80% of the aero drag is caused by the rider, so anything you can do to drop the frontal area and make you more aerodynamically efficient will improve your performance more than changes to the bike. The Aero Position is the main reason triathlon bikes look the way they do ( apart from the fact that it looks cool!)
There are two key ways that you can improve your aerodynamics.
How aerodynamics affects cyclists
According to Aerocoach, unto 80% of the drag that a cyclist encounters comes from the rider, with only 20% coming from the bike, and the bigger you are, the more you cause the drag when you are cycling, but what is drag and why does it matter?
A bit of a drag!
There are two ways that airflow, whether it’s windy or driven by your speed, affects the speed of a body through the air.
- Air pressure drag – this is caused by the shape of the body as it moves through the air and it similar to the effect of a wing in provides lift, because it relates to the differential pressure between one part of the body and the other.
- Friction. Air passing over the skin of a body exerts a limited frictional force in the same way that the ground does on the tyres, but it’s very small compared with the other forces acting on the bike.
Air pressure drag.
As a bike moves, it pushes the air out of the way, and in doing so, creates a high-pressure zone at the front and a low-pressure zone at the back and the difference in pressure acts like a vacuum and pulls the bike backwards, slowing it down slightly.
This happens on all parts of the bike to a greater or lesser extent, so anything that you can do to minimise the frontal area of the bike or help the airflow at the back will help to reduce this.
Bike manufacturers will offer a Kamtail shaped frame ( basically a teardrop with the sharp bike cut off), deeper section wheels, internally routed cables and installing brakes out of the way all of which will reduce the drag of the bike, making it more aerodynamically efficient, and requiring less energy to achieve the same performance at speed.
The smaller the area that you present to the wind the less of a braking effect you get, and this is why you see a cyclist get as low as they can over the front of the bike, which allows them to present the smallest area to the wind without reducing the efficiency of their legs.
Tri Bikes take this to the extreme, with bar extensions and pads near the centre line of the bike to allow them to maintain a low position with the elbows inboard for long periods and pushes the hips forward which reduces the utilisation of the hamstrings during the cycle.
Riding in the drops and keeping the shoulders low at high speeds will allow you to achieve a similar effect.
Tight lycra is common on cyclists and I think we can all agree it’s not for aesthetic purposes!! Keeping clothes tight to the body and using smooth materials reduces drag and helps you go faster.
A few things to remember
Aerodynamic efficiency is a critical determinant of ultimate performance, and you should do as much as you can to reduce the drag you and your bike cause when riding, but whether you need to go to the extremes is a matter of opinion, cost and personal circumstances.
- It’s not your position that will determine your aerodynamic performance in a race, it’s how long you can maintain that position for. You see a lot of people with aero bikes racing out of the aero position, which means all they are doing is adding weight. You need to find the most aero position that’s comfortable for you.
- Aerodynamic effects are dependent on speed, and the air pressure drag only really kicks in above 25kmph, so unless you are operating consistently above this level aerodynamics are less relevant.
- Aero adds weight, so if you spend a lot of time on climbs, there will be a net negative effect on a more aero but heavier bike.