Argonaut Cycles custom monocoque carbon fiber road bike

Our latest project bike is a full custom carbon fiber road bike from Argonaut Cycles, a unique builder out of Portland, OR. Given the custom nature of the bike, we decided to start the project by exploring how they started, what makes them special and how their bikes are made.

The brand started out as a one man shop, with founder Ben Farver building steel bikes and loving the material. The transformation from the most classic of frame materials to the most modern, carbon, is unique among custom builders, and it’s damn cool.

Most custom builders use time- and labor-intensive tube-to-tube construction and years of layup experience to create a bike tailored for each individual customer. By contrast, most major brands use monocoque molds and assembly lines to quickly and cost effectively create frames that work (quite well, in most cases) for the vast majority of riders. Argonaut takes the best of both worlds to create something that’s shapely, unique and absolutely hand crafted for each customer.

We’re quite fortunate to be getting the fruit of Ben’s labor in for review, which will serve as the test platform for several very nice parts, like Dura-Ace 9000 11-speed and new Ritchey Superlogic bars and stem, among others. The build will unfold over the next couple months, culminating in a long term review.

But, it all starts with the frame, and here’s how Argonaut makes them, one by one…

Argonaut Cycles custom monocoque carbon fiber road bike
Flanked by current carbon Argonaut frames are an original steel frame and a 3D printed frame prototype.


“I got into steel bike building first,” said Farver. “I worked in bike shops growing up, then got into structural welding and building. But I wanted to get back into bikes, so in 2007 I started making frames. After making steel bikes for about three years, I realized the custom steel bicycle market was saturated, and that a lot of the business models used by small builders had a lot of flaws.

“I also found that a lot of the tube-to-tube construction methods used by others created some good bikes, but it didn’t take full advantage of the benefits offered by carbon fiber. I wanted to use the same technologies used by the big three, but offer it in fully custom frames.

“I had the business idea, but it took a long time to find the right partner to bring the concept to fruition. Eventually, I found ICE (Innovative Composites Engineering). They’re in Washington state, and all of the tooling and frame parts are made there. Andrew Stewart makes the tooling, and in our video (embedded at bottom of post), Andrew Redden’s laying up the parts and making them there. After that, I get them in my shop in Portland, OR, and do the actual frame construction.

“The goal was to take the latest technology and materials to make the highest quality parts, then put them together in a really nice riding bike. We spent last May through September testing and prototyping materials and parts that would carry the feel and ride dynamics of steel. It’s not as stiff in some ways, but it has more snap in others. We’re coming at it from a different angle. I really love how steel rides, and I wanted to start with that and improve from there rather just make a super stiff, super light carbon bike.”

Argonaut Cycles custom monocoque carbon fiber road bike


Settled on carbon, Farver then told us how he picks the particular types of carbon for each section of the frame. Most of the bike is built using layers of unidirectional carbon fiber sheets, but he specs 3K woven fibers in a few key areas.

“We use woven carbon in a couple different places. Carbon can have isotropic and anisotropic properties depending on the layup. When you use woven carbon, you can’t really control the flex and strength properties like you can with UD. But, it’s easier to cut and it handles vibrations better. So, we use that in the headtube because we don’t use any metal inserts or bearing races and it won’t fray when we cut it like UD would. Plus, woven carbon will fold and bend inside the bladder easier, so we use it in a few of the really tight bends on the frame.”

Argonaut Cycles custom monocoque carbon fiber road bike

They also wrap it around the “male” end of the sleeves to increase the bond strength, and ICE’s Andy Redden chimes in to explain why: “It’s essentially insurance on the bonds.  Whereas UD is essentially a flat material, weave has a third dimension on account of the fibers having to go over and under one another.  That way, instead of there being one large slip-plane for the a crack to propagate, it’s as though there are many small points of contact, with varying degrees of stiffness, so the bond is tougher.  You could liken it to Velcro.  A single, strong hook and loop may hold the same load as a strip of Velcro, but if it breaks, there’s nothing to hold the two pieces together.  On the other hand, you can tear apart the ends of two pieces of Velcro, and the rest of the pieces will still hold together.”

Argonaut Cycles custom monocoque carbon fiber road bike


The frame uses a tear drop shaped seat tube and seatmast with a custom topper. “I did this because I wanted to customize the seat post along with the rest of the frame because different weight riders have different needs, and this lets us control the comfort.”

