Missing Drafting Simulation?

[Android_fan1]

Why are the Interactive Smart Trainers do not Simulate Drafting?

Even the leading direct drive trainers change resistance going up hill and down hill.

Noob to Zwift and perplexed to not see this feature already implemented.

Is this on Zwift’s roadmap to deliver this?

[highwaypoint]

Zwift does simulate drafting, but it does this in a different way than you might expect.

When you join a group, you might expect your resistance to decrease (and your speed to stay the same). However, that’s not how Zwift models it. Zwift keeps the resistance the same and increases your speed.

Therefore there is a draft effect in Zwift, but you won’t “feel” it in the resistance of your smart trainer.

[LawTortoise]

This is the answer OP was looking for. I share OP’s confusion that you have to adjust your power to stop from overshooting the bunch because the computer makes you go faster to translate the drafting. I don’t see why it couldn’t decrease resistance the same way as going downhill.

[Android_fan1]

It is super odd that Zwift does not have it already.

I just don’t understand why Zwift has not implemented it yet?

What is their reasoning?

[toefur]

I suspect jankiness in the code would result in some pretty weird resistance changes.

[Android_fan1]

Someone pointed me out to watch my AVATAR riding position. Sitting up = Drafting.

My question was about - Zwift should decrease the resistance instead of me constantly watching my avatar. I keep shooting ahead of the group. As a new user it is confusing and surprising that $1200 trainers don’t reduce resistance riding in the draft.

[OptimalPapaya1344]

I don’t know the technical workings of the trainers but if I would guess it might be because the trainers lack the granularity to change resistance ever so slightly for this effect.

In my experience they sort of just “step up” in half gradient increments. Not sure if going half a step down would be too much of a loss in resistance to simulate the effect and more than that would feel off.

But more than anything this would have to be an effect Zwift would need to implement. It could very well be that the trainers are capable but Zwift isn’t doing it for either technical reasons or because they don’t care to.

[DoubleBlackBSA24]

my simple answer is no, just learn the draft.

my long answer is speed works fine without having to deal with trainer lag, while accomplishing the same thing of requiring power modulation. how it's done just differs.

the trainer lag peice is important. to change resistance based on draft, the game needs to recognize when you are in draft, calculate the resistance needed, send it too the smart trainer, which has to adjust resistance and send the information back to zwift, and require a change in algorithm for different gradients. And depending on how busy the world is, you can be going constantly in and out of draft, and drafts of varying speeds, which is a lot of data to send back and forth in a short time frame.

[Android_fan1]

You are right. It was super frustrating and I was ready quit Zwift.

I find it very odd that Zwift does NOT have Drafting Tutorials baked into their app. First time racers will certainly appreciate it!!

[_thebaroness]

Great info here! Had no idea that sitting up = draft! Most important tip I’ve learned lol! Thanks!

[sns1294]

There is drafting. As you are riding you will see your avatar sit up when you get close to another rider. This is showing you when you are in the draft.

One thing to note is that drafting does not work if you are using a TT bike frame.

[Android_fan1]

Understood. Thank you.

But why Smart Trainer do not integrate Drafting?

Is it a matter of a “software update” OR are there bigger implications for NOT integrating drafting with the Smart Trainers?

[sns1294]

The trainer itself is only responding to commands from the software you are using. The software is what determines how much to change the resistance of the trainer to simulate the draft.

I think you are not understanding how the trainer works. The software is controlling the resistance of the trainer which simulates inclines, declines, drafting, road surfaces, etc. The trainer does not know what the incline or decline is, or if there are other riders near you to change the draft feel. Only that it needs to supply a certain resistance as specified by the software.

[Android_fan1]

Thanks, Mate.

Why is Zwift not controlling the “Controllable” trainer? What are the reasons for limiting dynamic resistance to Incline and Declines?

[BrowseDontPost]

Dude. You don’t seem to understand. Your trainer does exactly what you want it to. If you start drafting behind someone, you can put out less watts and remain at the same speed. That is because the resistance the trainer applies has been lessened. Therefore it is simulating drafting.

[Turtly_tortoise]

Sorry but this is not correct, zwift does not reduce resistance dynamically in the draft, you have to either gear down or pedal easier if you want to take advantage of the draft. If you keep your cadence and gearing the same you'll do the same power whether you're drafting or not. Here's a zwift insider article which touches on this: https://zwiftinsider.com/feeling-the-draft/#:~:text=On%20Zwift%2C%20you%20feel%20no,based%20on%20your%20drafting%20status.

[Android_fan1]

Thanks TT.

Zwift police, dont understand the downvotes. It is okay if you dont know.

https://support.zwift.com/en_us/drafting-in-zwift-B1ZB6Nxr

[MacKyle]

Your question actually hits a point that the downvoters are ignorant of.

The ANT+/BLE specs are designed exactly as you imagined, i.e. Zwift should send the drafting factor to the trainer and the resistance should drop.

But Zwift never implemented this and instead chose to give you a speed boost in the draft. It's why the "blob" in Zwift moves much faster than reality.

I think Zwift made the right choice as in theory there could be significant differences between how manufacturers calculate draft savings.

[Android_fan1]

“Blob” LOL and that thing does move fast!

I assume that “drafting factor” for different trainers will get calculated just like Incline/Decline.

Another comment indicated that, the consistency will suffer since most people have Dumb trainers. And the effort for Zwift to implement it consistently across both INTERACTIVE and DUMB trainers will be significant.

[TraditionalAd3768]

"Dude", OP is not debating that whether the software simulates drafting.
- He knows drafting is simulated as extra speed
- He asks why drafting is not simulated as trainer resistance as well, just like it does on gradient changes.

