Fit On the Fly With Guru's Dynamic Fit Unit

If you choose a bike based on 10 test rides, you're likely choosing a bike based on the fit of each bike during the test ride, says J.T. Lyons, a bike fitter at Moment Cycle Sport in San Diego. Lyons spoke about bike fit and more at a breakout session during GOTRIbal's 2010 Conference and Retreat in San Diego.

A highlight of Lyons' session was a demo of a Guru Bikes' Dynamic Fit Unit (DFU), one of only eight units currently in North America. Moment Cycle Sport got their DFU second off the line.  

"We do fit before picking out the bike," says Lyons. "And the DFU has no limits. We look at the contact points between you and the bike--they need to be in the right orientation and each point will have its own comfort setting," says Lyons.

With a good aerodynamic position comes speed. During the session Lyons used the DFU to demonstrate the difference in a rider's position, fit and related aerodynamics on a road bike with clip-on aerobars versus a tri-specific bike. When you put aerobars on a road bike it gets squirrelly because the weight distribution is different from how the bike was designed to be ridden, he says. 

A week later and two thousand miles away I enjoyed a second DFU demo as part of SBR Coaching's open house in Verona, Wisconsin, as part of a new partnership between SBR Coaching and Training Center and Rocket Bicycle Studio.

Because bike fit is so critical to a rider's comfort and performance SBR Owner Jessica Laufenberg knew investing in a DFU was well worth its price tag and nearly year-long wait. "We put the order in at Interbike a year ago and it arrived two weeks ago," she says. "It was like looking at the box from the Indiana Jones movie," she says. "We opened it and took five minutes just to stare at it."

DFU Engineer and Creator Mathieu Fagnan was on site to answer technical questions about the DFU's development and purpose.

"It became clear we needed a tool to separate the position of a rider from the bike," says Fagnan. "So I looked at what defines a rider's position in space." Fagnan discovered that it's the relation of the crank, aerobars and seat.

The DFU allows the fitter to truly focus on the fit versus working around the geometry of a bike, he says. "From the rider's side it brings a raised level of confidence in the quality of the fit," says Fagnan. "With the fit unit, the rider will experience the exact position they'll have on the bike, and you can make adjustments while the rider is pedaling."

The bike fitter enters data into software during the fit and can record multiple fit sessions for a single rider's varying needs such as early- or late-season racing, TT racing or cyclocross.

"The DFU is fully and precisely adjustable. It moves to any position possible as you ride it," says Laufenberg. Due to computer-controlled precision stepper motors that are continuously adjusted in real time, cyclists can maintain form while they are pedaling. Laufenberg also says, "It's fully integrated with biomechanics and performance analysis software, so you can not only tell what optimum fit feels like--you can see what measurements give you the best results."

Overall the DFU allows fitters to fit on the fly--efficiently and precisely.

"With this system we can simulate any terrain and any bike geometry while measuring watts, power transfer for each foot--the works," says Peter Oyen, co-owner of Rocket Bicycle Studios. "It's invaluable information for athletes needing to fine-tune bike fit or order a custom frame."

Laufenberg emphasizes athletes can get a fit without buying a bike. SBR and Rocket Bicycle's goal, concept and mission are to educate athletes, not to move inventory. "We want you to be comfortable and riding your bike for the rest of your life," she says.  


Big Fit: 2010 Ford Ironman World Champion, Miranda Carfrae, switched from a 51 cm bike to a 47 cm frame after a bike fit from Mat Steinmetz of Retul ( Read more about Carfrae's fit with Steinmetz at

Sara Cox Landolt dreams of a perfect bike fit while writing from home. She is a married mom who depends on superior running technique to chase and catch her three sons. She's a USAT Level 1 certified coach with 15 years of triathlon experience. Her passion is encouraging first-time triathletes. Read her blog at

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