Unless you plan to always ride by yourself, drafting is an essential skill for the cyclist–both indoors and out.
The goal of drafting in Zwift is to conserve energy, just as it is outdoors. Estimates vary, but the number most often thrown around outdoors is a 30% power savings when drafting behind just one other rider. In terms of real numbers, this means you could put out 210 watts while drafting and maintain the same speed as a solo rider putting out 300 watts. Riding in a large pack will reduce wind resistance even more, resulting in greater power savings.
Drafting Power Savings in Zwift
Based on our (admittedly limited) tests, drafting in Zwift gets you a power savings of approximately 25%. Using power emulators on a closed course, we had one rider sustain 300 watts while another ride drafted behind. We found a rider could stay in this 300 watt draft at 225 watts while on relatively flat ground.
Changes in pitch effect these numbers, as gravity comes increasingly into play. Using the above power numbers, the front rider will pull away on an incline. But when a decline hits, it will take even fewer watts to stay in the draft.
While we didn’t find any additional power savings when drafting behind two riders instead of just one, our tests were not completely thorough in this area. Based on our experience, we suspect a greater draft effect in larger groups.
The Challenges of Zwift Drafting
Zwift HQ has done a commendable job of tweaking their drafting algorithms to arrive at what we have now, which works quite well. That said, drafting in Zwift takes some getting used to, even if you are familiar with drafting in real life. Here are the differences:
- No brakes: when you ride outside, you can tap your brakes to maintain the proper distance off the back tire of the rider in front of you. There are no brakes in Zwift, so your position becomes a matter of putting down the right amount of power at the right time, plus a little bit of luck.
- No steering: outside you can steer in and out of a draft. There is no steering on Zwift, which means at times the game places you behind someone you are trying to avoid, or doesn’t place you behind someone you’re attempting to draft behind. Again, this comes down to power placement and a bit of luck.
- Limited and delayed sensory feedback: outside you can feel when you’re in the draft: the air resistance decreases and you don’t have to work as hard to keep the pace. On Zwift, there are very limited cues as to when you are in the draft or not. Additionally, if you need to modify your power output to stay in the draft, the response (your avatar moving in response to your power change) is not as immediate as it would be in real life.
Zwift uses the visual cue of sitting up as an indicator that you are in the draft. It can be a little confusing though, since Zwift will also have your avatar sit up at slow solo speeds.
If you are moving at 33kph or more and your avatar is sitting up (on the hoods), you are in the draft.
In our tests we’ve found that, when riding solo, you will begin on the hoods. As you speed up, when you hit 32-33kph your avatar will move to the drops. If you are in the drops and begin to slow down, your avatar will move to the hoods as you hit 29-30kph.
Since Zwift steers for you automatically, you may at times find yourself being steered out of the draft. If this happens while you’re attempting to stay in the draft, simply keep your power at a level that keeps you in a good position to get the draft, and Zwift will typically steer you into the draft soon enough.