2021 Alchemy Arktos 120 XT 12-Speed 29 Bike

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Colorado-based Alchemy Bikes have been producing premium carbon and titanium frames since 2008. Last year, they introduced the Arktos 120, designed to be the perfect short-travel weapon that motors up climbs and promotes aggressive riding on the way back down. Utilizing Alchemy’s patented Sine Suspension system with only 120mm of rear-wheel travel matched with a 130mm fork, the Arktos 120 isn’t exactly a trail bike or a cross country bike. However, skimming over the component spec and geometry, it’s clear the smallest Arktos in the family takes cues from its longer travel siblings and puts a premium on downhill performance. As the heaviest bike included in our Short Travel Test Sessions, we were eager to see if the burlier build would pay dividends on the descents without significantly hindering uphill efficiency.

Highlights

• Alchemy premium full carbon frame
• Sine Suspension System
• 29-inch wheels
• 120mm (4.7-inches) rear travel // 130mm (5.1-inches) fork travel
• Flip-chip adjusts head angle and  seat angle and allows mixed wheel setup
• 65.75 / 66.50-degree head angle
• 77.75 / 78.50-degree seat tube angle
• 437mm chainstay across all sizes
• FOX 34 Factory fork, Kashima, Grip 2 damper
• FOX DPX2 Factory shock, Kashima, EVOL 3-position adjust
• FOX Factory Transfer dropper post, 175mm (size medium)
• Shimano XT 12-speed drivetrain
• Shimano XT 4-piston brakes
• Shimano 180mm rotors front and rear
• Industry Nine Enduro S Hydra wheels
• 29x2.3-inch Maxxis Minion DHF, EXO casing front tire
• 29x2.3-inch Maxxis Minion DHR, EXO casing rear tire
• Super Boost+ 157 rear spacing with 12mm through axle
• Threaded bottom bracket
• Fully internal cable routing
• Lifetime warranty 
• Measured weight (size medium, no pedals): 30.4-pounds (13.7kg)
• MSRP: $5,999 USD (XT Build)

Arktos 120 Overview

The Arktos 120 is the shortest travel model of Alchemy’s full-suspension Arktos platform. The full carbon frame boasts Alchemy’s premium carbon construction that uses varying thicknesses of the highest quality carbon sheets laid up unidirectionally by hand. Each frame is built using tube-to-tube construction with a carbon overwrap process to finish each joint. The result is an extremely strong and laterally stiff frame that still offers some compliance in strategic areas to maximize comfort.   

Rolling on 29-inch wheels, riders can set up the Arktos 120 with a 27.5-inch rear wheel via a flip-chip near the lower shock eyelet. We did not explore the mixed wheel setup, but out of curiosity, we did change the flip-chip to slacken the head angle and drop the bottom bracket to create a more descent-focused geometry package. (More on that below). A neat option Alchemy gives riders is the ability to purchase a conversion kit to transform their Arktos 120 into an Arktos 135 or 150. The conversion kit includes an extended link and longer travel fork and shock to match the travel and geometry of their longer travel models. Who doesn’t love having two (or three) bikes in one? 

Other noteworthy frame details include oversized pivot bearings to help ensure longevity, internal cable routing, and a molded rubber protector on the chainstay to minimize noise. Lastly, the Arktos 120 features dual water bottle mounts. One is traditionally located on the inside of the downtube, while the other is on the bottom of the downtube. We have never been fans of mounting a bottle on the downside of our downtube since we ride where there is livestock and don’t want to risk getting who-knows-what in our bottle. However, the mounts are there for riders needing extra water. 

Sine Suspension System

The hallmark of Alchemy’s Arktos platform is their exclusive and patented Sine Suspension System. Designed by David Earle, the dual, short-link platform uses a one-piece rear triangle with an upper and a lower link. The lower link is unique in that it moves up and then down as the suspension moves through its travel. This movement creates a shock rate that begins regressive for the first 25% of travel, or roughly up until sag, to maximize climbing traction and small bump compliance. Then, the shock rate turns progressive during the middle portion of travel to maintain a supported, lively ride quality. For the last 15% of travel, the shock rate again becomes regressive to allow full travel to be reached and to counteract air shock ramp-up. Alchemy recommends 30% sag when setting up their Sine Suspension system across all Arktos models.

