The second generation ARC8 Extra enduro mountain bike introduces a unique sliding linkage, giving it a highly controlled leverage ratio with a very linear coil spring. It also gets the usual geometry refinements, but its the suspension that has us staring.
To understand why their slider is useful, it’ helps to understand where they were coming from with the Extra V1. They say with a traditional linkage system, you have a rocker arm rotating around a pivot as it pushes the shock into compression.
The longer the travel, the more extreme the link’s rotation has to be. Which makes it difficult to achieve a “falling rate” leverage ratio, which means the suspension needs less force to move it deeper into its travel. A falling rate design is useful with air springs because they require progressively more effort to compress as they’re, well, compressed.
Confusing terminology aside, basically a falling rate leverage ratio pushes harder on the shock as it goes deeper into its travel. Which makes it challenging to design a good linkage system on a long-travel bike when you want to use an air-sprung shock.
And it won’t work at all if you wanted to use a coil shock, which compresses in a perfectly linear fashion, since a falling-rate design would blow through that travel faster and faster as it gets deeper and deeper into its travel. But people like coil springs, so ARC8 needed a design that would create progression when paired with a linear coil shock.
And that design is the Extra V2’s Dual Pivot Slider Suspension System, which is adjustable to also work with air shocks.
Basically, the slider acts like an infinitely long rocker arm, which wouldn’t lose its leverage over the shock as it rotates…it just pushes straight forward inline with the shock. The design is somewhat modular…change the shock stroke and you change the travel and the progression. A grease port makes it easy to service without disassembly.
There’s also a flip chip that lets you offset the main pivot to adjust anti-squat, ranging from 102% to 140% at 30% or 35% sag when switching between 27.5″ and 29er rear wheels. This accentuates the more playful nature of a mixed-wheel build, or increases pedaling efficiency in 29er race mode.
They offer three builds, two with the coil shock and MX wheel setup, set at 170mm travel front and rear. The other uses an air shock, 29er wheels, and has 160mm travel. But, you can run it in either travel with either suspension type if you want, these are just the stock build offerings.
Overall, the bike is a bit longer and lower, and now come with size-specific chainstays. The reach is slightly longer, but stack is much higher to keep you looking forward and help you lift the front wheel off the ground. Seat angle is 2º steeper at 78º, which helps center you on the bike and provide a more powerful pedaling position.
They also set the bottom bracket 8mm lower to take advantage of more riders running shorter cranks (and, thus, they recommend running shorter cranks!).
There’s an internal downtube storage box with a sealed cover holding bottle cage mounts. Two pockets are included to hold a tube, tire levers, and mini pump (and keep them from rattling about).
Other features include:
- BSA threaded bottom bracket
- 4-piston post-mount brake mounts for 203mm rotors
- Standard Boost rear axle spacing
- UDH derailleur mount
- 31.6mm seatpost diameter
- 2.5″ max tire size recommended (2.6″ depending on tire)
The new design has a straighter seat tube, too, so you can run longer travel dropper seatposts.
In a refreshing backpedal, they moved away from the prior model’s integrated cable routing through the headset. Now, cables run into the headtube through traditional ports, and the opening for the storage box makes them easy to route through the frame and BB, too.
It comes with an adjustable chainguide, plus thick rubber protection on the chainstay and downtube. It may look slim and light (frame weight is just 1,545g raw), but it’s rated for use on the toughest courses and bike parks. Total frame weight painted with all hardware and a Fox Float X Factory rear shock is 2,550g.