Yesterday, Zwift enabled an adjustment/fix for drafting which will be particularly noticeable on descents. Here’s what was posted on their forum:
We’ve made an adjustment/fix to the drafting effect that’s now enabled for game version 1.102 and newer. Here’s how you can check what version you’re using.
Up until now our drafting algorithm didn’t properly use road incline/decline percentage in the equations and this change will fix the issue. The steeper the climb or descent, the more the change will be noticeable.
The end result is:
- You’ll be able to stay with riders just ahead on steep climbs with slightly less effort than before.
- Staying in the draft behind a rider while going downhill will be much easier than before – you should be able to draft supertucked riders easily now.
- Pack speeds on the downhills will be slightly higher than before in general, on the order of 10-15% on steeper descents.
- Drafting on flat roads is unchanged, and speeds while riding solo are also unaffected.
- For group rides and races making it to the top of a climb with the group is more important than before because of the points above
What Was Fixed?
Zwift says, “Up until now our drafting algorithm didn’t properly use road incline/decline percentage in the equations and this change will fix the issue.” So what was actually broken (and fixed)?
It’s an interesting little bug that is easy to understand. In Zwift, as in real life, every rider casts a draft “shadow” behind them as they cut through the wind. If you’re in another rider’s draft shadow, you’re hitting less air resistance, making it easier to move forward. Cycling 101.
But Zwift’s algorithm was calculating perfectly horizontal draft shadows regardless of road pitch. This works fine on flattish roads, but as the gradients get steeper, horizontal draft shadows will impact riders behind less and less! Zwift confirmed with me that the draft shadows now now extend parallel to the slope of the draft-giving rider.
How Does It Feel?
In my tests, the results of Zwift’s draft update are exactly as described above. It’s particularly noticeable on descents, where the draft is simply stronger than it used to be. Riders used to have to put out some power to hold the wheel of a supertucking rider, but you can now sit on that wheel at 0W, because the draft off that supertucking rider is stronger.
So while supertuck is still a fast and easy way to descend steeper hills, its utility as a weapon of attack has been blunted.
One important result of this change is that it’s now easier for lightweight riders to hold a good pack position on descents, as they sit in the stronger draft.
Coming Soon: More Tests
It’s time for me to run fresh tests and update this post, which showed how much power it took to sit on another rider’s wheel while they were descending in the supertuck or at certain wattage, in race events or group rides.
Questions or Comments?
Go do a test ride or two, then report back your thoughts on the updated draft for climbing and descending. Chime in on the Zwift forum topic, or comment below!
Thank you for the update Eric! One question ahead of this ZRL TTT: is it the fix you mentioned in the guide for Week 4?
(Heavier riders, take heart: Zwift knows about this issue, and internal sources tell me a change is planned soon to make escalators perform much more uniformly across various riders. Light riders: enjoy the escalators while you still can! 😁)
You mean there are people that actually enjoy those new escalators? 😛😂
Nope. That’s a different fix!
This seems like a good logical move. Still waiting for rider size and weight to affect things too though as that is also logical
But rider size and weight DO affect things…?
He probably means that bigger riders should provide more draft, which is not the case currently, right?
Correct, MH. That is not the case currently: https://zwiftinsider.com/rider-size-draft/
If lighter riders would give less draft, the Burrito wouldn’t murder lighter riders vs heavier riders
IRL, I like getting on the wheel of that one dude who is 6’4″ weighs about 250lbs and is fairly strong.
‘Free’ ride….take it easy….
😉
I think it was meant to be “when drafting”, as bigger and heavier riders should produce a bigger draft shadow than weenies.
a 100kg rider slowly was riding the group off his wheel in a flat race today, and i had to work like F just to stay on him. (im 70kg)
I was told somewhere that the draft from behind a little rider is the same as a big rider which didnt make sense
Perhaps they should improve weight to include body fat. (As long as they don’t use the poor BMI estimator.) The relative fat mass (RFM) measurements would be at least a step in the correct direction.
I wish available electrical conductivity scales were more accurate for body fat. That would make this easy if those were more accurate.
Assume a rather significant IRL performance difference between big and strong -vs- big and fat.
Finally!!!! No more need for lightweight riders put 300 or more watts just to follow (many times in vain) heavy riders on descents.
Today is a good day 🍻
Unless you’re a heavy rider. 😔
I’d like to see three things – more realistic draft, corner speed limits, and a limit to how many riders you can pass when the pack is dense.
