zwift pace partner question
#51
Senior Member
The drafting feel has come up in other online discussions in Zwift forums. I disagree that you cannot feel the draft through the pedals in Zwift, I certainly can. When going from no draft to drafting another rider (or riders) pedal resistance drops whether your speed increases or not. You can see the power number in the upper left decrease as you enter the draft, cadence is determined by avatar speed and gear. So cadence does not drop when you enter the draft. If power goes down, and cadence stays the same, torque must decrease. Lower torque means less resistance at the pedals.
When slowly closing in on a group from behind, match their speed and don't pass. Speed stays the same and you are not pedalling as hard due to the draft, cadence will not change. This is easiest to feel in a robopacer group. Ride at the front of the pack and go from 2nd row to the front and pedal resistance increases. Drop back into the group and pedal resistance decreases.
The drafting algorithm in Zwift is about half the aero effect in real life, and much less when in a very large drafting line. The maximum draft effect in Zwift is 30% power reduction even in a pack of hundreds moving at 40 kph. In real life, being in the middle of a pack of 30+ riders will decrease power by more than 50% at that speed.
When slowly closing in on a group from behind, match their speed and don't pass. Speed stays the same and you are not pedalling as hard due to the draft, cadence will not change. This is easiest to feel in a robopacer group. Ride at the front of the pack and go from 2nd row to the front and pedal resistance increases. Drop back into the group and pedal resistance decreases.
The drafting algorithm in Zwift is about half the aero effect in real life, and much less when in a very large drafting line. The maximum draft effect in Zwift is 30% power reduction even in a pack of hundreds moving at 40 kph. In real life, being in the middle of a pack of 30+ riders will decrease power by more than 50% at that speed.
#52
The drafting feel has come up in other online discussions in Zwift forums. I disagree that you cannot feel the draft through the pedals in Zwift, I certainly can. When going from no draft to drafting another rider (or riders) pedal resistance drops whether your speed increases or not. You can see the power number in the upper left decrease as you enter the draft, cadence is determined by avatar speed and gear. So cadence does not drop when you enter the draft. If power goes down, and cadence stays the same, torque must decrease. Lower torque means less resistance at the pedals.
When slowly closing in on a group from behind, match their speed and don't pass. Speed stays the same and you are not pedalling as hard due to the draft, cadence will not change. This is easiest to feel in a robopacer group. Ride at the front of the pack and go from 2nd row to the front and pedal resistance increases. Drop back into the group and pedal resistance decreases.
The drafting algorithm in Zwift is about half the aero effect in real life, and much less when in a very large drafting line. The maximum draft effect in Zwift is 30% power reduction even in a pack of hundreds moving at 40 kph. In real life, being in the middle of a pack of 30+ riders will decrease power by more than 50% at that speed.
When slowly closing in on a group from behind, match their speed and don't pass. Speed stays the same and you are not pedalling as hard due to the draft, cadence will not change. This is easiest to feel in a robopacer group. Ride at the front of the pack and go from 2nd row to the front and pedal resistance increases. Drop back into the group and pedal resistance decreases.
The drafting algorithm in Zwift is about half the aero effect in real life, and much less when in a very large drafting line. The maximum draft effect in Zwift is 30% power reduction even in a pack of hundreds moving at 40 kph. In real life, being in the middle of a pack of 30+ riders will decrease power by more than 50% at that speed.
Also what trainer are you using? My Kickr Bike is certainly not in sync with Zwift avatar speed. It actually follows Wahoo’s own power/speed model for the slope Zwift broadcasts, which is far more conservative than Zwift! They only match when climbing at relatively low speed.
Edit; Just to add that the Zwift speed / trainer cadence mismatch is most obvious on descents where, for some reason, Zwift only broadcasts 50% of the negative slope regardless of Trainer Difficulty set to 100%.
Last edited by PeteHski; 03-12-24 at 10:58 AM.
#53
Randomhead
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Okay, now I have to go sit on the floor in the basement and install netshark on my zwift computer.
FE-C has a whole list of parameters, like rider weight, height, rolling resistance, slope, and I'm too lazy to go look up the rest. The question I have is if zwift trusts the trainer manufacturers to come up with physics based on those parameters. Seems unwise to me.
FE-C has a whole list of parameters, like rider weight, height, rolling resistance, slope, and I'm too lazy to go look up the rest. The question I have is if zwift trusts the trainer manufacturers to come up with physics based on those parameters. Seems unwise to me.
#54
Full Member
This is all very interesting. What happened to the “double draft” feature that was optional when setting up group rides for a more realistic draft effect? It seemed to disappear at some point.
Also what trainer are you using? My Kickr Bike is certainly not in sync with Zwift avatar speed. It actually follows Wahoo’s own power/speed model for the slope Zwift broadcasts, which is far more conservative than Zwift! They only match when climbing at relatively low speed.
Edit; Just to add that the Zwift speed / trainer cadence mismatch is most obvious on descents where, for some reason, Zwift only broadcasts 50% of the negative slope regardless of Trainer Difficulty set to 100%.
