The pursuit of optimal cycling performance depends on a fundamental philosophical question regarding bike design. Which factor, lightweight or aerodynamic, holds greater significance?

Engineers and cyclists struggle with this age-old conundrum as they negotiate the fine balance between shedding kilos for hill slogs and ensuring the bike and rider are as slick as possible to give aerodynamics first priority on level ground.

The importance of aerodynamics increases as one moves faster. Conversely, a steeper gradient leads to more significant weight reductions during a climb.

There thus is a tipping point speed or gradient between the two where the balance moves from one to the other.

Usually, for expert riders, this tipping point is at a gradient of roughly 7.5%. Amateurs bike more slowly, hence the tipping point is also lower—usually at approximately 4.5%.

Aerodynamics has become more crucial than weight in most cycling conditions.

This is a great simplification, but there's much more to learn about how to prioritize these two elements to fit your riding style and even support your strategy in a bike race through your equipment selection. In this guide, we will explore the following topics.

Lightweight Vs Aero On Flat Terrain

Experienced aerodynamicist and engineer Jean-Paul Ballard co-founded Swiss Side, having spent more than 14 years in Formula One. He contributes a wealth of aerodynamic knowledge to cycling.


From speeds as low as 9 mph (15 km/h), aerodynamic drag is the main impediment a cyclist encounters, notes Ballard.


Generally speaking, lighter gear gives the most benefit on mountainous rides.

But what about riding an average of 16 mph (25 km/h) in a Gran Fondo or a hilly sportive? Which factor, weight or aerodynamics, holds greater significance?

Saying, "At 16 mph (25 km/h), aerodynamics clearly outweighs weight," Ballard insists in the supremacy of aerodynamics at this speed. Our sophisticated simulations at Swiss Side can show this.

Ballard offers a particular case study to support his argument:

Riding at an average speed of 16 mph (25 km/h), consider a simulation of a 75-mile (120 km) journey with 3,280 feet (1,000 meters) of elevation. An 80-kilogram cyclist on an 8-kilogram bike will typically produce around 150 W.

"Let's contrast the impact of a 5% aerodynamic improvement on the bike against a 5% weight loss in the bike. This is like deciding between a set of aero wheels and a light-weight set of climbing wheels.

In this case, then, which alternative saves more time?

Reducing weight by the same percentage saves only 20 seconds; reducing aerodynamic drag by 5% results in a time reduction of 3 minutes and 30 seconds.

Stated differently, aerodynamics are far more important to cyclists on generally level ground than weight reductions.

Lightweight Vs Aero On Climbs

Apart from mountain summit finishes or uphill time trials, an aerodynamic bike is nearly always the fastest choice across a whole course.

This remains true even when riding under the protection of the peloton, as the drag decrease still demonstrates significant value.

From a professional cyclist's standpoint, Ballard points out that on climbs with an average gradient of 7.5%, the tipping point when bike weight becomes more important than aerodynamics is.

Given their usually slower speeds, amateur riders have a lower threshold—about 4.5%.

These revelations, however, are only generalizations. Individuals vary in the specific gradients at which weight dominates aerodynamics.

However, the overall data indicates that a lightweight, less aerodynamic bike setup becomes useful only in uphill time trials or races that finish at a mountain.

The importance of bike weight is particularly significant during acceleration and on steep hills. Road riding often exaggerates its effects.

Why is this such a case? One concrete consideration is weight. Riding a bike straight away makes its weight clear. Many riders find this to be a regular experience.

By contrast, spotting an aerodynamic bike is more difficult. Evaluating aerodynamic efficiency calls for more advanced techniques, including computational fluid dynamics (CFD) software or wind tunnel testing.

Unlike weight, aerodynamics cannot be quickly assessed by merely grabbing a friend's bike before a ride.

What Are Aero Bikes?

The SystemSix is Cannondale’s flagship aero road bike. Credit: Cannondale

Aerodynamic bikes give minimum wind resistance top priority. Since 85% of the opposition a cyclist encounters is their own body, they want to be as efficient as possible.

Aerodynamic bikes can have a shorter head tube to minimize frontal profile and hence ease this resistance.

Aerodynamic bikes typically feature a longer frame reach, expressed horizontally from the center of the bottom bracket axle to the head tube, in addition to a shorter head tube. This reach offers understanding about the intended use of the bike.

