Date: March 2026

Subject: Mechanical Efficiency and Drag Isolation of the e*thirteen Sidekick 2.0 Hub vs some key competitors

  Target Audience: Mechanical Engineers, Industry Professionals, and the Performance Cycling Public

1. Abstract

Bicycle drivetrain efficiency is traditionally measured by parasitic loss while pedaling. Freewheeling drag (coasting resistance) represents a significant opportunity for "marginal gains," particularly in gravity-oriented or technical disciplines. This paper details a comparative study using a custom-built precision spin-down stand to measure the drag torque () of several industry-leading MTB hubs. Results demonstrate that the e*thirteen Sidekick 2.0 provides a statistically significant reduction in drag compared to competitors, most notably the DT Swiss™ 350 DEG. 

Sidekick achieved a 51% reduction in total system drag in a complete wheel test, and an 88% reduction in an isolated freehub drag test compared to its primary kickback-reducing competitor.

2. Introduction

Historically, mountain bike hub development has prioritized rapid freewheel engagement and minimal weight as the primary metrics of performance. However, these mechanical solutions often introduce parasitic drag as a byproduct. The e*thirteen Sidekick 2.0 was engineered with a patented freehub mechanism designed to decouple the freehub during coasting and add a fixed deadband during suspension actuation and chain movement. This freehub also theoretically minimizes internal friction while coasting. To validate these claims, we developed a "Fixed-Interval" spin-down test to quantify energy loss. This methodology isolates bearing, seal, and ratchet friction, providing a clear comparison of hub coasting efficiency between different manufacturers' products.

3. Apparatus and Methodology

3.1 Test Stand

• The test apparatus is constructed from a rigid 80/20 aluminum extrusion frame with a steel wheel support frame attached.
• Axle Interface: A standard 12mm thru-axle is used, threaded into a UDH derailleur hanger mounted to the frame.
• Preload Control: The thru-axle was torqued to exactly 8 N-m for every trial to ensure consistent bearing contact and seal compression.
• Data Acquisition (DAQ): An Arduino-based system captures timing data via a 12-point tone wheel (30° resolution) detected by an inductive sensor.
• For Hub-only testing, steel screws were installed at 12 regular points on the 15lb weight.

3.2 Environmental and Mechanical Controls

• Thermal Consistency: Tests were conducted at 68°F (20°C) to maintain consistent grease viscosity.
• Break-in Procedure: Hubs underwent a standardized break-in. An axle was installed in each hub, tightened to 12Nm, and spun for 5 minutes using a 1500 RPM hand drill to settle factory grease and seat seals.
• Trial Density: Each hub was subjected to three consecutive runs; results represent the mean of these trials.
• Competitor Hubs were purchased from an online retail channel in aftermarket packaging.

3.3 Hub-Only "System Simulation" Testing

To isolate internal mechanical drag from aerodynamic variables while simulating a coasting wheel, a 15 lb (33kg) rubber weighted plate (450mm diameter) was attached directly to the disc brake tabs of an unlaced hub.

• Dominant Inertia: The plate's Mass Moment of Inertia (MMOI) was calculated at , allowing for high-resolution measurement of drag torque .
• The mass and moment of inertia of each hub was neglected for the purposes of this test, as all hubs tested weighed between 280g and 350g, so the moment of inertia of the plate dominates the small contribution from each hub.
• Fixed-Interval Window: The DAQ begins recording at 80 RPM and stops at 20 RPM.

Two specific test modes were utilized:

• Freewheeling Simulation (Hub Shell Turning): The 15lb weight is attached to the hub shell (via disc tabs) while the freehub body is held stationary. This simulates a bicycle wheel coasting, where the hub shell and its bearings are rotating relative to a fixed drivetrain.
• All-Bearing Drag (No Ratchet): The hub is spun such that there is no relative motion between the freehub and the shell. This test bypasses the ratchet mechanism to isolate the rolling resistance of all internal bearings and endcap seals. This is a loose analog to the rolling resistance of the hub during pedaling.

3.4 Complete Wheel System Test

This configuration evaluates the hub as part of a complete wheel assembly Unlike the isolated hub tests; this mode captures the total system resistance encountered during on-trail coasting. For this test, the wheel is spun up and the freehub body is held stationary.

When the freehub is ratcheting in this configuration:

• Active Components: The drive-mechanism (ratchet/pawls) is actively ratcheting due to the relative velocity between the two bodies.
• Bearing Rotation: The primary hub shell bearings are rotating; freehub bearings are stationary.
• Seal Drag: Only the non-drive-side endcap seal and freehub-to-hub-shell seal are active.
• System Inertia: The Mass Moment of Inertia () of the hub shell rim, spokes, and nipples is calculated using the period of oscillation from a trifilar pendulum.