There’s 2cm of adjustment using spacers, so you cut it where you need it, then you have some wiggle room if you ever change shoes, cleats or saddles.

All of the tubing sizes and profiles were chosen so we could make them light enough while giving us the ability to make it as stiff as we wanted it based on the rider. With a standard round tube, if you go too thin, you have to add so much material to make it stiff that it becomes heavy. If the diameter’s too big, it’s inherently very stiff, so for smaller riders we’d be making the tubes so thin you could poke a finger through them.

Argonaut Cycles custom monocoque carbon fiber road bike


All of the layups are created on the computer, then the shapes are cut out on a plotter.

“Every piece of the frame is molded into a portion of the bike. Think of them as individual pieces of the frame rather than just tubes. The top, head and downtubes are all molded as one piece, and each part of that frame section is laid up specific to the customer with certain ride and flex characteristics in mind.”

Argonaut Cycles custom monocoque carbon fiber road bike
One of the few bladder and mold pieces they're willing to show.

A latex bladder controls the internal shape of each section. Carbon is placed layer by layer upon the individual bladder, which lets them truly customize every single inch of the frame. It’s then put into the aluminum tool, which is then put into a heat press. As it heats, the bladder is inflated to an undisclosed pressure, which presses the pre-preg carbon into the tool while the heat melts the resin and fuses the layers into one. Once cooled, the bladder is deflated and removed.

The obvious question here is how they’re laying up carbon on a non-inflated bladder, and that’s a secret they’re not willing to give up.

Another secret is how they’re able to get different angles and lengths of parts like the headtube. At the heart of any custom bike is angles and tube lengths made to fit the rider, which is like oil to monocoque’s water. To get around this, their tooling and internal bladders are designed such that they can make the different angles and lengths inside the tooling. It’s cool, we’re just not allowed to show you.

Once the geometry is planned out, it’s all about the layup and materials selection.

“We’ll use different combinations of modulus as well as how the fiber is oriented within the part. Those two things dramatically affect how the part will perform. For instance, within the downtube, we’ll add some high modulus and change the angles from, say, 30º to 45º to change the torsional stiffness.”

Argonaut Cycles custom monocoque carbon fiber road bike
L to R: Thick sheets of carbon are cut to shape, then placed in the metal molds to be pressed and heated. Click image to enlarge.

After the tube sections and frame parts are made, the dropouts are created using a different process. It’s called Compression Molded SMC (Sheet Molding Compound), which uses UD fiber “chunks” pre-impregnated with resin, heated and compressed into a mold.

Argonaut Cycles custom monocoque carbon fiber road bike

The result is a solid carbon part. You don’t get the same anisotropic qualities using SMC, you just get a really stiff part that’s also very light, which is why they make the dropouts this way rather than with just alloys.

Argonaut Cycles custom monocoque carbon fiber road bike

The actual dropout part in which the axle sits are 6/4 titanium, and the design serves two purposes. First, it creates a multipart system that allows you to replace one section if it bends or breaks but is still really light. Second, the metal dropouts and hanger allow for a more durable contact point for skewers and hub axles. The inserts between the carbon dropouts and seatstays are alloy. The two parts bolt together to make it easier to get the angles right. They’re not titanium because they don’t need to be that strong, so there’s no need for the added cost there.

Argonaut Cycles custom monocoque carbon fiber road bike
L to R: A sliding dropout just for fun, the titanium dropout section and an original, pre-carbon alloy dropout section.

Argonaut Cycles custom monocoque carbon fiber road bike

Once all the pieces are ready to be assembled, Ben preps all the pieces by cutting them to length, adding water bottle bosses, cable stops and front derailleur hangers. The “male” end of the sleeved sections are created during the molding process. The “female” ends, like the rear part of the top tube, are molded a little longer than necessary then cut to size.

Argonaut Cycles custom monocoque carbon fiber road bike

Argonaut Cycles custom monocoque carbon fiber road bike

Cable stops are both bonded and riveted on. Ben says the bonding agent has super strong sheer strength, but “peel” strength isn’t quite as good, so the rivet is added to make sure they don’t come off.

Argonaut Cycles custom monocoque carbon fiber road bike

They use a two-part aerospace adhesive that permanently bonds the two sleeved sections together. Ben says the glue is actually stronger than the carbon.

Argonaut Cycles custom monocoque carbon fiber road bike

Ben says the assembly process is pretty straightforward. “The really cool part of the story is how the frame pieces are molded. That’s where the real value of these bikes is. By making the parts the way we do, you end up with something really special that no one else makes.”

