Aero Sock Testing – Benchmarking Rule 28 Against the Market

Key finding: In independent wind tunnel testing (ATP Performance, Silverstone Sports Engineering Hub, 25 March 2025), the Rule 28 One Aero Sock delivered the best overall performance of any sock tested across most speeds, saving up to 4.07W at 40 km/h and 3.36W at 50 km/h compared to a standard (non-aero) cycling sock.

Power saved vs. a generic cycling sock, by speed (positive = faster)

Full results across all five tested speeds (30–50 km/h) below.

Aero socks are the first piece of kit you should consider upgrading when it comes to buying performance. In terms of cost per watt saved, they typically offer the best return on investment compared to other performance-enhancing options, such as clothing, bikes, or chains. More on this here.

There are now several brands offering aero socks. Some use the same materials, while others employ unique fabrics in an attempt to unlock performance advantages or to stand out visually.

Previously, we tested our One Aero Socks against our older generation of aero socks and observed an impressive performance gain (that test can be found here) — enough, we felt, to justify the significantly increased material cost. But how do they compare to the rest of the market? To find out, we selected a range of the most popular and performance-focused aero socks available and put them to the test.

Important Disclaimers

1. Individual Variability

This test was conducted on a single rider. The performance of kit, as well as other cycling equipment, can vary between individuals. From our experience, trends in sock performance tend to remain fairly consistent — i.e. the best-performing sock on one person is generally the best-performing on another — but the actual watts saved will vary.

Previously, we have seen greater savings from aero socks than we did in this test, even when testing the same products. This highlights an important point: individual results may differ.

2. Performance Changes with Speed

Performance varies with speed. As shown in the data, it is not possible to extrapolate performance at low speeds to predict performance at higher speeds.

The Test

Location & Date

• Venue: Silverstone Sports Engineering Hub Wind Tunnel, UK
• Date: 25th March 2025
• Conducted by: ATP Performance, an independent aerodynamics and cycling performance consultancy

Although the testing was funded by Rule 28, ATP Performance managed all data collection, setup, and methodology independently. We strive for full transparency and unbiased reporting. To reinforce this, all products tested have been donated to SSEH and are available for independent verification by everyone visiting.

Test Setup

• Rider: Rowan Baker, professional rider for Raptor Factory Racing
• Bike: Raptor RL1
• Position: A stable and repeatable position, maintained comfortably for the duration of each test
• Monitoring: Multiple camera angles (side, front, and top) and edge outlines ensured consistency across runs
• Cadence: Held constant for all test runs
• Calibration: The system was pre-tared and calibrated before each run

Testing Protocol

• Each pair of socks was brand new prior to testing.
• Tests were conducted at speeds ranging from 30–50 km/h, in 5 km/h increments, reflecting most real-world rider speeds.
• Each test run lasted 30 seconds.
• Yaw angle: 0 degrees (to eliminate crosswind effects and focus solely on product performance).

Socks Tested

• Rule 28 Pro Sock (Baseline – standard sock)

• Rule 28 Aero Ish Sock (Aero pattern on a standard sock)

• Rule 28 One Aero Sock

• Competitor Spatz

• Competitor Castelli

• Competitor Nopinz

• Competitor Sockeloen

• Competitor Aero Cycling Gear

• Rule 28 Prototype

Results & Data

Power required (Watts) to maintain a set speed with each set of aero socks

Difference in power required (Watts) Vs. a non-aero sock (Rule 28 Pro Sock) 
negative numbers indicate worse performance

Key Findings

4.07W saved at 40 km/h, 3.36W at 50 km/h — the Rule 28 One Aero Socks delivered the best overall performance of any sock tested, most notably at 40–50 km/h race speeds, against the baseline Rule 28 Pro Sock.

Up to 3.28W saved at 40 km/h — the Rule 28 Prototype matched or slightly beat the One Aero Socks at 30–40 km/h, though its advantage declined at 45–50 km/h.

+1.57W at 30 km/h, −3.60W at 45 km/h — Castelli was the strongest non-Rule 28 sock at low speed but lost its advantage as speed increased.

−11.19W at 50 km/h — Aero Cycling Gear and Spatz had the highest power demands of any sock tested, making them the least aerodynamically efficient in this test. Both use smooth or dimpled fabric rather than the textured/striped fabric common to the other aero socks tested.

−9.23W at 50 km/h — the Rule 28 Aero-Ish Socks showed slight savings at most speeds but a sharp power increase at 50 km/h, its one weak point in the test.

Competitor performance varied significantly across the field — some competitor socks underperformed even the non-aero Rule 28 baseline at most speeds tested.

Final Takeaways

• The Rule 28 One Aero Socks emerged as a top performer, demonstrating consistent power savings across all speeds.
• The Rule 28 Prototype showed promise, particularly at lower speeds, though further refinement may be needed for higher-speed efficiency.
• Not all aero socks are created equal — some brands delivered significantly poorer performance, reinforcing the need for thorough testing before purchase.
• Performance benefits depend on speed — extrapolating results across different speeds is not reliable, as seen in the variation between 30 km/h and 50 km/h results.

For riders looking for the best balance of performance and efficiency, the Rule 28 One Aero Socks offer one of the most effective options in this test.

"All testing was done maintaining the same position throughout, all runs were pre-tared and calibrated, every other element remained constant... Obviously variable from person to person but generally socks are a bit more uniform in how they test than say suits." — Andy Turner, Head of ATP Performance