Come test out Pack Dynamics 4.0 [October 24 2022]

If this works, it will be a true game changer for racing! Fingers crossed😅

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Sounds amazing, please please, please make this more realistic as it kills racing! You can’t have a pack of 15 riders catching a person who is doing significantly more power than they are at the front of the pack. It just encourages sandbagging as you know you will catch the rider doing the breakaway at a very much lower wkg/effort output. It needs to be a major reduction in pack effect to make this work

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well i am very glad that the physics are being looked at but the mechanic in me is telling me that it would probably be better to make one adjustment at a time and test that before slapping double draft and stuff on top of it


I really like this idea. Hopefully it quashes the sandbagging a bit more by allowing breaks to be more successful. Less sitting in and sprinting for those upper B and C riders.

Now, one thing that would be nice to see is trainer resistance decrease in the draft. Probably a back burner thing.

Resistance increases and decreases based on gradient. Interested to hear why you think this should decrease in the pack?

Who is this fancy JM pack dynamics wizard?

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It seems like right now the way the pack dynamics incorporate draft is by adding “draft watts” to produced watts. While it’s numerically the same end result in steady-state, the side-effect is the “churn” in that when a rider enters the draft they start accelerating.

I don’t think there’s a perfect solution though, because reducing resistance in the draft would only affect smart trainers. Those using dumb trainers with power meters or zPower would still have to use the current draft model, and the “churn” will still happen. It would be like the olden days when dumb trainers would still produce power downhill but us smart trainer users would essentially get 0 resistance.

On the other hand, it may just add to the “feel” of the smart trainers without much detriment. You could essentially “feel” when in the draft and when losing the draft, instead of having to watch the screen. Make it easier to throttle effort, even when the churn is going on.

If the dynamics being tested address the churn, then it may be a really good bridge.

Just my rambling thoughts.

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Because IRL there is wind, and air resistance, so when you are in someone’s draft there is literally less resistance to push against. I think anyone who has ridden outside and gotten into someone’s draft would notice that it takes less effort to pedal at the same speed.


But if you’re putting in X watts, and your wattage is increased when you get into a draft, then it would take less effort to pedal at the same speed. Because your input of X watts, plus the draft effect, now makes you go faster, so you can now ease off your own effort in order to do the speed you were doing before. Less effort for the same speed. If the drafting effect added watts and also eased trainer resistance, you’d be getting a double effect.

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This is one way that a game could work, and I believe I saw an interview with Jon Mayfield years ago where he considered it, but it required trainer support. I’m sure more trainers now support that, it’s the way that VirtuPro works. I think there are pros and cons to both methods.

Hope we can get one Test in Late Afternoon/Early evening in EU Zone. I just can’t make this one at 14:00CEST. Would really love to test it.

I just signed up to the event and i see you mentioned that the ride is on Wandering Flats…but in Companion it’s Countryside Tour

Next iteration of these events can we get a few at various time zones so we can get participation across all geographies? Would be great if it had a somewhat similar setup to times like ZRL with 3 or so core times (morning US / late APAC which will be harder with time change | EMEA | evening US)

Just to get additional participation. The current one is at a bit of a weird time that I don’t think is peak usage time.

I don’t know where you get the idea that your wattage is increased in the draft. I suppose it’s possible that someone could design such an approach but it’s not the natural way to model the physics. Zwift is a cycling simulator and the physics of cycling is well understood.

How does Zwift make you go faster in a draft with less effort? Is it by reducing the trainer resistance, or by increasing your speed at the same input wattage?

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Yes, that option.

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Not that Wandering Flats has many corners, but will this be combined with the previously promised corner braking ? If so then this could make Zwift racing much more realistic in time for the next UCI indoor championships.

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Yep. I just already had this time slot available. I suspect I’ll get a couple hundred turning up though.


No, not yet. This is just pack dynamics.


What’s the projected timeframe to launch final version of this… ie. test, learn, refine, repeat, launch?

Also, I presume this would be applied to all riding, not just races. Ie. pace partner rides etc?

92 signed up at the mo’.

Any idea how you expect (or want) this ride to pan-out? Is it going to be a free-for-all from the gun or would a more disciplined approach be better? Somehow doubt it will adhere to the D-cat pace :wink:?