Differentiating frame reach from rider reach is absolutely vital. Adjusting rider reach—the distance from the saddle tip to the handlebar center—requires either a longer stem or more saddle setback.

Aerodynamic bikes' aggressive geometry could be difficult for riders without the core strength or flexibility needed to keep the ideal posture.

Without the ability to gently acquire this decreased position, the aerodynamic benefits fade and the risk of injury increases.

Aerodynamic bikes also defy UCI rules with tube profiles that follow a 3:1 ratio—for every centimeter in depth, they can be up to three centimeters long.

These tubes, with their tapered leading edge and contoured tail, are meant to cut across the wind. The tube "tail" occasionally truncates, mimicking a sculpted tail in different wind angles.

These bikes feature distinct, angular, and aggressive frame shapes. Aerodynamic bikes sometimes have straight, flat top tubes, unlike the sloping top tubes seen in lightweight and endurance bikes for enhanced comfort.

This design lowers frontal profile and increases rigidity by cutting the distance from the seat tube connection to the seat.

Despite having the same geometry and specs, the additional material required for these aerodynamic designs typically makes these bikes heavier than their lightweight counterparts.

Although they are only authorized for time trial stages and not in ordinary racing, time trial bikes are the most aerodynamic of all.

Cycling enthusiasts may find the most graphic illustration on steep time trial stages, such as Stage 16 of the 2023 Tour de France.

Starting the stage on a time trial bike, Tadej Pogačar then underwent a frenetic, pre-planned swap to a lightweight road bike as the race ascended a significant hill.

Having said that, Pogačar was amazed by Vingegaard on the stage even though the Danish rider stayed with his time trial bike!

What Are Lightweight Bikes?

The Flyee Road Bike is ICAN's lightweight road bike

While maintaining a balance in performance characteristics, lightweight motorcycles aim to be as light as possible.

Usually chosen by general classification riders and team leaders, lightweight bikes balance the unique qualities of aero and endurance bikes in terms of comfort, stiffness, and handling.

Although they are not as comfortable as endurance bikes, they usually provide better comfort than aero bikes.

Despite their weight making them more agile, their handling is similar to aero bikes.

Lightweight bike designs center on thin tube profiles that strike a compromise between durability and stiffness without adding undue weight. This slimness absorbs road vibrations for a more seamless ride and permits some flexibility.

By means of particular carbon types or additional fiber layers, these bikes generally exhibit improved stiffness in crucial locations like the bottom bracket, seat tube, head tube, and chainstays, optimizing the balance between lightweight and strength.

Though their stiffness-to-weight ratio is more advantageous, lightweight bikes might not be as rigid as aero bikes.

With their larger tubing, aerobikes are heavier yet stiffer. With rather less weight, lightweight bikes manage to provide similar rigidity.

Depending on their model range, manufacturers of lightweight motorcycles vary in their geometry.

Some, who have distinct lines for aero, endurance, and lightweight bikes, may lean more aggressively towards their lightweight models. Others may provide a more laid-back geometry, particularly if their selection lacks a specific endurance bike.

The geometry of lightweight bikes, including current all-arounders, can vary greatly.

What Do The Pros Choose?

Professional cyclists sponsored by Cervélo, like Jumbo-Visma's Vingegaard, benefit from choosing their gear based on the race stage.

Emphasizing its focus on effectively cutting through the wind, Vingegaard rode the Cervélo S5, an aerodynamically designed road bike with characteristics reminiscent of the Cervélo P5 time trial bike, at the beginning of this year's Tour de France.

For high mountain stages, though, Vingegaard changed to the lightweight climbing bike, the Cervélo R5.

This bike veers toward a more classic design, stressing low weight and excellent stiffness for greater performance on lengthy climbs, even though it still incorporates aerodynamic components.

Though the stage as a whole may favor an aero bike, strategic concerns could see a pro cyclist choose a lightweight setup for climbing.

This is because, particularly on their steepest parts, the most pivotal moments of the race are likely to occur on climbs. Consequently, they might choose their tools to give performance in certain pivotal racing moments top priority rather than the stage as a whole.

If the race includes a summit finish, it is likely to take place on a mostly flat stage, with a significant climb (or numerous climbs) towards the conclusion.

Weight Vs Aerodynamics in Bike Wheels