Myth Cycles: Frame builder Eric Tomczak shows how to build your two-wheeled dream machine

Words and photos by Ben Brashear

There aren’t too many custom bike builders, let alone bike companies, that broke into the market by building a tandem mountain bike. Everyone has heard the saying that tandems will end your relationship, but for Durango, Colorado bike builder Eric Tomczak, it was the very thing that helped to define his relationship and the very ethos of his company, Myth Cycles.


Myth Cycles is a nod to going against the grain, challenging common paradigms and misconceptions within the cycling industry—everything from steel bikes are too heavy to ride to the emphasis on racing weight to the very idea that bike builders should hide their trade craft secrets from the curious onlooker or prospective newcomer to bike building. The name is also about creating your own mythology, getting out and riding every chance that you get. You have to get out in order to tell a good story with your buddies over a cold beer and to tell a tall tale to your grandkids once your body refuses to climb into the saddle. “Our stories are all we really get in the end,” Tomczak says, “and they better be worth telling.”

Tomczak started his welding education and career with the intention of becoming a bike builder. In 2010 he graduated from welding school with an emphasis in TIG welding and CAD design, yet instead of going straight to building frames he wanted to gain a metalsmith’s approach to working with a variety of metals and design elements. He went to work for Ska Fabrication building assembly line products and de-palletizers for craft brewers, and he joined with the legendary tooling designer Ron Andrews of King Cage, building water bottle cages. Andrews developed his chops building custom parts for MIT, Fat City Cycles, Yeti and Intense Cycles among many others and provided a calculating Tomczak with a wealth of education.

It was the production environment, welding up to 500 water bottle cages per day, that shaped a strong desire in Tomczak to be efficient. It’s that same production mentality that now shapes his approach to bike building. “You begin to analyze each step of the process. Something will take me one minute twenty seconds to do and then you try and see if you can get it down to fifty seconds. If you can do that then over the course of a day it adds up to a ton of time,” he says.


It was during his workday that Tomczak also became efficient in capitalizing on Andrews’ knowledge from his days designing tooling and assembly fixtures. Tomczak was tenacious in learning assembly logic, weld sequencing, welding wire and tube diameters and how to build his own tooling and assembly fixtures for bike production. “I would ask questions and talk bike geometries until Ron would get so tired of it he’d leave the shop,” Tomczak laughs.

For the intrepid cyclists and those curious enough to consider building your own bike, Tomczak is pulling the stops and sharing his process in what it takes to build a custom frame. There are hundreds of steps to building a bike but he helped to narrow the process down to the essentials. There is not a lot of literature on bike building and a lot of bike builders are protective of their process, he says. He does recommend that you seek out a local bike builder to learn from or to even attend the United Bicycle Institute in Ashland or Portland, Oregon. Here’s to building what may become your favorite two-wheeled machine or… fostering a new-found respect for the difficult task bike builders everywhere take on to keep us happily rolling through the hills.


Step 1: Design

The most important step of the entire design process is deciding what you want out of your bike. This comes down to ride quality, where you will be riding your bike, what you want to carry, rider height and riding style and what frame material you will use. This is usually a long conversation with Tomczak’s customers and ends with a bike-fitter providing custom-tailor measurements.

This will dictate seat tube angle, chain stay length, head tube angle, top tube length, hub width and bottom bracket height. For those starting from scratch Tomczak advises starting with geometries from a bike that you already like.


His production frames are designed for versatility— slack head tube angle for stability downhill, steeper seat tube angle for long ascents, mid-length chain stays allow for agility and climbing and a higher bottom bracket height provide clearance and work well with a dropper post. This is his Wyvern production frame which, is designed for high country rides and longer mountain touring.

Materials: His favorite is air-hardening 4130 Chromoly available from Vari-Wall Tubing in Ohio. Air-hardening combined with double-butted tubing and a huge variety of tubing diameters and wall thicknesses allow for a custom tuned ride specific to rider weight, is very durable and is easy to repair. Steel provides a damp ride that absorbs vibrations well and snaps back in a controlled fashion unlike any other material. It’s the ‘feel of steel.’ Titanium is also another great option but requires even more skill to weld.

