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Brian Berthold

Brian Berthold, suspension engineer
Engineer, Downhill Racer, Musician

Brian spent the next 15 years as a professional race engineer, chassis designer, aerodynamicist and shock absorber design specialist.


His work has won many races and championships at the highest levels of motorsport, from Formula 1, to Indy Cars to Paris/Peking Rallye cars to LeMans prototype sports cars. He had worked for such factory teams as Jaguar, Audi, Nissan, Toyota as well as motor racing luminaries such as Jackie Stewart, Hans Stuck, Walter Rohrl, Arie Lyundyk, Chip Ganassi, Robby Gordon and many more.

The man who created Tantrum Cycles is relentlessly driven to improve things. Even as a kid, he was modifying bikes to go faster. Wheels, tires, gears, frames; it was mix and match with whatever worked. But with no money for college and the impending Vietnam era draft looming, Berthold chose to enlist in the Air Force. The GI Bill allowed him get a Mechanical Engineering degree and begin a colorful career in auto racing.


Throughout his high speed motorsports career, bikes were never far from Berthold’s focus. He was known in the pits for bringing whatever his latest creation was and riding it through the paddock, eschewing the common scooters and golf carts. Riding a bike around a race track provided subtle insights that helped Brian engineer the car. Things such as a slight, previously unnoticed elevation change or a bump, entering or exiting a corner.

When the mountain bike world started getting serious about suspension in the 90’s, Berthold knew he had something to offer.


While still employed full time in auto racing, Brian started racing XC and downhill and developed OE prototype shocks for Cannondale and Proflex. To address a growing demand for downhill specific products, he designed a highly regarded 7 inch travel upside down fork.


Brian sponsored a male and female pro DH racer, as well as traveling the NORBA National DH circuit himself, racing as an amateur while servicing customers and athletes.

Later on, first with his Brake Therapy disc brake conversion for the rear in high demand since no bikes had mounts on the frame, then with the Brake Therapy floating brakes, Brian had customers ranging from John Tomac’s factory team, to the Giant, Jamis and Trek factory DH teams as well as supplying floating brakes to Trek on an OE basis. He then starting working with and sponsoring Fabian Barel on the Kona factory DH team. This led to Brake Therapy having full factory sponsorship for the entire team, resulting in multiple World DH championships for Fabian and Tracey Mosely.

As he was already designing and licensing floating brakes to Kona, Berthold approached them with his concept for a Magic Link bike
. Just a plastic model at the time, but Kona gave Brian a Dawg to hack up and make a rideable prototype, which Brian promptly dubbed the “Frankendawg”. Less than a year later, the first production Magic Link Coilairs were in the hands of customers. Rushed to market, the first bikes suffered from early QC issues and were a bit ungainly to look at. Berthold remembers “my mandate was to adapt the invention into an existing Kona frame, changing as little as possible. The result was akin to stuffing a V8 into a Chevy Vega (ok a Prius).  

The bikes garnered worldwide critical success and were among the earliest models to sell out.


The line spread to 3 models with the G2 version, which was cleaner in every detail, with the shorter travel Abra Cadabra and 2+2 complimenting the big mountain Coilair. Said Berthold “the G2 bikes were a clean sheet of paper, which I really enjoyed designing and working with the factory to innovate new production methods to optimize the design for the Magic Link”  

The Magic Link bikes sold well over a 5 year period, garnering over US $40 million in sales and numerous glowing magazine reviews for its suspension performance. 

Brian knew he could design an even better system. A system with the Magic Link’s advantages of variable geometry and spring rate according to the demands of rider and terrain, but in a more simple layout, lighter, stiffer, easier and cheaper to make, easier to understand and setup and less visually intimidating due to the elimination of the secondary auxiliary shock.  

The Missing Link was born, with the added advantages of even more geometry change and the ability to go to infinite stiffness in the rear spring rate, if climbing dictated and smooth surface allowed.  

Brian decided to take a different route licensing this design. The exclusive arrangement was just that. It excluded too many brands and people that wanted to enjoy the design. Berthold decided the best way to make it available was to start his own brand. Using a wealth of connections and knowledge accumulated from the bike industry, he formed Tantrum Cycles not only to make the design available to customers, but to promote and license the design to other brands. This would increase the scope of availability. And no matter what the licensees might do, Brian knew that with Tantrum, he was free to offer the bike in whatever configuration he might choose.


For a pictorial of Brian's career go to

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