surface area in the front triangle and a 22% reduction in the swingarm.
In pursuit of shaving grams from an already lightweight Essential Frame, the ARC8 isn’t ready to compromise on wall thickness. To reduce the material, he chose to make the tubing smaller in diameter. Before they turned their attention to the suspension platform, they were able to save more than 250 grams by reducing the surface area of the frame.
With Essential’s four-bar link with its ten frame bearings and all the hardware that came with those pivots, the ARC8 was able to save a further 118g. Jonas and the engineering team were happy to save more than 368g without compromising stiffness or strength, and without damaging the frame too much.
The Evolve FS carries the reverse main pivot found in the original Essential, in which the stays sit inside the seat tube and the bearings are kept in place. The retracted portion of the seat tube, which is blocked by the view through the stay, is actually open, but is enclosed in the Essential Frame. Now, there is no risk of debris being trapped and potentially damaged. The debris can of course enter the lumen of the anterior triangle, but there is a hole in the bottom of the dentube that allows it to escape.
Another place where the ARC8 can save weight is on the brake mount, which switches from the post-mount on the seattail to the flat-mount on the chainstay. With the new suspension design, the seat is curved when the bike is pushed through its rear wheel.
Essential’s four-bar link is replaced by a suspension platform that relies on Flex Seat Stays, and a slider is mounted to the upper tube that guides those Flexing Stays to drive the rear shock. Through Link, this setup allows the bike to create a more straightforward possession curve throughout the entire rear journey, while the four-bar linkage designs lack the classical sine-shaped curve traditionally derived.
Jonas is able to tune the progression by changing the angle of the rails sliding along the shock. Similarly, moving the rails up or down will increase or decrease rear wheel travel. Changes the anti-squat level in the system that moves the main pivot. The amount of friction the slider adds to the whole system is said to be low; Jonas says that if you remove the slider and hold the rods in your hand, the shock mount tab that slides along those rods will move along their own weight.
In the unloaded condition of the bike, the seat stays distorted. It sits somewhere in the middle of the bike’s 110mm rear-wheel drive, where flex stays are lowered, and they begin to bend in the opposite direction during the second half of the journey.
Evolve FS geometry
Built with 100mm travel, the ARC8 Evolve FS XX1 RockShox receives the SID SL Ultimate Fork and the SID Lux Ultimate Shock, each with a remote lockout. The claimed weight is 9.5 kg with the ingredient you see here.
The ARC8 Evolve FS can be built as an all-out XC racing bike with a 100mm rear-wheel drive and 110mm fork, or as a 110mm travel bike with a 120mm fork. In its short travel configuration the head angle is at 66.1 °, slowing to 65 ° in the long travel setup. The BB drop comes in 35mm and 43mm, respectively, and both chainstays at 430mm in frame sizes.
Unsurprisingly, it is only available in medium and large sizes, accommodating riders of 160-190 cm height. Jonas tells us that he originally planned to bring the smaller frame to market, but riders below 160 cm thought that the mid-frame 465mm range delivered a very comfortable fit. After consulting with the Swiss Olympic team doctor and renowned bike fitting expert Andreas Gossele, the ARC8 team concluded that there was no need for a smaller size.
That 465mm reach is tied to the middle frame with a 120mm fork; In a more race-driven low-travel setup it increases to 477mm. The larger frame range comes with a 120mm fork at 495mm, with a 100mm fork to 507mm.
Evolve FS frame details
Another place where the ARC8 can save extra weight is in the lower bracket; A PressFit BB allowed him to reduce the amount of material here, but Jonas chose not to go this route, instead opting for the reliability and improved durability that comes with the use of a thread bottom bracket.
Internal cable routing to headtube divides opinion, but does not require apertures in carbon for cable access
The Evolve FS is designed with a focus on internal cable routing, and clean-cut aesthetics also seem to be important. ARC8 has worked with Across in the custom headset cap, which adds cables and hoses to the headtube.
While this is not obvious in any of the photos here (mostly thanks to that matte paint job), the bottom of the downtube is actually aerodynamic, with little surface area in the direction of travel. More importantly than aerodynamics, Jonas tells us that this feature helps prevent the downtube from holding more trail debris when the downtown is racing in very muddy conditions, again helping to reduce the weight of the bike.
The Evolve FS Boost (148mm x 12mm) has rear end spacing, resulting in adequate clearance for the 29 ″ x 2.4 ″ Wolfpack Speed Tire. In the dropout, the SRAM UDH hangar supports a 12-speed derailleur.
Pricing and Availability
The ARC8 Evolve FS is available today as a retail bike at 3,299 or as a complete bike with three build options to choose from. The most affordable of those three is the Evolve FS XT, which costs 6,199. It gets a 12-speed Shimano XT drivetrain with XT brakes, a Fox 34 SC float with a FIT4 damper, a 120mm travel fork, a Fox Float DPS performance shock and a Newmen Wheel Evolution A.30 wheelset. It weighs 10.7 kg
In the middle of the range is the Evolve FS XTR retailing 8,999 €. It gets the factory-level Fox suspension and the Shimano XTR drivetrain and brake upgrades with the Newmen Advanced SL XA. 30 wheels. It weighs 9.8 kg.
The Evolve FS is the top model of the XX1 range that will return you 9,999, with a weight of 9.5kg. It comes with 100mm Travel Front and Rear with RockShox SID SL Ultimate Fork and SID Lux Ultimate Shock. It receives SRAM XX1 Eagle AXS drivetrain, Magara MT8 SL brakes and electronic shifting in the form of the Newmen Advanced SL X.A. 30 wheels.
For more information on Evolve FS models and prices, go to the ARC8 Bicycles website.