Pack Dynamics 4 - Phase 3 [January 2023]

From yesterday’s Virtuslo GC B race on London 8 (PD4 event). I captured my descent of fox/box (I don’t know which) with three others. I got dropped when I wasn’t contributing and the others were attacking or at least lightly working. Definitely was briefly confused/lulled by the temporarily-broken supertuck indicator, but otherwise I think it probably behaved quite well. I knew about that breakage but I was gassed and not running on 100% brainpower. Overall, I’d call it a win for PD4 because if I had been paying attention I think it would have been relatively easy to stay on.

Twitch (2m20s)

Sorry, my webcam was acting up so my video is choppy but please don’t look at me anyways. The Zwift feed itself is solid.

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As I mentioned earlier, we are setting up a six week race series with PD4 enabled. If you are interested to test PD4 in a ‘real’ race environment, please join us.

I will feature points races, TTT, and another format that has elements of both. The whole series is team based, but if you cannot file a full roster, we can hook you up with another team.

In short:

  • Team based (min 4 racers, max 6 per race)
  • Auto-categorization of whole teams, mixed ZP cats allowed, PD4 enabled
  • iTT, Points race, TTT, Team Points Hunt
  • Saturdays, 6 weeks, starting on 25th February

Team registration

@DejanPresen I would love to see a VirtuSlo team in the series! Check it out if you are interested :slight_smile:


@DavidP i don’t know how this guy is testing this but it would be amazing addition to PD4…corner breaking looks good.

That is the corner auto-braking feature and it has nothing to do with Pack Dynamics 4 (contrary to what I’ve already seen somewhere online :man_facepalming: ). The way to distinguish is that you also see red number in the speed value and bike rear light flashing.
PD4 only flashes the power numbers.

Just be a bit more patient, I think some work still needs to be done to perfect the system on several different types of courses.


Any further changes planned for PDv4…i can see already lots of organizers using it.

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Current plan is to rollout to more events and activate it globally in one of the pace partner worlds soon.
Given that I haven’t seen no negative feedback lately I’m not planning on changing configurations for now. I’m always open for constructive feedback.


I’m all for progress and adjusting the realism of the racing experience so I support some level of trial and error on an opt-in solution. In a PD4 race today, a few of the larger (heavy, tall, large watts) riders were having issues holding wheels. I was the most vocal about the situation and have the most Zwift Racing Experience of the concerned racers.

If I was on the front of a small group 3~5, I could control the speed easily which was great; however, on a few occasions I would be overtaken and then in the blink of an eye my Power would flash red, and I was dropped which except for the power flashing red, I’m all for losing the front spot if those behind me want to push the pace. There is where my happiness ends.

If I worked hard to get back in touch with the group and then eased off the power to rejoin instead of overtake my Power would again go red and I was shot out the back once again.

I’m not sure exactly what you are doing when the power goes red, but might I suggest capping the speed instead of having a virtual power drop or removal of all draft or whatever is happening, as it currently feels too extreme? When I’m in an IRL Group Ride or Race I do the same, when I lose touch with the group in front I push to close the gap then give a few soft pedal strokes to calmly regain position instead of overshooting the next wheel in the paceline.

It felt today almost as if w/kg was more important on flats than pure power as I’m accustomed to. I’ll chalk this one up to doing VO2 work recently, but the same people who could suddenly drop me on the flat putting out fewer watts I could pass at will on a 5~7% gradient at similar w/kg which also felt strange but may be unrelated to PD4.

Did your power blink red when you were in the draft?

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David, is it still Zwift’s ultimate aim to enable PD4 as the new default for all activities on Zwift (rather than some form of opt-in)?

To me it feels like you had Power dropouts…while your power numbers flash Red you are autobraked to the speed of the group and not shot out the back. What you experienced was more related to dropout…did you check Zwiftalizer if you are using ANT+

No drop outs, my hr sensor (v1 wahoo tickr x) isn’t happy but my neo2T is. Zwiftalizer 2.0

Yes I saw it flash red as stated above. Of course the one week I didn’t stream this race due to child distractions.

I hope this is rolled out to Pace partners on familiar routes for testing before it is adopted.