Geometry

In our test group of four bikes, the Arktos 120 was the only bike we rode in a size medium, while all other bikes were a size large. However, with a 471mm reach, the medium was on par with our other test bikes, which fell between 470 and 478mm. Had we gone with a size large, the reach jumps up to 493.5mm, and the Arktos would have been an outlier in the group. It’s worth noting that Alchemy does not offer a size small. The size medium is intended for riders between 5 feet, 5-inches, and 5 feet, 10-inches, and we would urge shorter riders to test ride an Arktos 120 before purchasing as the bike does run big.    

Across all sizes, the Arktos 120 features a 437mm chainstay length, a 333mm bottom bracket height with a 40mm drop, a 65.75-degree head tube angle (low, slack flip-chip position), and a 77.75-degree seat tube angle (low, slack flip-chip position). With the flip-chip in the low, slack position, the Artkos did have the slackest head angle in the group.

XT Build Kit

The Arktos 120 comes in three build options, ranging from $5,499 to $6,499 USD. We tested the mid-range XT build that retails for $5,999 USD. As the name suggests, components included a Shimano XT 12-speed drivetrain with XT brakes. The Scott Spark 910 and Ibis Exie also used XT brakes, but the Arktos was the only bike to use the 4-piston version, which provided a bump up in stopping power and consistency. Across all three builds, Alchemy specs FOX Factory suspension and a Factory Transfer dropper post. Each test bike used different iterations of FOX’s Float 34 fork, and the Arktos boasted the premium model highlighted by FOX’s Grip2 damper. Out back, the Arktos sported the only piggyback reservoir shock in the group with FOX’s Factory DHX2.

Rider Setup

During our two-week testing period, conditions ranged from loose over hardpack to wet and tacky topsoil. Each tester began with Alchemy's recommended 30% sag and then made adjustments to match their preferences and trail conditions.

On The Trail

Our Short Travel Test Sessions was conducted throughout the foothills of Boise, Idaho. The trails immediately outside town feature flowing single track with high average speeds and occasional rock gardens. An aggressive, heavy bike with slack geometry is often too much. Instead, mid-weight bikes equipped to attack punchy climbs and carry speed on undulating terrain provide the best trail experience. 

Descending Performance

The Arktos 120 was hands down the fastest descending bike in the group, providing excellent stability and confidence that urged us to attack descents faster. What helped set the Arktos apart was its downhill-focused build kit, impressively stiff frame, and super-efficient suspension design. Despite being the heaviest at 30.4-pounds, we found the Arktos carried the most speed on low-angle trails. The rear suspension was incredibly supportive, making it easy to pop over rocks or pump through corners. Getting on the pedals took a tad more energy to get up to speed simply due to its size, but power transfer was immediate, and we never felt bogged down sprinting. 

Diving into more demanding sections, the Arktos still reacted like a 120mm travel bike. The rear suspension did not have a bottomless feel and tended to skip and deflect off rocks more than we would like. Adding to the sensation was the Arktos’ impressively stiff frame that provided a firm ride quality. Together, the frame and suspension created a fast and responsive bike on smoother terrain but hindered comfort and composure when trails got rowdy. Looking at Alchemy’s Sine suspension design, the increase in progression after sag could be the culprit, making the suspension too harsh on small-to-medium-sized compressions. 

Luckily, the Arktos build kit and geometry improved its ability to manage rough sections. Once we understood how the bike would react in such situations, we entered knowing we would have to be more deliberate with line choice and braking points. We rode in both geometry configurations, and the difference between each was marginal. We settled on the slacker position because the geometry package did not substantially affect climbing performance but complemented the Artkos’ descent-hungry mentality.

Climbing Performance

It wasn’t a big surprise that the Arktos 120 smashed descents, but we were shocked to find it flew up climbs too. Despite its weight, slack geometry, and meaty tires, the Arktos was a competitive climber against the other test bikes. The seated pedaling position felt like a mix of the Ibis Exie’s aggressive, attack position with the YT IZZO’s stood-up, relaxed mentality. The seat angle was steep enough to keep us neutral over our pedals while the wide and flat handlebars pulled our torso forward. In this position, we had no problem hammering up climbs and often forgot we were riding a bike more focused on shredding back down.

