The Science of Aero Skinsuits: How a Skinsuit Saves You Precious Watts

In cycling, every watt is precious. Professional riders spend tens of thousands of dollars on the lightest frames and most aerodynamic wheelsets, yet many overlook one of the highest-return equipment upgrades available—the aero skinsuit. Wind tunnel testing data consistently shows that switching from a traditional jersey-and-bib-shorts combination to an aero skinsuit can save 8-15 watts at 40 km/h, equivalent to the aerodynamic benefit gained from spending tens of thousands on carbon wheelset upgrades.

What is an Aero Skinsuit?

An aero skinsuit is a one-piece design that combines the jersey and bib shorts into a single garment, eliminating the waist seam and overlapping fabric areas. Modern skinsuits typically feature the following:

• One-piece construction: The upper and lower body are connected, with no waist belt or elastic band.
• Aero fabrics: Wind tunnel-tested textured fabrics are used in key areas such as the arms, shoulders, and back.
• Extreme fit: Tighter than a Race Fit jersey, with virtually no excess fabric when worn.
• Aero cuffs: The cuffs typically use silicone grippers or elastic hems to ensure the sleeve ends lie flat against the arms.
• Short or half zipper: Compared to the full-length zipper of traditional jerseys, skinsuits usually employ a shorter zipper to reduce frontal air disturbance.

Aerodynamic Principles Explained

Why Does Clothing Create Air Resistance?

As air flows over a rider’s body, any irregularity on the clothing surface causes air disturbance, increasing pressure drag and friction drag. Specific sources of drag include:

1. Fabric wrinkles: Loose fabric flapping in the wind creates additional frontal area and turbulence.
2. Seam protrusions: The junction between jersey and bib shorts, zippers, pocket edges, and other stitching are all sources of air disturbance.
3. Waist elastic bands: The waistband of traditional bib shorts acts like a small fence at high speeds, blocking smooth airflow.
4. Fabric surface roughness: Different fabric surface textures have vastly different effects on airflow.

How Does a Skinsuit Reduce Air Resistance?

Eliminating seam interference: The most direct advantage of a skinsuit is eliminating the jersey-bib shorts junction at the waist. Wind tunnel tests show that merely removing this seam saves 2-4 watts at 40 km/h. This may seem small, but in a 40 km time trial, the accumulated time difference can reach 20-40 seconds.

Optimizing surface texture: Premium skinsuits use different fabric textures on different body areas. The outer arms typically use dimpled textured fabric (similar to a golf ball surface)—this seemingly rough surface actually reduces overall drag. The principle is that moderate surface roughness triggers the boundary layer to transition from laminar to turbulent flow, causing airflow to separate later, reducing the wake region, and thereby lowering pressure drag.

Compression fit effect: The highly elastic compression fabric of a skinsuit eliminates nearly all fabric flapping, making the body surface as close to a smooth, streamlined shape as possible. Research shows that eliminating fabric flapping can reduce overall aerodynamic drag by approximately 3-5%.

Wind Tunnel Data Evidence

Multiple independent wind tunnel tests provide quantitative data on skinsuit benefits:

Specialized Wind Tunnel Testing (2022)

In tests at the Morgan Hill wind tunnel facility, the same rider wearing different equipment was compared at 45 km/h and 0° yaw angle:

Equipment Combination	CdA (m²)	Relative Power Difference
Loose training kit	0.268	Baseline
Race Fit jersey + bib shorts	0.245	-12 W
Entry-level skinsuit	0.238	-16 W
Premium aero skinsuit	0.232	-19 W

Swiss Side Testing (2023)

Swiss aerodynamic research firm Swiss Side’s testing was more granular, comparing five different grades of skinsuits and finding a difference of up to 8 watts between the best and worst performers (at 45 km/h). This means not all skinsuits are equally effective—fabric selection and precision of tailoring are critical.

Real-World Validation

During the 2019 Tour de France time trials, riders of the Ineos team (then Team Sky) wore custom Castelli skinsuits, with wind tunnel data showing savings of approximately 7-12 watts compared to standard race kit combinations. Over a 27 km time trial, this equates to roughly 15-30 seconds of time advantage.

