Tech Support: Shape Shifter

  • By Aaron Hersh
  • Published Dec 20, 2011

The motorized, computer-controlled Guru DFU, which stands for “dynamic fit unit,” can help you dial in your ideal fit.

The premier triathlon bike fit school and philosophy, F.I.S.T., teaches fitters to identify a rider’s preferred position by switching between potential configurations to help the rider perceive subtle differences. Mechanical fit bikes can create just about any position, but the rider often has to stop pedaling—or even dismount—while the fitter makes adjustments. These frequent interruptions make it difficult to perceive small differences, especially for novice riders. The DFU eliminates that problem. Here’s how:

• The DFU uses electronic motors to change saddle and aerobar position while the cyclist pedals. This allows the rider to feel the difference between potential frame and bike geometries without jumping off the bike then trying to recall the previous position after remounting.

• If you are deciding between a stock Guru, a Trek and a Felt, the DFU can mimic the precise fit coordinates so you can feel the differences between the actual, physical bikes. It can also take an aerobar attachment system into account, whether a bike uses a traditional stem or a proprietary integrated unit.

• In addition to its unique attributes, the DFU has all the features typically found on mechanic fit bikes. Saddles and aerobars can be swapped and the bike can be mounted with an adjustable-length crank and a Computrainer to measure power, cadence and pedal stroke efficiency.

Add Motion Capture

The DFU doesn’t measure rider position, only fit dimensions. Simultaneously using a motion capture system, such as Retül or Dartfish, quantifies the changes to the rider’s body position created by changes to the bike’s fit.

FILED UNDER: Gear & Tech TAGS: /

Aaron Hersh

Aaron Hersh

Aaron Hersh is the Senior Tech Editor of Triathlete magazine. To submit a question, write Aaron at

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