Pack Dynamics 4 - Phase 3 [January 2023]

Hey racing community!

We are back for another round of tests for Pack Dynamics 4.
I would like to outline in broad terms what has changed since the last version and what to expect coming into the next round of test events.

  • The concept remains the same - reducing the free forward motion inside the packs in order to reduce excessive speeds. Moving up in the pack should feel different (harder?).
  • With this version there was a change in logic in terms of how auto-braking works. It’s now more focused in the transition from medium to low draft whenever the Zwifter reduces power and is overtaking someone. This doesn’t mean it will happen only in the front (or near the front) of a pack, but mostly.
  • The previous system (auto-braking in high draft situations) is also still at work, but much less aggressive and mostly used for certain scenarios like when someone sprints at the back of a pack and then stops pedalling but still overtakes the whole pack or close to that (just a possible example).
  • A new change that was also introduced is that super-tuck is disabled when drafting. Super-tuck will still work if you have clean air in front of you. This came after the suggestion in the previous forum discussion, which is a possible way to reduce the super acceleration of packs in downhills. Please spread the word out that this is a feature and not a bug whenever you see it happening. This is also easily revertible in case we want to.
  • Double draft will be the default configuration.

For now, I won’t go into details about current configurations of how the braking is applied because we want to see how the first events go like a “placebo” test.
After that we can discuss it and see what needs changing.

There are already a few events setup for next week that you can see here: The at Home Cycling & Running Virtual Training App

Ride On!


Great, the above 2 should make racing a lot more interesting even without the other PD changes. Hopefully there will be a race on a circuit with a long enough descent to test the no-supertuck.

Did this get fixed?

I did found the issue, there is indeed some braking going on when your power drops below 10w, coming from some old code :man_facepalming:
The good news: it won’t be a problem after the next release.

Great news on on supertuck in the peloton

1 Like

Yes it was


James of Zwift Headquarters rolled out the new and improved pack dynamics today.

Features I noticed:

  1. Pack acts at more normal speeds, without the accelerated blob effect.
  2. Motion in the pack (moving forward or sliding backwards) was natural looking.
  3. The draft felt stronger, especially on the flat sections.
  4. Draft effect minimal on uphill segments, as you would expect.
  5. It was possible with a pack of 40 to regain the pack when you fall back off the lead group.

(Yes, I know this was a revision from October 2022 pack dynamics)

What were your thoughts?

1 Like

what could I say other than “perfect” ? You nailed it with this new pack dynamic !
Very nice and natural feeling, be it riding steadily in the pack (and it does it job perfectly, with an easy to ride pack), breaking away, moving in the pack etc. Descending in front i supertucked, and went out of supertuck as soon as i became second. Perfect.
It feels like IRL. LOVE IT


Sounds promising, but looking at ZP for this event and your wkg stats… how did you find yourself not just riding away from the rest of the field?

Thanks for coming!

I did, many times, then waited. I wanted to test many scenarii …


I suspect that light riders may get unceremoniously dumped out of descending packs even more so than currently. They will surely get dropped off the back of a heavier rider if there’s just two of them.

I don’t think so, as there is double draft, and the braking is much much lighter…
I tried on purpose to position myself behind and it was easy to stay, also the pack didn’t accelerate downhill that much : I breaked away on the uphill, and going solo downhill, the pack didn’t gain much time on me. I wasn’t doing big watts, so clearly the auto acceleration of the pack seemed not to occur.

I cannot do any of the races this week, but we’ll see!

Granted it was a group ride, but this did not happen today

1 Like

Unfortunately that’s what happens in RGT most of the time unless there’s lots of corners, due to rider height not being factored in to CDa. So far people who did the group ride seem to say its not the case, but we’ll probably have to wait for Wednesday’s race (although I don’t recall Sand & Sequoias having long descents so the jury may still end up being out). It might also be interesting to see the combined effects when (or if) downhill braking is finally implemented.

Sounds promising. Any vids?

1 Like

I think @James_Zwift has a youtube channel so there may be one there.

No, I generally wouldn’t record a social ride.

Noone needs to see me sending inane messages for an hour.