I want to have the draft extend past 2 riders, meaning if you’re 10 riders back you get a better draft. There’s a Zwiftinsider article with a link showing that the draft benefits are up to 95% savings in real life, but those riders are buried in the field. Right now the draft only benefits two riders so it’s very difficult for a light rider to stay with a big, fast group on a flat road. A higher draft “addition” would keep big groups together better rather than splitting them up. It would allow light riders to sit in without holding a high w/kg. It would make climbs more important. It also reflects reality just a bit better. You could have a wider range of rider power levels stay together. I suspect that with better draft the fast starts would go away because the riders sitting 10-20 riders back will get a free ride. It becomes a sharper race, allowing lower FTP riders to mix it up with much higher FTP riders.
(For me this is the biggest difference between Zwift and real life – I’ve won and placed in Cat 3 races averaging well under 200w (place 3rd at 155w, win at about 190w), using every trick I know to be a more efficient rider. In Zwift I’m a D that can sprint. With a proper full-pack draft, I’d suspect I could race Cs instead of going full anaerobic for the first minute and get shelled. I still think Bs would be a stretch. I don’t think I’d do as well but it would make for much more interesting racing.)
I also want to have “corner speed limits” so a hairpin can’t be taken at more than, say, 35 kph. Or a 90 deg corner at more than 50kph. This would encourage a bit of an accordion effect, which would make positioning a bit more important. This especially for any twisty corner kind of course like the Crit course, or downhill hairpins approaching the finish (like Watopia beach banner coming off the default KOM hill). Narrow roads, like those in Neokyo or the Castle Crit or some of the other “narrow” feeling areas could be lower, like 40kph for a 90 degree. Dirt could be even less, like 30kph. I don’t know what’s realistic on dirt actually.
(This wouldn’t really help a hill climber but it would help the break riders trying to get away from the sprinters. Break riders have a lower top speed since it has to be sustainable. Part of the idea of a break vs sprinter is that the break rider can hold a steady speed, the sprinter has to close using bursts of speed. But in the current environment, a sprinter can blast through a corner at whatever sprint speed, basically negating that corner. In real life they’d have to ease for a few seconds, giving the speed benefit to the break rider.)
Finally I want to see some solidness in the riders, although there’s an element of that already. Meaning going into a hairpin corner, you can’t just ride through everyone to get to the front. Otherwise my accordion thoughts would reduce down to everyone sprinting for the corner, mushing together, and then who knows what would happen. But if there’s a limit, like maybe you can pass 10 riders a second in a dense pack, then you need to be 30 riders back at 4-5 seconds before the corner. Being 100 riders back wouldn’t work. This would keep sprinters from sitting in 10-20 rows back, doing 5% watts of the rider at the front, then sprinting at the end. THey’d have to start moving up etc, just like in real life.
(I say there’s an element to the solidness because you can’t have all 40 riders in a pack in 2 meters of road. However if you’re at the very back before a sprint, it’s just a matter of launching at the appropriate time to get the 2-person-worth-of-draft for the entire time you’re in the pack, no worries about getting hung up in the field. With a passing limit per second it would make things quite hard to sprint from the back.)
I have no idea how such ideas would be incorporated into the Zwift world. I don’t know how such variables would affect race outcome. It would be interesting to test though.
Would love speed limit when cornering, like the hairpin in London where speed is reduced to 33 kmh. Also increased rolling resistance when raining would be groovy. Imagine the gravel turning into wet mud.
Muddy rolling resistance is interesting! Imagine a rainy muddy gravel race. Could be brutal.
Those are insightful observations. Pack Dynamics in Zwift feels broken across the board. With the tools available today, especially AI, every aspect could be analyzed and improved — yet it’s unclear what direction the developers are taking.
Significant changes in way things are going on descents will effectively RUIN heavier riders efforts COMPLETELY.
Otherwise Zwift must do something with the fact that basically w/kgs beat raw watts on flats (you may produce up to 50% more watts and still be outrunned by higher w/kg
So it’s a question of game “balance”. And the key weapon is ligher riders dominance on any noticeable gradient.
I think the FLAT drafting dynamics are pretty good actually. Riders who put out more pure watts do have an easier time on flats (If you compare a 75kg rider and 90kg rider doing the same w/kg, the 90kg rider will go faster).
If anything, I’d say lighter riders are more heavily punished on flats and downhills because drafting effect (and the size of the draft) is the same regardless of rider size/weight.
The update for downhills will be a great improvement. It was pretty stupid when I was getting dropped by a rider in a supertuck when I’m putting out 300 watts behind them downhill.