RattleCAD is a free CAD design program and BikeCAD Pro is a great tool.


Step 2: Preparation

Gather all of your raw materials together. This includes your top tube, down tube, drop-outs, brake tabs, seat tube, chain stays, seat stays, braze-ons, etc. Most tubes are sealed in plastic and are coated in oil to prevent rusting. In order to get a solid weld, the metal must be clean of any contaminants. Use a denatured alcohol and rag.


Step 3: Miter or Coping

In this step, you will cut the top tube, head tube and down tube in order to fit into place and provide a close tolerance fit at each tube junction. Use a magnetic angle finder to set the angle of your cut, this number is subtracted from 90 degrees and is derived from your CAD design. Secure each tube to be cut in a vice and use a hole saw to cut the tube. Tomczak uses a v-block style mill vice to keep everything secure. This is also when you will drill any bracket attachments for racks and for your bottle cages – doing so ensures that everything will be in plane. Deburr each cut and drilled hole with a metal file.



Step 4: Set the Jig

A jig or fixture to hold everything in place is essential to producing an end product that is straight and rides true. Tomczak built his own frame jig but they can be purchased starting at around $1300. Get your CAD drawing and set the bottom bracket height and seat tube angle. Dependent on bottom bracket width – road, mountain or fat bike – will determine the size “puck” required to hold your bottom bracket in place. Most road bikes are 68 mm wide, mountain are 73 mm and fat bikes are usually 100-120 mm. Make sure to orient your bottom bracket properly, advises Tomczak. Remember that one side is a reverse cut thread. Jigs can be purchased from Anvil Bikeworks or Henry James Bicycles to name a couple. You can find a great how-to for those wanting to attempt to build their own jig here.



Step 5: Welding

Test fit your top tube and down tube and chain stays to make sure that everything will align properly. After doing so tack weld the chain stays to the bottom bracket. After double checking that the chain stays are the appropriate length, you then can tack weld the dropouts on. Move on to tack welding the rest of the main triangle – top tube, head tube, down tube. Do not attach the seat stays yet.



Step 6: Check Alignment

Once everything has been tack welded pull the frame from the jig and using a ‘scratcher’ on an alignment table or a solid surface, you can ensure that the frame is straight and has not warped during the welding process. If anything has warped, Tomczak advises ‘cold-setting’ the frame and making any adjustment in alignment without adding heat. Heat will stress the metal and potentially weaken it. “The best thing you can do is make sure your angles are spot on before welding,” Tomczak says, “and by welding at least 95 percent of the frame in the frame jig.” A weld can pull and warp as it cools. Check that the head tube is parallel to the seat tube. Check that the head tube and the seat tube are perpendicular to the bottom bracket.


Step 7: Seat Stays

Place the frame back into the frame jig and finish weld the main triangle. Fit your seat stays. This measurement is established by measuring from axle centerline from the drop out location to the top of the tire. Dependent on what tire you want to run – 27.5 x 3 or 29 x 2.2 or 26 x 4.8, etc – will dictate where you bend the seat stay for tire clearance. Tack weld the stays into place. Pull the frame from the jig and finish weld the seat stays into place. Warping is not a concern here because the tube angles are triangulated and pulling or warping is uncommon.


Step 8: Install Brake Tabs, Cable Guides and Braze-Ons

Many bikes do not require brake tabs but install ‘em if you need them. Clamp braze-ons and cable guides into place and install the seat stay bridge at this point.


Step 9: Chase Threads

Using a Park Tool’s reaming and facing tool, ream the seat tube to remove any metal burrs, chase the threads in the bottom bracket and face the bottom bracket. Ream and face the head tube. This step insures that all surfaces are smooth and removes any warpage that may have occurred during the welding process. For specific tools and detailed process advice, check out this tutorial from Park Tool.

Step 10: Powder Coat or Paint

Tomczak powder coats his frames because it’s a durable paint choice that well last through the daily abuses of bike riding. An average powder coat is 3-5 mm thick and is hardened in an oven around 450 degrees Fahrenheit. You can also break out a rattle can for something that requires less specialized equipment but you’ll be frequently repainting your frame.



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