Body Position and Aerodynamics on a Bike
Aerodynamics has really dominated the talk of bike tech for the last decade or so, but even if we couldn’t quantify it riders have known how important aerodynamics is to cycling. If you don’t believe it, think back to when you went really hard in a race, after a kom, or just tried to get through a stiff headwind section, you flattened your back, maybe got in the drops, and tried to get as small as possible. Even the great Eddy Merckx knew that getting down in an aero position would be an advantage, even if they didn’t know what to call it or why it worked.
Body position plays the biggest role in aerodynamics of a bike rider. Bigger than the aero frame, the wheels, skinsuits, etc, the body position is massive. Here we are going to look at how to position yourself and when to minimize your aerodynamic drag.
Aerodynamics and Speed
The speed in which you are riding, or more accurately the windspeed (the net speed of riding speed plus wind speed) is going to determine how big of an impact aerodynamics has at any given time. If you are riding into a 10mph headwind, it will make it significantly more important, but if you have a 10mph tailwind it is a good opportunity to sit up, get a drink, some food, etc, because the aerodynamic effect is lessened in the tailwind. We talk more about this in our other blog post about why aerodynamics matters at slow speeds. For this post we will look at how big of an impact position has and when each kind of position might be a good idea.
Riding with your hands in the hoods is often times the baseline of what we think when riding a road, gravel, or cross bike. It is the most comfortable to many, gives you easy access to braking, shifting, and great control on the bike. The issue here is that it is a fairly large aerodynamic penalty compared to other positions on the bike. We will use this as our aerodynamic baseline for comparison. Since it is the slowest position, its best to spend as little time here as possible.
If you need some relief from a less comfortable position, are eating, etc and this is the ideal position to do it, try timing it with a tailwind section of the course or when you are in a big group that is breaking the wind for you. This will drastically reduce the effective windspeed that you are experiencing and minimize any aerodynamic penalty you are facing. If you are in a group this or the next position on the list is probably your go to since you have easy access to the brakes and shifting.
This is the classic position when you think of getting aerodynamic on a bike. Hands down in the drops, trying to get a flat back, and still have all the control of your brakes and shifting. This is a great way to save some energy while still staying pretty comfortable. Compared to our drops position at 40kph/24.8mph we saw a 19.6w advantage! That is massive. If you were solo over 10 miles that is a savings of 35 seconds. It is more of a savings than being in the hoods and is best used as a position to be held for long periods of time, or to conserve a bit of energy within the group. If you are going for that solo flyer, keep reading down the list and you will certainly find some better positions to aim for.
This is what I would call the sweet spot for most solo efforts. If you are in road racing, it is still a UCI legal position, you are in control of steering, and can hold it for extended periods of time. Your hands on the hoods, but forearms horizontal, back flat, trying to minimize your frontal area as much as possible. Since your hands are still on the hoods you get most of the control of the bike but with the frontal area being reduced, we saw a 46w gain over the hoods position. That equates to a minute and 9 seconds savings over the hoods position for the 10 mile solo move.
The aero hoods position is not something you would want to do in a group since you lack the ability to hit the brakes, but if you are on the front or solo, this is absolutely a good way to save some energy or go a little faster. There is another position that is a little faster, but you will give up a lot of control and if you happen to be in a UCI race, it will trigger a few hundred Swiss Franc fine.
Puppy Paws/T-Rex Arms
Resting your forearms on the hoods has been really popular the last few years for the breakaway artists on the road. It is so fast that the UCI decided to come in and ban the position for safety reasons. When we tested this position we saw a 51w savings over the hoods position at 40kph. In that same 10 mile solo move you should see something like another 7 seconds over the aero hoods or 1:16 over the hoods position.
While this is a substantial savings, I would argue that the control and difficulty of staying in the position compared to the aero hoods position, it isn’t worth riding there. Unless you train in that position all the time it will likely make you sit up quicker and ultimately be slower. If you have some smooth tarmac and open road ahead of you, maybe this is the time to use this position. If the puppy paws position gets a little controversial, our next position will make half the riders roll their eyes into the back of their head.
There is a reason that time trialists and triathletes use aerobars, they are hands down the fastest position on a bike. We tested the Factor Ostro Gravel that has a bolt on aerobar option. When we rode in the bars it saved just shy of 62w at 40kph! That is absolutely massive. If the event you are doing allows the use of aero bars it can be an enormous savings. When we use the same 10 mile solo effort at 40kph that saves a minute and 28 seconds, 1:28!
We talk about this in our blog post about aerodynamics at slow speed, but if you are going slower into a headwind the aerodynamics are even more important. If you are doing 180w into an 18mph headwind we are all familiar with how hard and slow that ride is going to be. For a 180lbs rider you would be doing about 11-12mph in the hoods. Because you are going 12mph and the wind is 18mph all of the aerodynamics are acting like 30mph. That brings the aerobar savings to 120w or 14:11. That is 14 minutes and 11 seconds faster when you face that headwind.
We think all of these tests are really interesting, but how do you implement it for your own race? For most of us age group recreational athletes, we aren’t competing for an overall win at a big race, but we are trying to complete it and maybe even beat a previous time. Focusing on optimizing your set up for when it matters most is key. The last example with aerobars into a headwind is the most dramatic because you are actually moving fairly slowly but get a massive benefit. Anytime you have a huge headwind like this, it is essential to get yourself into a more aerodynamic position weather that be aero hoods, drops, or aerobars if you have them. This will give you the biggest gains for the given sector.
When you turn around and have that big tailwind, go ahead and sit up to rest your back, drink plenty, eat, and make sure you are following the most efficient line on the road. Aerodynamics is relative to the cube of speed, but rolling resistance is constant. If you are going 20mph with an 18mph tailwind, rolling resistance quickly becomes a much larger percentage of what is slowing you down.
By focusing on the biggest factors at any given time you can save a larger amount of time on course than if you look at just the average speed and the savings at that speed. Take a look below at our graph of body position and all of the savings at different speeds on our Factor Ostro Gravel bike. Let us know how you are planning to use this testing to optimize your position for your next big event.
Great info. I ended up raising my bars ( yes, raising!) so I could get my forearms horizontal while in the drops as this is where I spend almost all of my time.
@Paul that is certainly a good point. You could go a little more aggressive in his position, but Dylan and myself are both about 5’9" or 5’10" and I have always found it difficult to get my elbows parallel to the ground in the drops because I have to fold up so much that my knees would hit my arms. It is a bit easier for taller riders to get in that position but the key difference between drops and aero hoods is the amount of your forearm that is being exposed to the wind and getting your whole torso a little lower.
Why is there no comparison of a more aggressive position in the drops? This jumps from extended arms in the drops right to bent arms on the hoods (aero hoods). Couldn’t you be in practically the same position and still have better steering, braking, and shifting capabilities in the drops? I supposed it depends specifically how your bike is fitted.
Very Good info. Its nice to see the effects of the differant riding postitions, im all ways looking to learn new techniques to gain a little extra speed on my bike.
@Sam, yes the first number is the total w required to ride that speed. It does take into account rolling resistance losses, drivetrain loss, and aero loss. The changes are improvements over that baseline.
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