Arc8 Extra 2.0: Lightweight enduro bike with exceptional rear triangle construction

First of all: The Acr8 Extra 2.0 is not a further development of the Premiere model. The successor is based on a completely newly developed frame platform. The centrepiece is the Arc8-typical rear triangle construction, which we already know from the siblings Essential and Evolve know. The damper linkage is therefore no longer handled by a conventional rocker link: two filigree guide cylinders transfer the forces from the rear triangle linearly to the damper.

Arc 8 Extra - the name says it all

In terms of stiffness and weight, the so-called slider design combines the positive characteristics of a short lever with the kinematic advantages of a very long bellcrank: the longer the bellcrank, the more linear the spring characteristic curve. As a result, the progression increases more evenly over the suspension travel, which in theory enables a very predictable response behaviour. In addition, Arc8 relies on flexing seat stays instead of additional bearings in the rear triangle design - except for the main pivot point. This reduces maintenance intervals and reduces weight. Speaking of weight: the carbon chassis weighs just 2025 grams in size M without the shock. A top value that puts the Extra 2.0 in the shade of most trail bikes. The geometry is also extra. The steering angle is extremely slack at 62.5 degrees. The 462 mm reach in size M is also orientated towards the long end of the size spectrum. Add to this a low bottom bracket, and the geometry of the new Extra raises hopes of an extremely smooth ride. The chainstays, on the other hand, are short. This should ensure that the long and flat bike retains its agility.

Practical test of the Arc8 Extra 2.0

The Extra's pronounced forward momentum is impressive from the very first pedal stroke. Thanks to its low weight, it is easy to get the bike up to speed. The seat angle is also very steep. It places the rider far forward on the bike. This makes it easy to distribute enough weight over the front when climbing. As a result, the Arc8 also climbs technical steep sections with ease. The rear suspension responds super sensitively and generates top traction. Also good: the chainstays grow with the frame size. This means that bikers of all sizes can enjoy a perfectly balanced geometry. However, the Swiss bike gets a big minus point in terms of efficiency: when pedalling out of the saddle, the suspension falls to its knees with every pedal stroke. That alone would not be a problem for such a powerful enduro bike. However, the fact that the Swiss have fitted the Fox DHX2 shock to the Extra without a platform lever dampens the otherwise successful climbing characteristics. This makes it almost impossible to stabilise the suspension on climbs.

The downhill riding position is also praised. The combination of low bottom bracket, high front and long reach integrates the rider safely and upright behind the control centre. Perfect for steep terrain! On high-speed sections, the extremely slack steering angle (62.5 degrees), paired with the generous reach for a size M, keeps the bike confidently on track. Thanks to the short 434 millimetre chainstays and the small rear wheel, fast corner changes, manuals and other tricks are still easy to handle. The tyre combination of Maxxis Assegai with sticky MaxxGrip rubber compound on the front wheel and a Maxxis Minion with robust DD casing provides excellent grip and plenty of puncture protection. So far, so good. However, we would have hoped for more in terms of the suspension's descending qualities. At slow speeds, on single bumps or hard landings, the rear end offers generous suspension travel. That's fine. However, as soon as the bumps hit the suspension faster, the rear end generously passes them on to the rider and sometimes even loses traction. Even with open compression damping and 35 per cent SAG, the suspension did not produce a plush ride feel during our tests.

Features and measured values of the Arc8 Extra 2.0

• Fork: Fox 38 Float Factory shock Fox DHX2 Factory
• Gear system: Shimano XT 1x12
• Gear ratio / bandwidth: 30; 10-51 / 510%
• Brakes: Shimano XT BR-M 8120 / 220/203 mm
• dropper post/stroke: Fox Transfer Factory / 200 mm
• Wheels: DT Swiss EX 1700 tyres Maxxis Assegai/Minion DHR II, 3C Maxxgrip Exo+/Maxxterra DD, 29 x 2.50/27.5 x 2.40
• Total weight: 14.74 kg (without pedals)
• Weight of wheels: 5554 kg
• Acceleration of running wheels: 4337 kg x cm²

Conclusion on the Arc8 Extra 2.0

The Arc8 Extra 2.0 follows in the footsteps of its predecessor and combines plenty of suspension travel with sensationally low weight. The geometry hits the mark. However, there is still room for improvement in the rear triangle. - Peter Nilges, BIKE Test Manager

Three questions for Jonas Müller, founder and engineer of Arc8

BIKE: In the past, Arc8 particularly stood out for its top values in terms of overall weight. Did lightweight construction play an equally important role in the Extra 2.0?

Jonas Müller: In fact, weight did not play a role in the development. The focus was on performance and durability. Only when we held the first prototype in our hands did we realise that we had once again built an exceptionally light frame. Despite the thick tyres, steel spring shock absorbers and large brake discs, the weight remains within reasonable limits even in the coil version. But the Extra is also available in an even lighter version with an air shock.

You are now also using your slider technology for the suspension of the Extra. What are the advantages of this rear suspension design on an enduro bike?

Especially on enduro bikes, the slider actually brings even greater advantages than with less suspension travel. In my opinion, the ideal transmission curve of a rear triangle is as straight as possible. In other words, the progression develops evenly over the entire suspension travel. To achieve this ideal, you need a very large rocker arm, which poses challenges in terms of construction, stiffness and weight. With the slider, we simulate a very long rocker arm with a compact component and thus avoid the disadvantages mentioned. The slider also keeps all lateral forces away from the damper.

What was the biggest challenge during development?

This may come as a bit of a surprise, but the storage compartment in the down tube is probably the result of more development hours than the rest of the frame. To put it simply: with a frame, we know what we're doing. With the storage box, we first had to acquire this knowledge: What should be transported? What does a good locking mechanism look like? How do you ensure that the lid always fits properly? How do you design the frame to minimise stiffness and weight? And these are just a few of the questions we had to answer.

Models and prices of the Arc8 Extra 2.0

In addition to two uncompromising enduro set-ups with steel spring shock absorbers, there are also two models with air spring shock absorbers. Instead of the thick 38 mm Fox forks with 170 millimetres of travel, they rely on a 160 mm fork with 36 mm stanchions. With this lighter setup, the Swiss are also targeting all-mountain riders, thus serving two target groups with one frame platform. All models are also available as a frameset (with shock). Arc8 also offers the naked frame for sale. Cost point: 3399 euros