Cyclist
How to get more aero on your bike
Cycling is obsessed with aerodynamics. From crazy helmets to specially designed road bikes, every piece of performance kit is made with aero in mind, but despite that, it’s the rider that makes the most difference to aerodynamic drag when riding a bike.
How does aerodynamic drag work, and why should we care?
‘Aerodynamics is basically a measure of how much energy it takes to move through the air at a certain speed,’ explains Jamie Lowden, performance engineer at WattShop. ‘In becoming more aero you can either move at the same speed but for less effort, or go faster for the same effort.’
However, getting aero isn’t always the be all and end all, says director of AeroCoach, Dr Xavier Disley.
‘Aerodynamic drag kicks in above a specific speed and the proportion of the resistive forces that are slowing you down increases the faster you go. So if you’re travelling at less than 25kmh you are better off getting comfortable and sitting upright – and this is what we tell WorldTour time-trial riders.
‘The tipping point is somewhere around 25-27kmh, below which sitting up and getting more comfortable will likely mean getting more power out.’
So what impact does aerodynamics have above those speeds?
‘If you’re riding at around 30kmh then approximately 120 watts of what you are putting out is going into getting through the air,’ says Lowden.
‘If you could hold a more aerodynamic position, and get 10% more aero, then you’re going to save about 10 watts. And the impact increases with higher speeds.
‘If you’re freewheeling at 60kmh and go from sat right up on the bars to a super-tuck position, you are going to increase your speed to more than 70kmh.’ And it gets better for the competitive group riders among us.
‘The more aero you become the more difficult it becomes for someone to sit on your wheel,’ says Disley. ‘Not only does an aero body position help you go quicker, it also provides a penalty for riders sitting on your wheel.’
The reason for this is that adopting a more aero position means creating a smaller frontal area – the total shape you present to the wind. The smaller you are, the smaller the drag, but simultaneously the smaller the hole you ‘punch’ through the air for a rider on your wheel. Consider the difference between drafting a lorry versus a drafting a hatchback.
What is the most important factor for getting more aero?
‘You can buy yourself a fancy bike but as a rider you’re creating four times more aero drag than the bike is, so ensuring that you’re aerodynamic and holding a good position is key to minimising drag,’ says Disley.
‘Your body and your position on the bike accounts for roughly 80% of your aerodynamic drag. To reduce your drag from a positional perspective, it is often a case of a lower torso angle. When speed is high, get lower on the bike by using the drops, or adopt a breakaway position where you hold your hoods but have your forearms parallel to the floor.’
But what is an aero position?
‘Your head should be down and in line with the body, and generally you should roll your shoulders forward and up and tuck your head underneath,’ says Lowden. ‘On a drop handlebar, hold your bars so your hands are a bit narrower, or get narrower handlebars.’
Your speed is also affected by your arm position, which can dictate the position of you head and back. Holding the tops on the hoods and making a 90-degree bend in the arms may create a flatter back shape than reaching down to the drops with straight arms.
So kit doesn’t matter then?
It absolutely does. While body position will have the biggest effect, ‘flappy clothing will slow you down,’ says Disley. ‘It’s very difficult to be aero if your clothing is acting as a parachute. Tight-fitting clothing is a real win and has a big impact on how the airflow moves over your body.
‘For example, wearing a tight winter jacket rather than a flappy one will make a difference.’ But that doesn’t mean we all need skinsuits, says Lowden. ‘A well-fitting jersey with tight sleeves will have a positive impact.’
OK, I want to spend money, but not that much money. What’s the best value aero upgrade?
As our experts say, it’s widely accepted that the most effective piece of kit for a rider is a skinsuit, which depending on who you listen to can save around 15W at 35kmh – double what a set of wheels can save and triple what an aero helmet can save (though it must be said these are entirely product-dependent in that the gains are dependent on the kit itself and the components they’re contrasted with).
However, stems are an oft-overlooked place to gain speed. ‘A one-centimetre longer stem could help lower your torso angle significantly,’ says Disley, noting another area to gain speed you might not think of. ‘But flexibility to bend is key – tight hamstrings can severely limit your ability to pivot forward, for example, so something as simple and cheap as morning yoga classes can help you get much faster on a bike. ’
Can you ever be too aero?
‘You always need to make sure that you’ve got reasonable visibility,’ warns Lowden. ‘It’s really easy to put yourself in a position where your head is super-low, you’re looking down and you can’t see where you are going.’
It’s also importance to strike a balance, says Disley. ‘Aero is bad if it affects your ability to produce power. When we talk about that tipping point of 25kmh we’re assuming your more aggressive position isn’t causing you to lose more than the watts than you’re gaining.
‘Some people have the flexibility to hold a more aggressive position, but for lots of people their power tends to drop. In this case, hold the more aggressive position at higher speeds, rather than all the way down to 25kmh.’
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