Part 4: How Dupli-Fit’s Direct Approach Compares to Traditional Bike Measurement Techniques
In Part 2 and Part 3 of this series, we outlined two different methods for defining the relative position of the three primary contact points that determine a rider’s fit: the saddle, handlebar, and bottom bracket (or pedal spindle). In this section, we’ll explore why Dupli-Fit’s direct point-to-point approach allows for faster and more accurate measurements compared to traditional fitting methods. By reducing the complexity of the workflow and minimizing opportunities for user error, Dupli-Fit not only saves time but also improves repeatability and precision.
1. Summary of Approaches
Traditional X-Y Measurement (Part 2):
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Uses horizontal (X) and vertical (Y) references to determine position.
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Tools: levels, plumb bobs, tape measures.
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Involves four steps: identify endpoints → reference to X/Y → calculate position → record measurement.
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Susceptible to interpretation errors and time-consuming setup.
Dupli-Fit System (Part 3):
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Measures directly from point-to-point (e.g., bottom bracket to saddle).
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Tools are designed for direct length and angle readings.
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Length and Angle are the primary measurements bike fitters make of the rider.
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Reduces steps from four to two, eliminating indirect calculations and reducing potential for error.
2. Evaluation Criteria for Bike Fit Measurement Tools
The three essential characteristics of an effective bike fit measurement system are:
A. Precisely Located Endpoints
B. Accurately Recorded Measurements
C. Uniquely Defined Endpoints in Space
Let’s compare both methods using these criteria with a focus on the critical Bottom Bracket to Saddle measurement:
A. Endpoint Location
Traditional Tools:
Require visual estimation (“eyeballing”) of contact points using general-purpose tools (e.g., plumb bob or tape measure). No standardized locator for endpoints.
Dupli-Fit:
Uses fixed references for high consistency:
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Bottom Bracket: features a retractable locator for precise alignment (see Fig. 1a).
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This ensures that endpoints are consistent across setups and bikes.
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Saddle: measured at the standardized 80 mm width - widely accepted as the sit bone reference. (see Fig. 1b)
B. Measurement Accuracy
Traditional Tools:
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Rely on visual alignment with references (e.g. bottom bracket, top of saddle) not directly in contact with the scale from which measurements will be taken. This often results in what is known as parallax error (Fig. 2a).
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Devices must be manually held parallel to the bike’s centerline, a challenge for accurate replication often resulting in misalignment error (Fig 2b)
Dupli-Fit:
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Measurements made with on-scale reference points to eliminate parallax errors, while scale rotation is controlled parallel to the bike centerline, eliminating misalignment (see Fig. 2c)
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The Dupli-Fit PRO model retains the Dupli-Fit’s advantage, with the added benefit of digital angle measurement with 0.05° resolution (Fig 3)
C. Practical Benefits of Dupli-Fit
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Speed & Efficiency:
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Fewer steps, less calculation, and integrated tools streamline the fitting process.
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Improved Accuracy:
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Built-in locators, minimized human error, and digital options ensure higher measurement precision.
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Repeatability Across Bikes:
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Ensures a consistent feel between bikes, which is essential for serious riders sensitive to small changes.
Data Compatibility:
While Dupli-Fit adopts a length-angle convention, a free app is available to:
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Convert X-Y data to length/angle.
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Chart and compare up to six bikes in either format.
Conclusion
Dupli-Fit outperforms traditional X-Y methods by improving endpoint precision, reducing measurement errors, and offering a faster, more accurate, and repeatable way to replicate bike fit. For riders who value performance and consistency, Dupli-Fit provides a superior solution—backed by data, enhanced by technology, and made accessible with a user-friendly conversion app allowing users to store and convert their existing X-Y data in polar coordinates, then graph up to six locations on their bike setup.