Pack Dynamics Test Events (December 2022)

In that particular race the 2nd place rider was already on his 3rd ride of the day (at 10:45am!) and l guess might have been more interested in racking up distance for the Rapha 500 challenge than producing a sprint finish in an insignificant race. But in general terms, young children can be impressively quick.

I would rather it be some modifier to drag savings but ultimately the effect is to reduce churn, right? I assume it won’t be pack or collision detection. Triggering the slowdown based on sudden reduction of draft benefit instead of reduction of power output is the way to look I think. I also think if you/we can crack the churn issue in a 0w descending group that the solution will be applicable to everything trying to be accomplished with no more than minor tweaks.

I was trying my best ha ha! I was beaten fair and square!

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Any way you look at it, it was an impressive performance. Though I frequently see references that raw power is pretty much what matters on flat courses, and w/kg (relative effort as term has also been used) isn’t as important. I’m not really seeing it in this example.

Interesting idea. Would give the light riders who can blast a climb an actual advantage instead of guaranteed drop on the descent. Just have to figure out how to apply it to a big group as the people on front won’t have draft.

Those people on the front can still aerotuck. Don’t mind that.

This is already a feature request BTW. I put it in separately because better to focus on the churn in this thread:

FR: Only allow supertuck if there is no draft

I think that alone would reduce descending churn. Front row tucks, everyone behind gets draft benefit but no tuck and would be a lot more stable.

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It does however mean that many more lighter/taller riders will just get dropped on every steep descent (draft benefit without supertuck often isn’t enough for them) and there will be nothing they can possibly do about it. I’m not sure it will meet with universal approval!


I was just about to write the same thing. Aero penalty from getting out of supertuck on >80-90 km/h descents are massive. If the lead rider is allowed to supertuck and the avatar behind is not, that’s a recipe for disaster.

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Certainly in that case the aero effect of the supertuck would need to be made significantly less extreme as well. Plus there’s still the mystery slowdown at 0 W in sub-supertuck conditions that needs to be resolved first as well…

I still think that a good way to see if the churn effect has been resolved is if a heavier rider with a small head start can ride alone without getting caught by a pack of lighter riders with everybody coasting downhill.

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Another idea I have is to simply stop power being applied at a certain speed. Trainer difficulty means people can be adding power to the descent when they are going at crazy speeds. 70km/h seems about right, which is over 110rpm with a 53/39.

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Maybe not a problem if we end up with proper draft.

It looks like several of us have made our own models to estimate Zwift physics. Here’s what I get for a 10% descent.
A supertucking 80Kg rider will max out at 84 kph, a non-supertucking 80 Kg rider would need 620 Watts without draft to do the same speed but the draft benefit of being second at this speed is 550W so they only need to do 70W to keep up. They would have a net benefit from drafting in the 3rd or 4th row and so be able to do 0 power (non-supertuck) and still overtake - leading to churn if there isn’t autobraking to stop it even at 0W. A lighter 60Kg rider would need 250W to keep-up in the 2nd row but would just be OK at 0W in the 4th row, assuming no churn so the pack does not go above the lead rider 84kph. If the churn can be eliminated and 1.5x or double-draft enabled then it will reduce the excessive pack group speeds and help keep the pack together for all rider weights.


Seems relatively consistent with my experience, was this tested in a race? As the supertuck in a race is different to freeriding. (I think it still stands true though due to draft benefit).

It needs to work for a variety of situations. If a 60 kgs rider needs to put out 250w in a 2 rider group at 84 kph already, run the numbers again for the >90 km/h descents of Radio Tower and Bologna.

If a for real 10 year old somehow managed to hold with an A/A+ pack towards a bunch sprint finish… I’m sure many people would want to give him/her the win for their effort. IRL if this magic was going on I’d definitely try to convince the pack to do it.

The supertuck savings have not been well-tested, shifting gradients makes this difficult so only rudimentary observations from recordings, but they do look ballpark reasonable enough that I think double draft would have a great effect in keeping the pack together so long as the churn can be stopped.

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It needs double draft in those situations or it becomes very difficult to keep up. Roughly 200W for a 60Kg rider in 2nd place with double draft at 95 kph.

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Now account for 2 things:

  1. Momentary loss of draft in some corners.
  2. The biggest issue that riders have problems with when descending: what happens when the rider is pushing >200w, starts drawing level with the rider ahead so hits 0% draft. The hit they’ll take to their momentum will make it impossible to recover and they’ll be dropped.
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Their power numbers are also BS so I wouldn’t read too much in to that example.