What Is an Aero Base Layer? (And Why It's Also Called an Aero Bra)
What Is an Aero Base Layer?
An aero base layer is a short-sleeved undergarment with raised ribs on the sleeves that reduce aerodynamic drag when worn beneath a skinsuit or jersey. The ribs sit under the outer fabric rather than on top of it, creating a macrostructure that trips the boundary layer of air flowing over your arms — shifting it from laminar to turbulent flow, and cutting drag as a result.
It's often called an aero bra, because of the cropped, close-fitting shape. Same garment, same technology, two names.
Rule 28 developed the original Aero Base Layer in 2019 and it's now worn by over half the WorldTour peloton, including men's and women's Tour de France champions. It is fully UCI approved.
How does an aero base layer actually work?
Most aero clothing works by adding texture to the outside of the garment. Ribbed and dimpled fabrics have been used successfully for years — they trigger turbulent airflow, which reduces pressure drag.
The problem is that surface texture comes with a cost: higher skin friction. You gain on one side of the equation and lose on the other.
An aero base layer takes a different approach. Instead of texturing the outer surface, it places a macrostructure underneath it. Our wind tunnel testing at the Silverstone Sports Engineering Hub showed that macrostructure on its own — exposed to the air — does very little. But placed beneath a surface layer, it shifts flow from laminar to turbulent and produces drag reductions significantly greater than traditional textured fabrics, without the same skin friction penalty.
In practice: the ribs subtly deform the smooth fabric sitting on top of them, and that deformation does the aerodynamic work.
Read the full Aero Base Layer test data →
Rib spacing determines the speed it works at
This is the part most people miss. An aero base layer isn't optimised for all speeds — rib spacing determines where it works best.
The rule of thumb: the higher the speed, the narrower the rib spacing needs to be.
That's why there are two versions:
The Aero Base Layer — optimised for 35–50 km/h. This covers the speeds most road racing and time trialling actually happens at, which makes it the right choice for the overwhelming majority of riders.
The High Speed Aero Base Layer — optimised for Track Sabove 50 km/h, with narrower rib spacing. Built for road sprinters, track racers and elite time triallists. Developed over five to six months from ten prototypes, tested at 50–75 km/h at two yaw angles to replicate velodrome conditions, with South African Olympic track cyclist Jean Spies — who then wore it at the Track World Championships.
If you're not regularly riding above 50 km/h, the standard Aero Base Layer is the faster option for you. Buying the high speed version won't make you quicker at road race speeds.
Read the High Speed Base Layer development data →
What should you wear it under?
The base layer needs a smooth surface layer above it to work against.
Works well under: skinsuits and jerseys with untextured, smooth fabric on the arms.
Works poorly under: sleeves that already use striped aero fabric — the two stripe patterns can interfere with each other and may even increase drag. Also thick winter jackets, where you're unlikely to see any benefit at all.
One honest caveat: it doesn't work equally well for everyone. Arm shape and riding position both affect the result. We have seen third party dats ahowing the high speed aero base layer has performed well at lower speeds on very small riders.
When you don't need a separate base layer at all
If you're buying a Neo suit, you don't need to buy an aero base layer separately.
Our Neo collection integrates the base layer technology directly into the suit's sleeves. That isn't just convenience — it's a more precise setup than a separate garment can achieve, because the rib structure and the surface fabric are engineered as a single system rather than two independent layers that have to interact correctly.
The Neo Suit testing data bears this out: the integrated-sleeve Neo Suit outperformed the previous-generation Neo Suit worn with a separate Aero Base Layer at every speed tested, and the gap widened with speed — from around 10W at 40 km/h to over 34W at 60 km/h.
So the decision is fairly simple:
Buy a separate Aero Base Layer if you already own a skinsuit or jersey with smooth sleeves and want to make it faster.
Buy a Neo suit if you're buying a new race garment and want the fastest available setup, with the technology built in.
Shop the integrated-sleeve range: Neo Road Race Suit → · Neo Time Trial Suit → · Neo Triathlon Suit →
Frequently asked questions
What is an aero base layer?
An aero base layer is a close-fitting undergarment with raised ribs on the sleeves that reduce aerodynamic drag when worn beneath a skinsuit or jersey. The ribs create a macrostructure that trips the boundary layer of airflow over the arms, shifting it from laminar to turbulent flow and reducing drag.
Is an aero bra the same as an aero base layer?
Yes. "Aero bra" is a common informal name for an aero base layer, used because of the cropped, close-fitting cut. They're the same garment with the same technology.
Are aero base layers UCI legal?
Yes. The Rule 28 Aero Base Layer is fully UCI approved and is worn in competition by over half of the WorldTour peloton.
Do aero base layers work under any jersey?
No. They work best under smooth or lightly textured sleeves. Under sleeves that already use striped aero fabric, the two patterns can interfere and may increase drag. They provide little benefit under thick winter jackets.
Which aero base layer should I buy?
The standard Aero Base Layer is optimised for 35–50 km/h, which covers most road racing and time trialling. The High Speed Aero Base Layer is optimised for above 50 km/h and is designed for road sprinters, track racers and elite time triallists.
Do I need an aero base layer with a Neo suit?
No. Neo suits integrate the base layer technology directly into the sleeves, in a more precisely engineered setup than a separate garment allows. In testing, the integrated Neo Suit outperformed the previous Neo Suit worn with a separate base layer at every speed.
All testing referenced conducted at the Silverstone Sports Engineering Hub. Individual aerodynamic results vary by rider, position and equipment.