Zwift really should’ve made their own post about this as clear as this, theirs was very muddled/odd sounding. Cheers for the clarification of what’s going on 👍
No reward for those of us who made 104 weeks/2year streaks
A 2 year kit would be great please
Maybe a teeny tiny violin would suit you better
Yes, to be played by my scoty mascot
The true reward is your improved fitness — no need for gimmicks or childish distractions like ‘Scotty in the pocket.’
And the friends made along the way. 😉
As a lighter rider I’m hoping this helps me out. When riding with robopacers I find I have to work a medium amount on climbs, then hard on the flats, and extremely hard on descents.
It’s the opposite for me. 😀
errr… you never rode with robopacers when they first came out did you!!!??? that was a royal mess. the robo would ride so slow going up, and then like a rocket downhill.
This will not help a solo breakaway. i’m curious to see how this will operate with 2 or 3 riders in a breakaway versus a pack…
Good that the fix the draft. But I don’t get why they would increase the speed of a pack on the downhill. Usually that is the one place a breakaway rider can increase the gap to a pack in real life because it is much harder to do proper relays on a decent.
It seems this update makes it again harder for a breakaway rider to stay away, resulting in more bunch sprints.
It’s not that Zwift purposely increased downhill speeds. It’s that the draft bug fix naturally leads to slightly increased downhill speeds, probably because some riders may slingshot through the pack because of the draft and off the front at higher speeds…
Tha ok but Zwift should also put a caution factor in place that reduces draft in downhills (or better: braking or enforcing a minimum distance from each other if riders get too close). Because you can’t assume a super tight bunch hammering a downhill with perfect draft…in real life that would be dangerous like a suicide mission.
Timely. There was a November 23rd GCN video: Why Are There So Many Deaths in Road Racing?
Had an interesting collection of bike care crash video segments. Some of them seemed on the suicidal side… Curves near the bottom of the hill with tight bunches were scary.
But somehow, curves on flats with crashes had the most crash videos. Those had to be human error…
Further evidence to support many people’s hypothesis that no one at Zwift actually rides a bike outside faster than 15km/h.
Go for a ride with Eric Min (CEO) and Steve Beckett (VP of Marketing) and report back on your findings… 😀
I’ve ridden with plenty of strong/fast folks from ZHQ.
But to your point – I think this is evidence of what happens when you don’t have a live draft meter in game. Harder to spot issues like this!
It was raised a few years ago when they stopped the supertuck in the draft. People noticed that you could still supertuck close behind some down from the radio tower.
The sauce draft gauge helps spot it, the New York escalators made very steep sections more common and easier to get to so more people noticed that you got no draft on them
Indeed before the fix I noticed there was zero draft going down -19% in NYC and was wondering was sort of coding would mess that up specifically on those slopes.
min and beckett dont code.
I never said they did. 😄
Has anyone noticed the Tiny Races seem to ignore a rider’s racing score currently. I have been below 350 now for the last 8 rides and it has kept me stuck in the 350-500 group. The score mattered 3 weeks ago. A 342 let me ride in the 200-350, and if I did too well ( like 2 top 10 rides) it would justifiably promote me to 350-500. This level will quickly reduce my score below 350, because I can only get top 75 scores.
Tiny Races are now based on your 30-day best score. Not your current score.
Would be interesting to see if and how much this will impact rolling sections where I as a light rider need to fight hard to stay with the group. Titans Groove, Bell Lap, etc
Is super tuck a benefit when bikes are neutralised? e.g. if using a Road Bike in a TT event when a TT bike will not supertuck?
Yes. If your avatar is visually supertucking, you’re benefiting.
Still waiting on Zwift physics to actually mimic real conditions better. Though it would cause all the people who’s annual stats rely on banging out sub-5 centuries on less than 150w to throw a tantrum. 🙃
With real world physics you could do it below 100w in a group. Zwift physics *limits* draft in an attempt to give breaks a chance versus just sitting in the bunch.
sub-5 century is doable solo at 180w outside, for someone taller and bigger than average.
as a bigger guy, this change is going to be tough. But if I attack hard at the top of a descent, how far ahead do I need to be such that my chasers aren’t in my draft?
I use Sauce for this, but I aim for more than a second lead which is ofcourse different in meters for the speed you are going, but I would say 20 meters perhaps?
Now we need the hard coded limit of 50% of the descent gradient (when using 100% trainer difficulty) removed and equal to the ascending simulation.
Thanks for the explanation. This seems like a pretty big bug to have been sitting out there for so long!
So, they nerfed heavy rider’s one big advantage. Great. 😉
Cool, another way for lighter riders to have an easier time in game.
overall zwift has buffed this in favor of heavy people – because heavy people QQ louder.
