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The Actofive I-TRAIN is a Short-Travel Weapon for XC, Downcountry or Trail

actofive i-train short-travel mountain bike adjustable rear wheel trave mullet capable cnc machined front triangle
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Actofive has released a “fast full suspension frame”, named the I-TRAIN. It is a short-travel mountain bike able to run 105mm, 115mm or 125mm rear wheel travel paired with 120-140mm fork travel. Its versatility delivers a platform that can switch between XC, Downcountry and Trail riding intentions.

actofive i-train short-travel aluminum mtb designed by simon metzner cnc machined front triangle mullet capable green frame

Actofive I-TRAIN

The I-Train is borne of a collaboration between CNC specialists, Actofive, and Nicolai, another German mountain bike manufacturer famed for its progressive-geometry long-travel mountain bikes. Actofive produce the stunningly beautiful front triangle, composed of two CNC-machined halves of 7075-T6 Aluminum, bonded together with adhesive for a lightweight, hollow construction. Nicolai produce the aluminum chainstays and seat stays. Designer, Simon Metzner, claims this is the lightest CNC-machined frame in the world at a claimed 2,750g (without shock); the front triangle weighs a claimed 1,200g.

actofive i-train suspension linkage horst-link layout mullet capable travel adjustable
Maximum tire size on the Actofive I-TRAIN is 29″ x 2.4″

The I-TRAIN runs a Horst-Link suspension layout, with a kinematic that, as the name might suggest, prioritizes pedaling efficiency. There are three recommended configurations, made possible by three unique rocker links and two different shock dimensions:

  • With a 190mm x 45mm shock, the I-TRAIN can run 105mm of rear wheel travel; paired with a 120mm fork and a 29″ wheelset, this configuration is best for XC or Downcountry riding
  • Again, with a 190mm x 45mm shock but a different rocker link, the I-TRAIN can run 115mm of rear wheel travel; pair that with a 130mm fork and you have yourself a more trail-focused mountain bike
  • Lastly, with a 210mm x 50mm shock and an alternate rocker link, the I-TRAIN can run 125mm of rear wheel travel, but only with a 27.5″ rear wheel; this one is a dedicated mullet, recommended for use with a 140mm fork for “a playful yet efficient bike for those man-made obstacle-focused rides”
actofive i-train short-travel mountain bike adjustable rear wheel trave mullet capable cnc machined front triangle
For a short-travel bike, the Actofive I-Train has a relatively steep seat tube angle of 77°; the tube is straight and uninterrupted to allow riders to run long-travel dropper posts

Actofive I-TRAIN Geometry

The Actofive I-TRAIN is available in three sizes, with reach figures of 450mm, 470mm and 500mm to choose from. All get the very same chainstay length of 437mm.

actofive i-train non drive side view horst-link
Note the BB height-adjusting flip-chip at the lower shock mount

Outwith the rear wheel travel and wheel size adjustments, one also has the freedom to tweak the I-TRAIN’S BB Height over an 8mm range; a flip-chip at the lower shock mount alters the chassis height through 329mm, 333mm and 337mm. Actofive say this relatively low BB height lends itself well to cornering composure, and with such a short-travel bike, pedal-strikes shouldn’t be an issue.

actofive i-train head angle adjust headset

Thanks to the inclusion of a +/- 1° ADJUSTABLE RIDE angleset, the I-TRAIN can also be set up with a 65°, 66° or 67° head angle, dependent on the rider’s preference, or the steepness of the terrain on the menu that day.

This geometry chart pertains to the Actofive I-TRAIN running a 29″ wheelset with a 130mm fork; with a 140mm fork, the HA and SA slacken off by 0.45° and the BB height increases 3mm

I-TRAIN Kinematic

In its longer-travel configurations, the I-Train’s leverage curve is really quite progressive, especially in the 125mm configuration with the 27.5″ rear wheel – see the pink line in the Leverage Ratio graph provided by Actofive below.

This one sees the highest starting ratio and lowest end-stroke ratio, in-line with its more rowdy trail riding intentions; Actofive say this leverage curve is also amenable to use with a coil shock. For the XC-oriented 105mm configuration, the leverage curve flattens out considerably.

In the 14T cog of the cassette with a 32T chainring, the I-TRAIN sees an anti-squat value of just over 100% at sag, rising very steadily thereafter. Such a kinematic should deliver a very efficient pedaling platform that results in negligible pedal-induced bob. Anti-rise is on the lower end of the scale, sitting at around 50% at sag, which indicates that the front-to-rear balance of the I-TRAIN’s chassis will not be unaffected by heavy braking.

“It’s not about waiting until you reach the top of the trail. On the I-TRAIN every part of the ride is a game! …The bike grips so well that sometimes I forgot I’m not on my enduro bike and went big anyway… That was wild!”

Vojtěch Bláha
Vojtěch Bláha is a Czech athlete sponsored by Actofive; he races the Enduro World Series (now the UCI-EDR) aboard the Actofive P-TRAIN

Key Frame Details

  • Derailleur Interface: SRAM UDH
  • Spacing: BOOST 148mm
  • Max Tire Size: 29″ x 2.4″
  • Headset: IS41/28.6 – IS52/40
  • Seat Tube Inner Diameter: 31.6mm
  • Seat Clamp: 34.9mm
  • Max Seatpost Insertion Length: S: 240 / M: 270 / L: 300 [mm]
  • BB: 73mm BSA
  • ISCG-05 Tabs
  • Brake: PM 180
  • Bottle Mounts: 1 x Downtube topside + 1x Toptube bottomside
  • Cable Routing: Internal, External or Mixed

Pricing & Availability

The Actofive I-TRAIN is available in a raw aluminum finish, or in nine different anodized colors. Frame price, excluding shock, is 4,950 EUR (excl. VAT). Delivery can be expected 12-20 weeks after order placement. Each frame is sold with a 5-year warranty.

actofive i-train frame cnc machined aluminum hollow construction lightweight short-travel mtb xc downcountry trail riding

Finally, we leave you with what creator, Simon Metzner, has to say about his Actofive I-TRAIN: “I am proud of being independent and free to pursue ideas that truly fascinate me as MTB rider. With my company METZNER Engineering Ltd., we’re experts in engineering and CNC machining. It’s great that ACTOFIVE is now the majority of our work. The I-TRAIN is the latest coup in the ACTOFIVE lineup and fulfills my personal dream of a light and fast CNC bike – and by the way, this is the lightest CNC frame on earth! I love my I-TRAIN for all-day-epic, trail focused rides and as the perfect complement for my big hitting P-TRAIN. With its variability, it offers me the perfect platform to test different setups, because I’m really into experimenting. Right at my local riding spots, it reawakens mellow trails to new life – bet you´ll have a blast on it too!”


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Deputy Dawg
Deputy Dawg
11 months ago

Looks fun and fast. For my tastes, a bit of a silly STA for a short-travel, high anti-squat bike.

Jason DW
Jason DW
11 months ago

Looks awesome!!! I would definitely ride that

Brad Comis
Brad Comis
11 months ago

Anyone know what stem that is?

Cory Benson
6 months ago
Reply to  Brad Comis

@Brad, a BikeYoke Barkeeper.

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