21 February, 2017

A Comprehensive Guide to Drafting

The science behind drafting in road cycling and the strategies of how to take advantage of the so-called slipstream

Disclosure: This article may link to affiliate sites/feature complimentary products for review purposes.
astana team time trial
Photo by Ruaraidh Gillies

The first time I ever rode with a group, it made me nervous to see how close all the other riders were to each other. Mere inches separated some front and back wheels between two individuals. Yet on this relaxed afternoon ride, it didn’t seem to phase anyone but me. I was still new to the bike, and very out of shape compared to my future teammates who had just finished off their race season. Needless to say, I was suffering pretty hard. “Get on his wheel,” one of the guys told me, referring to another guy in front of me. I moved so that I was in line behind him. “Closer,” I was nervous, but everyone else was nearly touching wheels, so I decided to have some trust. And suddenly I wasn’t suffering so much anymore. “Do you feel the difference? That’s called drafting.”

Drafting (also known as slipstreaming) – it’s a basic skill that every cyclist should know. But in terms of other sports, drafting is pretty unique to cycling (and maybe NASCAR racing), so if you’re new, its something you have to learn. And, trust me – you’ll be happy that you did.

The (Basic) Science

The science on how drafting works is simple, at least to understand. Trust me when I say the math behind aerodynamics is not so simple, but we won’t touch that absolute nightmare.

Basically, a lone cyclist moving through space disrupts the air, which moves around the individual’s bike and body, creating a a space of turbulent air behind herself. This turbulent air has lower pressure, and thus a lower resistance than the air in front of the rider. Think the difference between riding in a headwind and no headwind. The former has much higher air resistance than the latter, and thus is more difficult to move through. So if another cyclist moves into that space of turbulent air behind the first, they are essentially doing less work to maintain the same speed as the first rider. Depending on how close on her wheel (the closer the better), up to around 30% less work. A third or fourth rider will get slightly more benefit, up to around 35% less work, but after the fifth rider in a line, the benefit levels off.

More Science!

Hey, I’m studying to be an engineer, can you blame me for being excited? What most people, and even many cyclists, don’t know is that grinding it out at the front does not just benefit the cyclists on your wheel – there is also a slight benefit to you! Admittedly, it is nowhere near as high as 30% less work. But some studies show that with someone filling up the turbulent air space behind you, you will benefit with 3-5% less work than grinding on your own. And this effect also affects the individual in the back of a line – which is why it can feel just slightly more difficult to be at the caboose than in the middle of a group.

This is all on a flat road, at high speeds, with riders of all the same size, and with no prevailing winds. The science gets a bit more tricky when you add in those factors. For instance, drafting becomes less advantageous while climbing – this is normally due to the lower speeds, where there is less air resistance to begin with, and thus the turbulent wake behind the first rider doesn’t form as drastic of a difference. Also, if you are a small rider, drafting behind a larger rider will give you a much greater benefit than it would if you were the same size. Think standing behind a brick wall to escape wind as opposed to a telephone pole.

astana team time trial
Photo by Ruaraidh Gillies

The Paceline

We’ve talked about what drafting is, but how do you use it while riding? We’ve all seen a peloton, a large group of riders spread out across the road. Drafting is used here, sheltering the individuaEEls in the middle and back of the group. But when you’re not riding on closed road where you can take up that much space, or you don’t have 30-100+ riders in a group, or when you’re in a breakaway with a small group in a race, chances are you’ll end up in something like a paceline.

In a paceline, the rider in front takes a “pull” – one to a few minutes of hard work. After their pull, the front rider will pull off to the side (obviously checking for cars or other obstacles as necessary), allowing the line to pull through past them until they can slide back in at the back of the line. As a side note, this last bit is easier said than done. You will need to accelerate back up to the speed of the group just in time to slide over, or you risk getting dropped and wasting more energy trying to grind back into the slipstream. It’s not difficult, per se, but takes practice to get the timing right.

