Interbike 2015: Alchemy launches 27.5 Arktos trail bike

New suspension design claimed to deliver bottomless travel

27.5 All Mountain Trail Interbike

Interbike Mtbr

Frame and shock will sell for $3750.

Frame and shock will sell for $3750 (click to enlarge).

It’s unlikely most fat tire aficionados have heard of Alchemy. The Denver, Colorado-based bike builder made its name crafting custom carbon road and cyclocross steeds. But thanks to a lending hand from suspension guru Dave Earle that may soon change.

Meet the new Alchemy Arktos (Greek for bear), a 27.5” 150mm trail bike with a Boost 148 rear end that has a unique suspension design that’s claimed to deliver both climbing stability and bottomless travel in one sexy carbon frame package.

Dubbed Sine Suspension (as in a sine wave), Alchemy says the bike benefits from a unique shock ratio curve where the rate is regressive to the bike’s 30% sag point, then ramps up prior to switching back to a regressive rate 85% into its travel. This regression is designed to counteract the progressiveness of an air-sprung shock, meaning the full travel is used — but the midstroke is still supportive.

Chainstays are 438mm.

Chainstays are 438mm (click to enlarge).

“People in the off-road cycling world don’t often think about regressive suspension, and when they do they think of it being too soft,” said Earle, who played a role in the design of Yeti’s popular Switch suspension. “On a mountain bike, using regressive suspension in the negative travel gives the bike a much softer feel and incredible traction over small bumps, where other bikes would just skip across them. For example, the off-road racing Baja trucks have something like four feet of negative travel. When the air shock is ramping up at the end of its travel, the regressive shock rate comes back into play. The change from positive to negative and back to positive is what separates Sine from conventional dual-pivot suspension.”

The sine curve of the new Sine suspension.

The sine curve of the new Sine suspension (click to enlarge).

Alchemy claims Sine is unlike other dual-link systems (say, Santa Cruz’s VPP). But it was the recent expiration of the VPP patent that allowed Earle to implement the new design. The full composite Arktos’s front triangle is made at Alchemy HQ in Denver, while the rear comes from overseas.

Head-tube angle is variable depending on frame size, which compensates for reach variance and in turn improves front end control. Size small are the slackest at 66 degress, while the XL comes with a 67-degree head angle. Chainstays are a middle-of-the-road 438mm, and seat tube angle is 73.5 degrees across all four frame sizes, S-XL. Other features include internal cable routing and a threaded bottom bracket.

The Boost 148 rear end should help stiffen things up.

The Boost 148 rear end should help stiffen things up (click to enlarge).

Frame and shock will retail for $3750. There will be two standard paint schemes, but as with all Alchemy bikes, customers can choose custom paint combinations from 15 stock colors. Availability is set for the first quarter of next year, with complete bike specs and pricing to be announced later this year.

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This article is part of Mtbr’s coverage of the 2015 Interbike trade show in Las Vegas. For more from Interbike CLICK HERE.

About the author: Jason Sumner

An avid cyclist, Jason Sumner has been writing about two-wheeled pursuits of all kinds since 1999. He’s covered the Olympics, Tour de France, MTB world champs, and dozens of other international cycling events. He also likes to throw himself into the fray, penning first-person accounts of cycling adventures all over the globe. Sumner has also done extensive gear testing and is the author of the cycling guide book "75 Classic Rides: Colorado." When not writing or riding, the native Coloradoan can be found enjoying life with his wife Lisa and kids Cora and Tommy in and around their home in the MTB Mecca of Crested Butte.

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