4. Discussion of Test Limitations

• No-Load Condition: These results reflect a "zero-load" state (or in the case of the weight, a nearly no-load condition). While this does not account for radial rider load, it serves as a sensitive baseline for bearing, seal, and ratchet efficiency.
• Aerodynamic Residuals: For Hub-only testing, aerodynamic drag is minimized by the plate's profile but not eliminated. For complete wheel testing, the aero drag coefficient is similar between wheels. However, since aerodynamic drag accumulates more as test duration increases, it actually "punishes" more efficient hubs (which spin longer), making our findings regarding the Sidekick's efficiency conservative for that test.
• Grease Temperature: Some drift in timed results was observed as consecutive tests were performed. This was attributed to bearing grease warming over consecutive runs. If a large discrepancy was observed, additional runs were measured, and the first run discarded, until consistent results were achieved for 3 consecutive runs.
• Axial Preload Sensitivity: While a standardized 8 N-m torque was used for the thru-axle, different bearing architectures (e.g., angular contact vs. radial deep groove) may respond differently to axial loading. This test does not account for the efficiency changes that might occur under variable thru-axle setups.
• Break-in: A cursory break-in was performed on each hub. This break-in did appear to make a difference in the test hubs, as measured by tests before and after break-in. It is reasonable to assume that further break-in could improve the results of some of the hubs tested, but the broad conclusions should stand.

5. Results & Analysis

5.1 Test A: Freewheeling Drag (Hub Shell Rotating)

This test simulates the resistance a rider feels while coasting. The 15lb mass is attached to the hub shell, and the freehub is held stationary.

Longer Spin Down Time = Lower Drag Torque / Torque values expressed in mN·m = milli-Newton·meters

5.2 Test B: All-Bearing Drag (No Ratcheting)

This test evaluates the baseline quality of the bearings and seals when the drive mechanism is bypassed.

5.3 Complete Wheel System Test

To simulate real-world usage, tests were performed on fully assembled wheels.

5.4 Data Variance and Technical Scope

Friction in rotating assemblies is subject to variations in grease distribution, seal elasticity, and manufacturing tolerances. Furthermore, every hub in this test would undergo significant break-in over hundreds of miles of riding, which cannot be fully replicated by an accelerated drill break-in. The data presented here is intended to draw a broad comparative conclusion regarding hub ratchet designs. While absolute numbers may vary across different testing environments, the relative performance delta between the e*thirteen Sidekick 2.0 and its competitors is robust and serves as a reliable indicator of mechanical efficiency.

6. Real-World Application: Calculated Power Dissipation (Watts)

At a coasting speed of 30 km/h (approx. 240 RPM or 25.13 rad/s for a 29" wheel), the mechanical power dissipated by the hub during freewheeling is estimated at:

The "Marginal Gain": The 1.37 Watt difference between the Sidekick and the DT Swiss™ DEG represents energy lost constantly while coasting. Over a long technical descent, this cumulative loss saps potential energy and reduces conserved speed.

7. Conclusion

The e*thirteen Sidekick 2.0 achieves an 88.5% reduction in freewheeling drag compared to the DT Swiss™ 350 DEG DF. By successfully decoupling the drive mechanism during coasting, it achieves the lowest in its class. Competitors attempt to solve pedal kickback but do so at a significant cost to mechanical efficiency. The Sidekick 2.0 is the current benchmark for high-efficiency, momentum-preserving hub design.

8. Appendix: Experimental Setup & Instrumentation

8.1 Precision Spin-Down Stand

8.2 Hub-Only Test Configuration

8.3 Complete Wheel Test Setup

8.4 Trifilar Pendulum Calibration

8.5 Data Acquisition Hardware

9. Trademarks and Disclaimers

• DT Swiss, 350, DEG™, and DF™, are trademarks of DT Swiss AG.
• Hope™ and Pro 5™ are trademarks of Hope Technology Ltd.
• RaceFace™ and Vault™ are trademarks of Fox Factory Holding Corp.
• Industry Nine™, I9, and Hydra™ are trademarks of Industry Nine, Inc.
• e*thirteen and Sidekick are trademarks of The Hive Global, Incorporated.

All trademarks, service marks, and company names mentioned in this document are the property of their respective owners. These products were chosen specifically as the primary high-performance market competitors to the Sidekick hub. All trademarks are used in this document for comparative and informational purposes only and do not imply any affiliation with, sponsorship, or endorsement by the respective trademark owners.