Different Types of Skinsuits

1. Time Trial Specific (TT Skinsuit)

This is the most extreme aero design, typically featuring full-body compression, a half zipper (or no zipper), and no pockets. The fabrics are optimized for the specific time trial position (extremely low drag, elbows on aerobars). Not suitable for general road racing due to the lack of pockets and poorer ventilation.

Representative products: Castelli Body Paint 4.x, Endura D2Z Encapsulator, Vorteq TT Suit.

2. Road Race Type (Road Race Skinsuit)

This is the most popular category in recent years, combining the aerodynamic advantages of a skinsuit with the practical features of a traditional jersey. Typically features: rear pockets (for carrying supplies), a full-length zipper (for easy on/off and ventilation adjustment), and better breathability. The wearing feel is close to a high-end Race Fit jersey, but with the added one-piece aerodynamic benefit.

Representative products: Castelli Sanremo series, Assos EQUIPE RS Aero Skinsuit, Rapha Pro Team Aerosuit.

3. Triathlon Type (Triathlon Suit)

Designed specifically for triathlon, needing to accommodate swimming, cycling, and running. Fabrics dry quickly, the pad is thinner (to avoid discomfort while running), and it features a front-opening zipper (for quick transitions).

4. Track Type (Track Skinsuit)

Track skinsuits represent the pinnacle of aerodynamic design. No pockets, no zipper (pullover style), and fabrics are fully optimized for the speed range of track racing (45-70 km/h). Every national team invests significant resources in developing dedicated track skinsuits before the Olympics.

Fit and Sizing Considerations

Key Sizing Factors

Sizing for a skinsuit is even more critical than for a regular jersey, as any excess fabric directly impacts aerodynamic performance:

• Size down: Many brands recommend choosing a skinsuit one size smaller than your regular jersey. It may feel extremely tight on first wear, but this is normal—in the riding position, the skinsuit stretches to achieve optimal fit.
• The arms are key: The cuffs should fit snugly around the arms with no wrinkles. The arms are the area where a skinsuit provides the greatest aerodynamic benefit.
• Shoulder mobility: Ensure there is still adequate room for shoulder movement in the drops position. Shoulders that are too tight will restrict breathing and bike handling.

Wearing Tips

1. Start from the lower body: Put your legs in first, adjust the bib short section, and ensure the pad is centered.
2. Smooth out the back: When pulling up the upper body, ensure the back fabric lies flat without wrinkles.
3. Adjust cuffs last: Confirm the grippers on the cuffs fit properly against your arms.
4. Check in riding position: Once on the bike, simulate your riding position and check for any obvious fabric bunching.

Heat Management and Comfort Considerations

The high degree of fit in a skinsuit means heat dissipation is typically inferior to that of a looser jersey. In hot weather above 30°C, wearing a closed skinsuit may cause overheating issues. Solutions:

• Choose a road race skinsuit: The full-length zipper can be opened for ventilation when climbing.
• Pay attention to breathable fabric zones: Quality skinsuits use highly breathable fabrics on the back and sides.
• Adjust hydration strategy: Your body’s cooling efficiency is lower in a skinsuit, so you need to be more proactive about fluid intake.

Return on Investment Analysis

A premium skinsuit costs approximately NT$6,000-12,000. In comparison, a carbon wheelset upgrade that provides equivalent aerodynamic benefit (10-15 watts) could cost NT$50,000-100,000. From a return on investment perspective, a skinsuit may be the most cost-effective aero upgrade you can make.

Of course, a skinsuit is not a magic bullet. The overall benefit of proper riding position, sensible power output strategy, and appropriate equipment configuration (helmet, wheels) far exceeds the change of any single piece of equipment. But if you are seriously pursuing performance, a good skinsuit is definitely worth adding to your equipment arsenal.

Related Reading

• The Science of Cycling Apparel: How Many Watts Can an Aero Skinsuit Really Save?
• Short-Sleeve Jersey vs. One-Piece Suit: Aerodynamic Benefits and Riding Experience
• Cycling Jersey Buying Guide: Functional Differences Between Aero Jerseys and Casual Jerseys
• Aero Time Trial Helmet Buying Guide: From Wind Tunnel Data to Real-World Selection