The ultimate All-Terrain Bicycle

Tire clearance: 29x2.6", optional clearance up to 27.5x3"
Dropout style: 3D printed UDH
Ideal uses: Backcountry gravel, bikepacking, door-to-trail mountain biking, off-road touring
Material: Titanium
Drop and flat-bar compatible

Designing and building custom bikes every day regularly inspires us to think of new ways to use our own bikes. As soon as we started building Ti forks, we started dreaming of the ultimate fully rigid all-terrain bike – a road-to-trail machine that would be more capable on MTB trails than a gravel bike, and faster and more comfortable on roads than a mountain bike.

We wanted to commute through the woods on it, take it bikepacking and camping, and sometimes take it out for all-day gravel rides where we might just get in over our heads. While we were at it, we wanted it to look like the nicest fully rigid 90’s mountain bike we’ve ever seen (might as well lean into the inevitable comparison).

Enter: the Firefly ATB. 29×2.6” tire clearance with super short 430mm chainstays, configurable for any combination of bags, racks, lighting systems, and every other bikepacking feature you need, and, with the right components, even compatible with drop and flat bars on the same bike. Here’s how we pulled it off…

Big tires and short chainstays create two issues. First, how do you fit the chainstay in the tiny gap between the tire and chainring? Second, if the chainstays are really short, how do you create enough tire clearance behind the seat tube? A curved tube is the obvious answer, but bending a 35mm Ti tube limits our flexibility to customize the tube’s wall thickness and makes it harder to create a precise seat tube angle. Our 3D Clearance System solves those issues.

The 1x specific yoke threads the gap between 29×2.6” tires and up to a 40t chainring with a 52mm chainline, all with super short 430mm chainstays. (The design also gives us flexibility to accommodate up to 42t chainrings with a 47.5mm gravel chainline, which just reduces tire clearance to 29×2.2″. Choose our Gravel model for bigger chainrings.).

The 3D printed seat tube knuckle then shifts the seat tube forward, creating space for the tire behind the seat tube while giving the frame a perfectly consistent seat tube bend for a precise frame geometry and saddle position every time. The short design of the knuckle also allows for a longer straight segment above the bend than with a simple curved tube, leaving plenty of space for long travel dropper seatposts.

UDH dropouts are a must-have for a bike like the ATB, making it compatible with the latest and greatest 1x drivetrain components. We collaborated with our designer, Josh Ogle, on a UDH dropout design that is compatible with flat-mount and post-mount brakes, works perfectly with every drivetrain system available, including SRAM Transmission, and retains an undeniable Firefly style.

UDH dropouts are a must-have for a bike like the ATB, making it compatible with the latest and greatest 1x drivetrain components. We collaborated with our designer, Josh Ogle, on a UDH dropout design that is compatible with flat-mount and post-mount brakes, works perfectly with every drivetrain system available, including SRAM Transmission, and retains an undeniable Firefly style.

Flat bars give you more control on rough trails, while drop bars give you more hand positions for long-ride comfort. As our vision for the dream ATB formed, we realized that building the bike to work with both handlebar styles would make it exponentially more versatile.

With the right component and design choices, including careful selection of handlebar shapes and widths, wireless shifting, and couplers in the brake lines, you can switch from mountain to drop bars in less than 10 minutes and without any brake, shifting, or fit adjustments. Any given ride, simply choose the bars that match the day, and you’re on your way.

Most mountain bikes have suspension forks or suspension-corrected rigid forks. Suspension forks are long, typically at least 10cm longer than gravel forks. The big downside of such long forks is that they can force the bars to be too high and limit our flexibility to customize the bike’s fit. That’s not usually a problem for a pure mountain bike, but for a bike like our ATB that is purpose built for longer rides on more varied terrain, a precise fit is just as important as it is on road and gravel bikes.

That’s why one key to the ATB’s versatility is using a relatively short fork without limiting tire clearance, allowing us to get the handlebar height correct for every fit and giving you the traction and comfort of wide tires. Our ATB will come standard with Whisky No.9 MCX+ fork, a great carbon option with a 430mm axle-crown height and space for 29×2.6” tires, cargo mounts, and internal dynamo wire routing. Or, for the best possible ride quality and handling, upgrade to our brand new ATB fork, with clearance for 29×2.6” or 27.5×3” tires, and available with custom offsets, cargo mount options, and finishes to perfectly match your Firefly frame. (Other forks available on request as well.)

Pricing

Custom frameset price, titanium :: $5,500
Complete custom bikes, titanium :: $8,500-$13,000+

STANDARD FEATURES

Fully custom frame geometry and tube selection
Meticulously TIG-welded construction
Firefly 3D Clearance System for 29×2.6″ tire clearance with 430mm chainstays
73mm English-threaded BB
44mm head tube for tapered forks
Firefly UDH 148x12mm Boost thru-axle dropouts
Whisky No.9 MCX+ carbon fork

OPTIONS

Firefly ATB Ti fork // $1850
Internal Di2 routing // $200
Internal brake routing // $350
Tapered head tube // $100
Internal dropper post routing // $250
Pressfit30 or T47 BB // $75
Custom frame bag mounts // $100
Integrated light wiring // $200
Rack mounts // no extra cost
Travel couplers // $1300
Pinion gearbox mount (new!) // $750
Bosch ebike upgrade // complete builds start at $9200 (only available on full ti bikes within the US)

The bike fits me perfectly, and it is very pleasant indeed to ride. The place where I have noticed the excellent handling the most is on fast descents on gravel. I feel completely confident of what the bike will do, and I feel no insecurity.

See the build
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