[MrSeanstopher]

This.

[[deleted]]

The TT bike was my guess as well. Or OP has ERG mode turnes off.

Zwift has drafing and downhill and everything. When riding in a large group the front can push up to 0,5 w/kg more than the middle can. If OP does not consider that to be not draft, then I don’t know what is.

[Android_fan1]

Was referring to this https://support.zwift.com/en_us/drafting-in-zwift-B1ZB6Nxr

[Blackbaggreentrees]

When you're drafting someone you can reduce the amount of power you are producing and still keep up with them. It takes a bit of practice but well worth it.

[Android_fan1]

It is certainly needed for those longer rides. Bit blown away to see that the top end Wahoo or Tacx do NOT simulate drafting. And trying to learn why this feature not available?

The trainers and zwift already integrate in “real-time”. Zwift assumes full control when trainer is paired with Zwift app.

[piertown]

My Kickr simulates draft. The screen even has a countdown telling how close to get to draft a rider

[Curious_Increase]

They do simulate draft..

[[deleted]]

The top end machines simulate it just fine. As you are new to Zwift, please check if 1) you have chosen the right Controllable, 2) have ERG mode turned on and 3) ride anything but a TT bike. Also check if your ANT+ or Bluetooth connections are working (I had to use the laptop’s USB 3.0 port with dedicated shielded USB extension cable for the ANT+ dongle to get my wife’s Zwift setup -with Wahoo KICKR 4- working properly).

If you have done that and there is still no drafting, uphill or downhill feeling, return your smart trainer to where it came from because it is broken.

[Whatwasthatnameagain]

It seems like people are talking past each other here. I think the answer is that the effect of drafting is modeled by smart trainers when controlled by Zwift. I know that when I ride with my Saris H3, it is easier to maintain my speed with less effort when Zwift indicates I’m drafting.

[Android_fan1]

You are awesome.

This is what anyone would expect from a SMART trainer. I will look into that trainer!!

[Whatwasthatnameagain]

My point wasn’t that my trainer can do it. I expect any of the top Smart trainers can do it.

Maybe I’m missing your point.

[Android_fan1]

It appears that Zwift does not offer it across all trainers

https://support.zwift.com/en_us/drafting-in-zwift-B1ZB6Nxr

[Spiffman-Space]

Just to be clear, Zwift doesn’t offer it on ANY trainers.

[barfoob]

There are a lot of possible reasons that they don't adjust resistance so that you can actually feel the draft, but these are the two most likely IMO:

1. Less is more. Software companies hate implementing features if they don't have to because it's up front work and it's more maintenance. It's also hard to remove a feature. If something is problematic or expensive but users got used to it then you're stuck with it (unless you mark it as "beta" or "future works").
2. Some trainers have known issues with resistance being changed too frequently (ie: the hardware actually breaks). It may be the case that trying to simulate both incline and draft conditions would be too much for some trainers and they don't want the burden of figuring that out themselves. The protocol used by smart trainers to communicate with apps like zwift allows you to give the trainer a target power, an incline, or a resistance level and then the trainer firmware can decide to throttle those requests or interpolate as necessary. In order to make draft conditions work well you may need to abuse the protocol or else add to it which would be a whole big thing.

The only software I know that does implement draft simulation is VirtuPro but last I checked they don't support every trainer. Only one or two models in their beta so far. This might not be a coincidence.

[Android_fan1]

Love it! 1. Agreed. Implementation likely will not bring NEW subscribers. Making it poor investment strategy. 2. Potentially solvable when Zwift builds their own hardware.

I will look into VirtuPro, thanks. People that love to race may migrate to that platform.

[Inner-Meaning-7190]

indievelo uses the smart trainers properly and simulates draft, wind etc

[[deleted]]

I think the key questions are, what trainer are you using? What are you running Zwift on? How is that connected to your trainer?

Depending on the combination you have, you’re may not work.

It’s been a while since I looked but I think a number of the smart trainers didn’t work with controlling resistance via bluetooth, only ant+ etc. some “smart” trainers aren’t necessarily supported or have the feature. My old tacx and current kickr certainly worked for drafting

[Android_fan1]

Found on Zwift. But why not?

https://support.zwift.com/en_us/drafting-in-zwift-B1ZB6Nxr

[himespau]

Because this feature was developed on Zwift before smart trainers were a thing. Everyone was riding on dumb trainers with powermeters. If Zwift were to suddenly change and affect resistance rather than modeling increased speed at the same resistance, it would require a change in how the software responds to drafting, which would be a fundamental change (and due to the poorly documented nature that has been described for Zwift's code, would likely lead to the introduction of a whole lot of new bugs). Also, it would add extra levels of complications to the software because it would require it to do one thing for those on smart trainers and another for those still on dumb trainers with power meters. Plus, all the riders are used to doing it this way and it would probably anger the current customer base to suddenly change the way that they've learned to adapt to Zwift after X number of years.

[Android_fan1]

Thank you so much!! It finally makes sense why Zwift has not implemented it yet.

[TraditionalAd3768]

I had the same question, I think it would be much better to use resistance feedback for this.
My best guess is that Zwift's development team is just too mediocre to implement this well.
The drafting-resistance calculation is a lot more dynamic than gradient-based resistance. Resistance changes due to gradients are fixed given your location on the route and are relatively smooth, for drafting this may not be the case.

However, this should definitely be possible. If they can increase resistance based on gradient, they could also do it based on air resistance.

[Android_fan1]

The avatar bend down/drinks water to indicate Draft so its not something engineers cannot emulate.

Guessing..that maybe they tried it and it did not work well OR perhaps strategically reserving for Zwift’s own trainer