The firm rear suspension design also played a significant role in the Arktos 120’s climbing ability, providing a motionless pedaling platform that was highly efficient. The position of the rear shock in the middle of the frame made reaching the pedal-assist switch straightforward, although we rarely turned it on. With the shock open, the Arktos was plenty efficient, with enough give to dampen small compressions, making it easier to maintain speed. When locked out, we bounced around in the saddle and lacked traction. It was also hard to maintain a steady cadence. During our Efficiency Test, this sensation came to life as the Arktos was slower with the pedal-assist switch turned on. 

Build Kit

Alchemy did an impressive job speccing all Arktos 120 models with components that complement the downhill abilities of the bike. What’s more impressive is the value riders receive. Compared to our other test bikes, the XT build includes high-end components at a lower price that’s hard to beat. Even though the YT IZZO Core 3 tested was less expensive, we’d argue riders are getting a better bang for their buck with the Arktos. The closest priced bike was the Scott Spark 910, which for $300 USD more, comes with FOX Performance Elite suspension and less impressive wheels. We know $5,999 USD is not cheap, but if you have the funds, you will be jumping on a hand-crafted bike with premium components for much less than most brands can offer. 

Favorite Components - Shimano XT 4-Piston Brakes, Maxxis Tires, Industry Nine Wheels

A few components helped the Arktos 120 rise above the rest on descents without compromising climbing performance. Shimano’s XT 4-piston brakes provided an extra level of bite and consistency compared to the 2-piston model found on the Scott Spark 910 and Ibis Exie. Additional stopping control came from Maxxis’ Minion DHF and DHR II tire combo that sunk into the ground, finding more traction in our loose soil than the tires used on our other test bikes. The tires also gave us the cornering confidence needed to attack flat turns, allowing us to carry more speed on meandering trails. 

Looking at Industry Nine’s wheel line, Alchemy could have gone with their Hydra Trail S wheels and saved about 200 grams. However, the stiffness of the Enduro S wheels perfectly matched the responsive feel of the Arktos frame. The wheels offered excellent stiffness and support when landing off drops or leaning into corners and helped deaden vibrations through rock gardens. 

Least Favorite Component - Sella Italia Saddle, Tag Metals Handlebar

The Arktos 120 XT build kit was the only bike tested that we couldn’t find modifications we’d make to better match the intended use of the bike. But if we are being nitpicky, there are two simple touch-point adjustments we’d make to match our personal preferences. First, the Selle Italia X-Base saddle was despised by all our testers. Usually, we blame saddle discomfort on tester anatomy, but in this case, we had three different body types log painful miles on the X-Base. The main issue was the narrow profile and lack of a defined rear lip, making it tough to distinguish how far back we were sitting on the saddle. 

We also found the 20mm rise of Tag Metals T1 Carbon handlebar too low. The bend and compliance of the handlebar were enjoyable and not an issue, but rather we would have preferred taller handlebars to shift our weight rearward for added confidence descending.     

Test Sessions Take Away

Alchemy’s Arktos 120 might appear to be a slimmed-down trail bike with its slack geometry and descent-focused components, but don’t be fooled; the Arktos can haul ass uphill. The Sine suspension design creates an incredibly efficient platform, remaining almost motionless under pedaling forces but with enough suppleness to maintain traction up tricky climbs. Once gravity takes over, the Arktos 120 truly shines and was the most capable descending bike in our Short Travel Test Sessions. Highlighted by the ability to maintain speed on undulating terrain and generate momentum from the smallest trail features, the responsive frame and slack geometry creates a snappy and fast-rolling bike that is stable at speed. However, the stiff and supportive design will remind you it only has 120mm of travel in rough, demanding sections, requiring a methodical approach to technical sections that will keep many riders honest. With an outstanding bang-for-your-buck value, the Arktos 120 is ideal for riders wanting a short travel weapon that will carry speed in every situation and won’t shy away from blasting down descents. 

For information on the Arktos 120, please visit www.alchemybikes.com