At the moment this topic is under racing and I know there are people who never do any races in Zwift, so they will miss being able to check this out.


Yes, the final plan is to turn it on 100% for everything. Events and free riding.


A friend of mine raced the KISS 100 on Triple Flat this morning and was less than pleased with how it felt in the back half of the pack. As long as you’re in the front half to third it was fine but as soon as you were towards the rear, it felt like there was no draft. He’s big guy, 92kg/193cm and is a solid B rider. Lotsa power on the flats so this would be notable for him to say. I’ve not ridden PD4 myself but I’m looking forward to seeing if this plays out correctly.

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Did he get red numbers?

Couple of things that could be happening:

A. As it creates a more realistic drafting experience, riders that have become accustomed to surfing the back of the pack (me included) may find they now need to proactively position themselves further up or find life tough. I’m not 100% why this is the case with pd4, but it is more like irl. @DavidP do you know why with pd4 it feels tougher at the back of a pack?

B: you can lose draft by being pushed sideways by a rider coming through, and at the same time receive some autobraking. The combination of some autobraking and loss of draft may feel like a bigger hit to heavy riders who have to put out more power to maintain speed of the pack (hypothesis only)

C: neither of these things are actually happening and it’s something else / just needs more practice.

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I think that could be because the people that in pd3 were used to riding without trying to maintain the position were going to the front and then to the back without losing much speed now when they go to the front they lose more speed and so they have to push more to regain that speed when they are in the back

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[quote=“Wesley Stocker L13R [DIRT], post:142, topic:600725, username:Wesley_Stocker_DIRT”]
I’m all for progress and adjusting the realism of the racing experience so I support some level of trial and error on an opt-in solution. In a PD4 race today, a few of the larger (heavy, tall, large watts) riders were having issues holding wheels. I was the most vocal about the situation and have the most Zwift Racing Experience of the concerned racers.

I got the same impression as you had from the test races I attended, with regard to staying at the back. I wasn’t sure if it was caused by some breakaway attempts or my having a cold/asthma, so I didn’t want to mention it.

It felt much harder to stay in the same position at the back than what I’m used to with PD3. I couldn’t allow any gaps to the riders in front. With a field of 30+ riders, it should feel easier at the back than closer to the front, but this was not what it felt like. I had to move into the more dense part of the group where it felt easier. Not much red blinking anywhere. The draft at the back should be much better with DD at the back than what we are used to with the normal draft. I don’t think it felt like staying at the back of a bigger field IRL.
Also, it seems like it is almost impossible to stay right behind a rider. I’m always placed to the right or left, taking more wind than nessesary. IRL, I would have tried to glue to the wheel in front. This is probably nothing new with PD4, I just noticed it more when in the test race.


From my experience and from reading above i think what is happening at the back is what David mentioned in the 1st POST

Riders at the back don’t have less draft but because they are not moving free to the front they are puting more watts and it feels harder. There is no visual acceleration and this is now different than PD3. With a group of riders infront, you can’t just jump to the front.

Here is my stream from the current PD4 version. You can see all the data from Watts, Wkg, Draft %, bpm…i’m at the back off the pack and i have to push hard because the pack is accelerating past me but i don’t have any real problem to get back…you can see me drop Watts and get Red numbers to stop my free forward motion.


Yes I know exactly why, and I’ve explain it before. It’s a case of visual perception that is different from what you are used to. Because now you don’t “surf” to the front so easily, those who are towards the back of the pack tend to keep pushing more to move up creating some sort of fight at the back :thinking:
Like you said, perhaps it just needs more practice to get used to the new system.


We have also been seeing a phenomenon in the Pack Dynamics 4 events, which is riders pushing more than usual on average (perhaps to test the system? try breakaways?). I personally did a group ride the last week that felt much harder than the advertised pace because people seemed to be pushing like they were in a race :man_shrugging:

Another thing I observed while analysing lot’s of races (not only PD4), is that a lot of riders attempt breakaways with very mild accelerations just causing the pack to string out. To establish a proper breakaway you need to see orange numbers on the right hand side bar :wink:
(this is a general observation, nothing to do with your comment in particular)