From start to finish, it takes about three days to layup, mold and create the parts for one bike. It then takes about two days for everything to be assembled, including all the prep, finishing, cutting and adding external bits. Once it’s all put together, there’s finishing of the bond areas to make it clean and smooth. At room temp, the epoxy would take about seven days to cure, but Ben puts it in an oven (the silver box in the background, above) at 150º and it’s cured in an hour.

Argonaut Cycles custom monocoque carbon fiber road bike

Before assembly and after final construction, all parts of the frame are checked for flaws and alignment.

“Before sending it to a customer, we check the frame’s alignment, and before I build the frame I check all the parts for both structural and aesthetic flaws,” Farver says. “A structural flaw might be something like a fold or crease in the laminate, which creates a stress riser and could potentially result in a crack. An aesthetic flaw might be something like a dry spot on the surface of a part where the resin didn’t completely make it to the confining surface of the mold, or a small bubble between sheets of pre-preg. The quality of a frame has 99% to do with the quality of the parts, so most of the testing goes into guaranteeing each individual part’s viability. The bonding areas are in the lowest stress area of a frame part intersection, and overbuilt both in terms of the surface area of the bonding surface and the strength of the epoxy, so there’s not much room for error there.”

After the final check, it’s off to paint…

Argonaut Cycles custom monocoque carbon fiber road bike


Base coat clear, then sanded and logos are placed, then a second clear coat is applied. His frames are painted at COAT, which is owned by Vanilla’s Sacha White.

Argonaut Cycles custom monocoque carbon fiber road bike

Argonaut Cycles custom monocoque carbon fiber road bike

We’ve seen the finished product, and it’s sweet…but we’re going to save that until it shows up at the Bikerumor office for build up, weigh in and first impressions.




  1. Really like the concept here as it pertains to custom. This does not look like RTM process to me as they seem to be using prepreg sheets. This seems like a custom take on how the Trek Madone is made from sub assembley of parts rather than individual tubes. Thumbs up for me

  2. @ “me”

    That is not that strange if you are trying to run a gates belt drive system with the changeable drop out system shown. If you are unbolting the seat stay to separate and change the belt drive I personally would rather have metal for the treads even if you can tap and thread bolts in carbon. I think it is a very forward thinking design, and using the same on both sides should save some production costs. Easton does the same thing with the EC90 rear triangle they produce for builders.

  3. @Rob

    This is not Resin Transfer Molding. This is pretty proven stuff, though done in a slightly different way. If you don’t trust this, then you don’t trust carbon bikes.

  4. @ NCMTB

    me is correct, though – the carbon dropout does not allow you to split the frame in any fashion that would allow a Belt drive. It does let you swap geared/single speed/disc brake dropouts, though, so it’s understandable from that perspective.

  5. @ Androo

    Look at the second, third and fourth picture below the bladder picture. The carbon seat stay has a ti plug that bolts to one piece carbon SMC drop out part. You can un-bolt the SMC drop out part from the seat stay with black Allen bolt as pictured in number two effectively splitting the drop out from the seat stay. In your perspective you are only looking at the carbon drop with removable bolt on hangers and not what “me” says the “carbon seat stay bonded to metal plug bolted to carbon intermediate dropout bolted to metal dropout”. There are frames out there that split the drop out in half to use belt drive, so it understandable you would look at that way.

  6. @kenben
    wow that isnt the same at all. that bike is clearly tube-to-tube which is the standard way custom carbon is done.
    i am surprised that they can get a high enough quality on the internal of those tubes to join them the way they do so kudos there. however i have seen multiple trek frames (built much the same way) crack along what are ATMO stress risers created by those bonds. these frames probably would have cracked regardless due to impact but i thought it was interesting

  7. I can’t help but wonder what adhesive he is using, almost certainly an MMA but why the temp cure cycle? Most wouldn’t need that…

  8. @ halr75

    Many folks who build with carbon use 3M DP420 or something of the like. Loctite makes something similar, but the same escapes me at the moment.

  9. It doesn’t seem like they are utilizing what trek has patented as their “step joint molding” (similar in concept but it has about 3-4 clearly defined steps in carbon thickness to get even more overlap) more of their own take, utilizing less variation between steps where the sleeves join.

    Great work and quality. After meeting Ben at sea otter, I’m sure my first custom carbon bike will be an argonaut

    It’ll be like a more custom version of my project one

    Sweet work guys!

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