The Rotating Paceline

The image at right shows a particular paceline formation. The rotating paceline, sometimes called a circular paceline or the Belgian Tourniquet (how awesome is that name??), is a slightly more difficult version of the paceline. I’ve done it with my teammates a few times, for fun or because we are late getting back from a ride, usually. Instead of a single line of riders, there are two. One side is moving “forward” relative to the group, the other side moving “backward” (of course, you are all moving forward, just at different rates). At least four riders are needed for this strategy to work.

As soon as there is enough room for the first rider in the “forward” line to slide over in front of the first rider in the “backward” line, they do so. As soon as the last rider in the “backward” line falls behind the last rider in the “forward” line, they shift over. From a bird’s eye view, the riders seem to be rotating in an oval. What results is shorter pulls at the front, while still maintaining the shelter of the draft for those behind. This way the pulling rider can put in more work per unit time they are at the front. It requires much more focus and spatial awareness than the simple paceline, but dang is it fun.

Paceline Etiquette

First, and most importantly, be consistent and steady. A paceline only works when the individuals keep their wheels close together to get the benefit of the draft. But that can be incredibly difficult to do, near impossible, when the speed is constantly changing or when sketchy riding makes trusting a wheel difficult. So relax – keep your pedaling smooth, maintain a straight line, and maintain as consistent of a speed as possible. Otherwise, you or someone else in your group might “lay their bike down”, as they say.

Secondly, if you’re on the front, always keep pedaling – even on descents. When you’re in a paceline, everyone behind you is working a step down from what you are. If you’re pedaling hard at the front, they’re pedaling easier. If you’re pedaling easy, they’re coasting. And if you’re coasting, they’re either braking and wasting energy, or not braking and running into your back wheel. Again, the lesson here: don’t stop pedaling when you are on the front!

Lastly – take your pulls at the front. There’s no need to be a hero, especially if you’re struggling to stay on with a fast paceline. But don’t be a wuss and pull off as soon as your nose touches the wind, or avoid the front all together. Take twenty or thirty seconds to carry your weight, then pull off if you’re really suffering. But chances are, especially if you are in a breakaway paceline, if you’re hurting so is everyone else.

What About Crosswinds?

cycling echelon pro cyclist
Photo by smthcriminal29

Ahh, crosswinds. For a lightweight human like me riding a relatively aero-framed bike, it’s the bane of my existence. I’ve been in crosswinds where I am literally leaning over into the wind to keep it from pushing me off of, or in to, the road. But you know when crosswinds aren’t so bad? When you have a friend (or two, or several) to echelon with. A significant crosswind throws off the whole aerodynamics of drafting. Sitting in the space right behind someone isn’t going to help you when the wind is coming at your side rather than from the front. But when you stagger off to the side opposite of where the crosswind is coming for, there you will find your slipstream. This staggering is called an echelon.

Unfortunately, there are only so many riders that an echelon can hold, because the road is only so wide. Picture four riders in an echelon formation, with a fifth hanging on in the space behind the fourth rider. This poor sap is in what is known as the “gutter”. This is a bad place to be. In the gutter, there is little to no benefit from drafting, depending on the angle and strength of the crosswind. If you’re alone in the gutter – sucks. You’re going to have to suffer until you can worm back into the echelon and push someone else out. If there are more than one of you stuck behind the front echelon, however, you need to work together. Form your own echelon in order to avoid being spat out the back.

On Safety

A final, very important note: drafting, while awesome, can also be dangerous. New riders are nervous about drafting for a reason – there is less time to react to anything happening to or from the rider(s) in front of you. Those massive pileups you sometimes see at big races? Guess what – hanging close to each other’s wheels is why the vast majority of those riders in the back end up part of the pile. I once crashed because I was following very closely to a rider in front of me and didn’t have enough time to react to small, but sudden, movement. Only draft on riders you trust, stay alert, and be smart! And then, enjoy your 30% less work. Ahhhhh…..

About Ellie 6 Articles
Former varsity rower turned cyclist, Ellie is in her second and last year of collegiate racing before going on to explore new roads. She hopes there are nice views and cute dogs there. Currently, she primarily rides in the farmlands of Pennsylvania and along the beaches of California.

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