The Art of the Sweep

Zwift group rides are a great way to add a social aspect to your time spent riding indoors. Just like picking a pace partner, there is usually a group ride just about to start that caters for your target w/kg. Whether you’re looking for a recovery ride or want to push yourself, having a supportive and chatty group around you can really add to the enjoyment.

Once you’re in the group ride, we all know that the best place to be is snug in the draft, helping a big blob go as fast as possible. But today, let’s look at the Red Beacon and that special breed of masochistic Zwifter that seems to prefer hanging off the back, well out of the draft.

Who needs a sweep? (Well you are gonna get it!)

First off, why do some group rides even have a Red Beacon? I sweep for ZZRC, where our mantra is: we pace, not race. We start each group ride with the intention of getting every rider to the end of the route or time limit in one big, fast blob. Pedaling is easier in the draft and we want the best possible experience for everyone joining. However, sometimes things can go a little awry. From Zwift or Internet dropouts, to answering a phone call, or a brief lapse in concentration, it’s pretty easy to suddenly find yourself out of the draft. Once you’re off the back you need to output more power than the target w/kg for the ride to get back, and that’s where you might need a little help.

The Integral Principles of the Structural Dynamics of Flow (aka Drafting)

Before we look at sweeping, it’s good to examine the dynamics of the draft. Have a look at the picture below taken in “draft viewing mode” (the developer-only mode with rainbow streaks):

The best draft is directly behind the rider in front, and it dissipates as you go wider. The size and strength of the draft also increases the more riders you have. If there are just two riders, the Zwifter behind can get away with outputting around 25% less power than the first rider. If you have a bigger group, that saving can increase to about 35%. It’s using this math that we can get a dropped rider back to the blob without them going too much over the target power.

To sweep, or not to sweep, that is the question

The simplest sweep starts when someone has a drop out. As Red Beacon you’re looking for when someone’s watts go to 0 or, better yet, there is a message asking for help. The sweep team will then ease and drop off the back of the pack, often with a message to say they are coming to help. This is also a message to the leader that a rider needs help – if they’re a long way back the group may need to slow a little – and a signal to other strong riders that they can come back and support Red. Once we’re back with the dropped rider, we spin up, get in front of them, and start pulling them back at around 25-40% more than the ride’s target power.

Things aren’t always that simple, though. Often the rider will not have the Companion app. Sometimes a rider has gone back to do intervals and you get there and they shoot off doing 6 w/kg. They may also be winding down, or are simply happier bobbing along by themselves at a slower pace. It can be lonely trek back if you go to help someone that doesn’t want/need it, so you have to make smart decisions on when to drop. I generally look for riders still holding the ride target w/kg. If they can do that, and we have a big enough group, even a minute gap to the Yellow Beacon is chaseable.

With Great Power Comes Great Responsibility

A well-executed sweep is a team game that requires some skill and coordination, not just pumping out the big watts. We recently rode The Magnificent 8 with a target w/kg of 2-2.5. As Red Beacon you always hang back a bit at the start to pick up the stragglers that are slow leaving the pens. Everyone is fresh so should be able to hold the advertised power comfortably at this point. You blob up with the other riders and lead everyone back to the group, making sure to let them know when you’re going to up the pace to close on Yellow.

As a sweep, any incline is your friend. As long as the main group are keeping to the advertised pace you can use them to close any gaps more easily than you can on the flat. 2.5 vs 2.0 w/kg will close a gap faster at 3% than 0%. The steeper the gradient, and the more you go above target pace, the quicker you catch the group.

Equally, descents are evil. I try not to waste watts chasing on a downslope. With a big group, the effect of the draft is too strong and, no matter what you put out chasing, all you’re doing is limiting your losses. That means as you reach any summit you encourage riders to push up and get in the draft behind Yellow.

That can be asking a lot of a rider that has just been pushing as hard as they can up the climb, so riders off the back are inevitable. On The Magnificent 8 that happens after Hilly KQOM Reverse. Big splits can happen on the fast descent and you have a long, hard, flat slog through the desert to get back to the group. A fellow sweep and I picked up a couple of riders and started heading back. We would see other riders up ahead and type: “jump on as we pass” in the text box. It’s important here to slow down as you go through. If you keep up the sweep pace you will shoot past, so ease off before you get to them and give them a chance to latch onto your draft.

Does my bum look big in these bib shorts?

At this point, I am jumping to the camera of the riders we’re sweeping. I do this for a few reasons, and not just to check out my own rear end. First, I want to be staying about 1-2m ahead of them and doing about 25% more power. I monitor the gap. If I pull ahead too much I need to ease off the pace. If they close I can quickly spin up. I find it easier to gauge that from their camera angle, not mine. I also want to see their heart rate. Are they pushing themselves to an extreme already? Do I think they can do more? Should we ease off a little? Can this rider make it back? Having their information on my screen gives me some insight into this, especially if they are not chatty.

By now we’ll have all the sweep team around us, about five strong riders, which makes the job easier. We have a rider whose heart rate is 171 but they are not letting up. They want to keep going and that makes me even more determined to get them back. A quick message to check they are ok and to instruct them not to do more than 2.5 w/kg. Even if we don’t get them back, I want them to finish the ride and to have enjoyed it, not felt like it was an hour of misery.

Sweeping Is Basically Team Time Trial Practice

This is where our draft dynamics come into play. We need to line up in a formation where the riders at the back of our blob are holding what they feel manageable: 2.5 w/kg in this example. The riders directly in front of them need to ride around 3.0-3.2 w/kg, but absolutely no more. Any more and we drop our precious cargo. We then have another wave of riders that can all hold 3.9-4.1 w/kg. Then it’s a fine balancing act. Am I still in the draft of the rider in front? Is the rider behind still in my draft? Is my power output stable? As long as we’re all cognizant of what’s happening around us, and we have some sweeps pushing over the advertised pace, we can get any rider back to the blob.

Our story has a happy ending. This was a Level 6 rider doing their first ZZRC group ride. Our Yellow Beacon gave words of encouragement and other ZZRC riders soon followed suit. The chat filled with people urging us on. Ride Ons rained down in a giant Thumberstorm and the chaser got their “You’re Famous” badge. We managed to reattach towards the end of the underwater tunnel and everyone could enjoy some respite in the loving embrace of the blob.

Was it incredibly hard for that rider? I have no doubt. Did that rider return for another ZZRC ride? They joined one the very next day.

And so, my fellow Zwift group riders: ask not what your sweep can do for you – ask what you can do for your sweep

Everyone involved in leading or sweeping group rides invests a lot of their own time and effort. At ZZRC we want it to be as enjoyable and inclusive a Club as possible. We do it because we love it, and I have no doubt it’s made us all better cyclists. I am twice I was when I first randomly stumbled into a ZZRC Saturday Social Club feeling very hungover. That said, we sweeps do have a few requests:

1. An early shout for help if you’re out of the draft saves us both a lot of effort
2. If you’re deliberately off the back because you want a harder ride, or you want to do intervals, or want to help sweep, that’s great! Just let us know in the chat
3. Also let us know what power you’re comfortable holding. Again, we want this to be enjoyable for you and there are times when the best thing we can do is just pace with you. We also enjoy doing just that
4. If you’re feeling strong and can hold above the advertised pace, please volunteer to help. We really appreciate that and the more support we have the better
5. If we drop back and it turns out you can hold over 4 w/kg, we reserve the right to get towed back by you!

See you all out there!