Pack Dynamics 4 Release [April 2023]

Hey folks,

This post is to let you all know that after months of testing, we’ve released Pack Dynamics to all of Zwift today.

As of the time of this post, Pack Dynamics 4 is enabled for all worlds in Zwift. This includes all activities and all events.

What is the benefit of Pack Dynamics 4? Simply put, the distinct aspects you should notice are as follows:

  • Larger packs should have less rider movement than before, with riders holding more consistent positions; your avatar will shuffle around less in the groups.
  • Provided the group is riding consistently - as they might do with Pacers - and the pace is not changing drastically, Zwifters that are dropped from a group should now have an easier time bridging back up to the group.
  • Zwifters that attempt to breakaway from a group should now have a slightly easier time staying away. This does not guarantee more breakaways, though. You’ll still need to work together to keep the peloton behind you!

Overall, we are looking to make riding in a larger group feel more realistic while still maintaining the distinct feel of Zwifting.

Enjoy the new changes!

Ride On :ride_on:


Is the flashing red watt number indicating that you’re being braked in effect in all ride types, and in all circumstances where your avatar is being artificially slowed?

It will flash red at all times now when you’re being slowed, instead of just in events.


Really excited to go try it out now that it’s everywhere. I am personally happy the red UX is showing up, but if there’s no first run experience for it my guess is we’re going to see a bunch of confusion in the short term when people who haven’t been following these threads see red. Guess we’ll see :slight_smile:

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It would be more helpful if it flashed the wattage you’re being penalized.

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The issue with the red for me is you only get it after you’re slowed, and it’s so short you can’t do much about it at that point. If there was some way to say ‘you’re gonna be slowed if you keep this up in a few seconds’ then I’d be able to react and save a bit of energy then and there. I guess after living with it for a bit we will learn how to best avoid it even showing up and get better at proactively slowing down as we approach the front of a pack etc.


Great! I’ve done few races and couple of rides with RoboPacers in Makuri using PD4 and I enjoyed.


Brilliant, thanks to everyone at Zwift for their hard work (and patience) in delivering this, it’s much appreciated :+1: @DavidP


I haven’t been following these threads but I’m confused now, just reading this! Why is it going to slow us?

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In fact it’s not. The numbers turn red whenever the “virtual brake” on the bike is being pressed. So it’s during the slowdown process.
But I understand what you mean in the sense of wanting to anticipate the actual braking.


By “all times”, do you mean really all times you are slowed down, like when moving up inside the pack, or just when the braking is above a certain level?

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He means for all activities (not just races).

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I kind of got that. I wanted to check if there has been any changes to when we see red numbers.

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It’s to try and stop the ever-increasing speeds that you can get in a large pack, so that it’s not impossible to get back on if you’re dropped, and not impossible to make a breakaway.

It only is supposed to “slow” you if you’re easing off the power in a pack and even then only under certain conditions. So don’t worry about it - it’s not going to slow you when you’re actually trying.

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Perhaps had my first real test of PD4 in Tour of Watopia stage 5 tonight (short course Sand and Sequoias).

I finally saw some red numbers. Occasional infrequent flashes but the biggest auto-braking was when I rolled into the back of a pack doing 30W. I think that’s perhaps the intention though. I never felt I was being braked out the back of the group.

Still managed to finish with the second group averaging 3.4w/kg while the rest of the group was between 3.6w/kg and 4.4w/kg (a couple managed to ride off the front doing 4.5 and 5.1w/kg). I feel I can still sit on the back and take it easy although there were a few times I had to push back on to the tail.

There are certainly times where the pack will increase pace and stretch out and you can’t sit back and rely on the magic of the blob to bring it all back together but again, I think that’s the intention.

Old pack dynamics was a thing. PD4 is a different thing. Neither are like the real thing.


Zwift team: I think you’re unnecessarily complicating the topic for your users. There are 2 things that can slow the rider, natural physics/gravity and force applied through brakes. When you tell your users they are being braked of course they are going to react as if the game is unnaturally penalizing them. If you just differentiated the terms you’d solve your user problem without needing to change the actual technical mechanism that reduces rider speed.

No one would complain if you just told them physics is slowing you down, no power input into pedals means velocity decreases from air resistance. Just don’t say the brakes are on. The same way when a rider goes downhill and speeds up it’s not like you then say the virtual after boosters are on.


The auto-braking is a new feature and actually something rides can relate to from IRL riding in a pack. To say that the physics is slowing you down, would be kind of a lie. This is an external force applied to the riders to achieve certain behaviors. They could say: “We are pressing the brake for you in situations where we think that is your intention”.

Riders should be allowed to complain if it acts strangely. That is the only way to improve.


My first experience of it in Watopia is with Constance group doing 47.2km distance on Tick Tock with 44.6km/h average speed in a group of about 8-10 riders with a very powerful French rider doing most of the leading at 4.6w/kg+ (sometimes above 6w/kg).

From the racing topic, to answer the guy before, not just “noodling around”. :wink:

What I did notice sometimes if I managed to get to the back was that I had to blast 6w/kg or more to try and get ahead of the rider ahead doing 3.5-4.0w/kg otherwise I just seem to stay stuck behind them - not good if a gap is forming in front of them.

6-8 of us near the end did a push and managed to destroy Constance and a WMZAU rider - we ended up leaving them 13 seconds behind with our push. It wasn’t super aggressive acceleration, just well coordinated.

I’m less than 60kg and average power for the entire ride was 210w. I also rode the same route yesterday with Constance and exact same average speed, this seemed harder at times than PD3 yesterday, but if everyone kept steady pace, it was quite okay.

Monday and Tuesday both riding with Constance on Tick Tock route and PD3, today PD4.

This is worthwhile, but the average speed today versus yesterday in our “A” bunch was identical (44.6km/h average with about 10 riders) and my average watts were only 1 watt different. We could make a breakaway today if we pushed the pace up (which we did) and left heavyweight Constance and the following rider way behind.

I didn’t notice any flashing numbers at all on MacOS Zwift - so maybe in robopacer rides we aren’t allowed to see that.


In the previous thread it was stated that the red flash was only going off during “the most aggressive braking situations,” to clarify is it now flashing red any time the autobrake is being applied to any degree?

If this is true, then I would expect the most natural place for auto-brake to be applied would be when riders take a downhill hairpin at 75kph but i suspect that isnt going to happen