This fits in the long run that Zwift just want to give light riders as much advantages as possible. Their w/kg-Algo is just bullshit and this can be seen on every flat course. Riders who would never stay in a pack outdoors (because they are 50kg or lighter) easily cruising in high absolut watt packs…it is just unrealistic, but I guess this is an order from the highes person in Zwift HQ.
I got beaten by someone who did 280W for 35 minutes while I did 345W on a pan flat course itt (so no draft) and everyone had fixed bikes. The CDA benefit of the smaller/lighter but significant weaker rider is insane. He would have not beaten me by almost 2 minutes while doing 65W less then me on a flat course for sure!
It’s like zwift is calculating that everyone is always riding in upwards position and so not in a aero position at all. That might explain the much better CDA for the dude. But newsflash … we can aero as well!
Good news, but I’m still waiting for a fix so you can really feel the draft in the pedal resistance, just like in real life
Let’s now address the claim that just a couple of centimeters make an insane difference in CdA, as if longer/taller riders are incapable of getting into an aero position and are always sitting upright.
Wow it only took them the entire 4 years I’ve been using Zwift to finally figure out and fix why lighter riders drop like flies from the pack on descents
I can’t believe , zwift is becoming more friendly to lighter rider.
Short rider checking in:
previously I would get easily dropped on down hills if I was not paying attention to the robot. Keeping up with robopacers on a downhill required focused effort.
as of this morning I can report I now can pedal the Same w/kg as the robot and keep up in the downhill now
I think this now-fixed bug is partly to blame for riders preferring and Zwift implementing the rather large power variation (80% to 110%) for robopacers. Hopefully Zwift will realize this and reduce or eliminate that variation so that those of us who want to ride steady can actually do so with robopacers.
I understand this perspective. However, I enjoy the slight variation in effort with robot pacers. Zwift already offers a way to have steady workouts with ERG mode workouts (https://zwiftinsider.com/creating-custom-workouts/). Having small variations in effort based on terrain adds a nice variety to what is mostly a steady effort; a bit more like outdoor riding. I honestly hope they do not alter robot pacer variation.
I understand this perspective. However, I enjoy steady efforts with robopacers. Zwift already offers endless ways to have varied workouts with free riding and workouts. Having steady group rides adds a nice variety because pretty much everything else in Zwift is varied (workouts included); steady is a bit more like people who train seriously ride outside. I honestly hope they reevaluate.
I’m wondering how much to the variation has to do with the Tron bike performance. (pace bots use Tron bikes). Not great uphill, but really fast otherwise.
I don’t usually use the Tron bike since it feels so sluggish uphill. So with the pace bots I tend get ahead on the uphills and tend to fall behind on the downhills.
Not so sure about this update.. group speed downhill did not seem wrong to me, draft indeed did. But I rather feel the simulation of downhill speed in Zwift is not very accurate for heavy high watt riders. And it has been about two years ago, before all the PD updates it felt more realistic. At least that´s how I remember it.
It is now a lot harder for me (at 85kg) to get to 100kph+ on a descent like radio tower. Outdoors on a comparable descent I get to 100kph without having to unleash a sprint (that I would not dare to do on such a decline) Certainly none of my road bikes is comparable to what I can choose in Zwift either, so I would expect such a bike to perform even better. Yes, downhill feels too slow in Zwift! I have enough data from outdoor rides to confirm this. In a direct comparison down ADZ with a 15kg ligher rider the difference seemed rather minor, a lot less than it should be.
Zwift does seem to be a bit slower than IRL on straight downhills, but it more than makes up for it in the corners.
Nice to read that “One important result of this change is that it’s now easier for lightweight riders to hold a good pack position on descents, as they sit in the stronger draft.” because it was really ridiculous for lightweight riders and youth riders
Not sure if this was a bug, or a fix, but at last weekend’s Nov Gran Fondo ride, there was multiple avatars going into supertuck, even within a pack…just like the old days. Wish I would have taken some video.
After a couple of months testing. I noticed a lot less breakaways leading to a succes.
I there is a downhill in the last bit of the race, the pack speeds go so high that the break-away has no chance.
I do agree that lightweight riders should be able to stay in the draft of the pack.
Good that this bug is fixed by increasing the draft.
But the downside is that also the pack speed is increased. So riders that are alone in supertuck, get caught back too quickly.
Maybe this can be solved by decreasing the CDA of the supertucker. (also for taller riders I think IRL CDA during supertuck should be closer to the CDA of small rider)
Or maybe decreasing CDA depending how long you are in supertuck position. This will take away the overshooting effect in packs.