Also what trainer are you using? My Kickr Bike is certainly not in sync with Zwift avatar speed. It actually follows Wahoo’s own power/speed model for the slope Zwift broadcasts, which is far more conservative than Zwift! They only match when climbing at relatively low speed.
Edit; Just to add that the Zwift speed / trainer cadence mismatch is most obvious on descents where, for some reason, Zwift only broadcasts 50% of the negative slope regardless of Trainer Difficulty set to 100%.
#55
Okay, now I have to go sit on the floor in the basement and install netshark on my zwift computer.
FE-C has a whole list of parameters, like rider weight, height, rolling resistance, slope, and I'm too lazy to go look up the rest. The question I have is if zwift trusts the trainer manufacturers to come up with physics based on those parameters. Seems unwise to me.
FE-C has a whole list of parameters, like rider weight, height, rolling resistance, slope, and I'm too lazy to go look up the rest. The question I have is if zwift trusts the trainer manufacturers to come up with physics based on those parameters. Seems unwise to me.
So I have a strong suspicion that Zwift simply tosses out the slope value to your trainer and leaves your trainer to provide resistance based on its own slope sim mode. When I view my trainer parameters passively in Wahoo while Zwifting, my trainer speed and Zwift speed can be quite different, especially at higher speeds.
#56
I have a Kickr Bike V1. Double draft is still available but appears in very few events, last was for one of the Zwift race series last year?. My speed in Zwift matches the riders around me for the power, slope, and in game equipment. Even though Zwift sends 50% slope to the trainer on downhills, the speed calculation uses the in game slope, e.g. descending Bologna or the radio tower. Trainer Difficulty setting has no effect on the speed calculation uphill or downhill. Zwift Insider covered all of the physics model over time. I find my speed in zwift matches very closely to real life, once you account for equipment weight, drafting, stoplights, and wind. I have power meters on my outdoor bikes for comparison.
#57
AFAIK pedal feel (resistance) is only a function of your trainer responding to the variable slope value Zwift is broadcasting to it. Drafting affects your avatar speed, but not your actual trainer resistance.
For Zwift to vary your trainer resistance with drafting would require another trainer control variable.
For Zwift to vary your trainer resistance with drafting would require another trainer control variable.
There was a single app. on the market that simulated drafting very well (maybe using that individual "speed bonus?) - it was RGT, later Wahoo RGT, which was recently discontinued due to obscure deals between Zwift and Wahoo. Maybe RGT ran some controls on every user's computer instead of server, thus, using users' PC resources to implement a very realistic personalized drafting. Briefly, I guess (I only guess) that such performance might not be technically possible due to lack of resources, if full controls are managed on the server only.
#58
Senior Member
And to think it wasn't that long ago that we could only dream of such functionality. I'm 69 years old and still remember buying my first fluid trainer at REI when I was already 50+. I did Computrainer classes at an indoor studio over 20 years ago and that setup was so high tech at the time but so expensive that only a well endowed studio could afford it. We could actually ride against each other!! I bought my first power meter when I was 63, and how cool was that? I could actually track what I was doing in The Sufferfest and not using their guesstimate, and my real power was about 50 watts lower. And then I got my Kickr Core and got on Zwift, maybe 5 years ago, when prices on a smart trainer broke the $1k barrier. I've seen everything improve over the last 5 years, but it still isn't perfect.
#59
I guess it can be done without that: if a complex algorithm controls very close your position around the pack, then it can give you a personalized variable "bonus" in speed depending on your position. You would feel that as a reduction in power, because you will ease up the force to stay in the pack. It is somehow similar with real life. But if the whole controls run on the server, it might not have resources to control those complex parameters for each of the tens thousands riders that ride in the same time on Zwift (not to mention network data transmission delays). Therefore, I guess that in Zwift the server simplifies and gives to everybody a rough speed bonus (not personalized) around a pack, regardless their position as leaders or "drafters". This is far from real drafting.
There was a single app. on the market that simulated drafting very well (maybe using that individual "speed bonus?) - it was RGT, later Wahoo RGT, which was recently discontinued due to obscure deals between Zwift and Wahoo. Maybe RGT ran some controls on every user's computer instead of server, thus, using users' PC resources to implement a very realistic personalized drafting. Briefly, I guess (I only guess) that such performance might not be technically possible due to lack of resources, if full controls are managed on the server only.
There was a single app. on the market that simulated drafting very well (maybe using that individual "speed bonus?) - it was RGT, later Wahoo RGT, which was recently discontinued due to obscure deals between Zwift and Wahoo. Maybe RGT ran some controls on every user's computer instead of server, thus, using users' PC resources to implement a very realistic personalized drafting. Briefly, I guess (I only guess) that such performance might not be technically possible due to lack of resources, if full controls are managed on the server only.
#60
Senior Member
The question is whether or not drafting in Zwift actually has any real dynamic effect on your trainer resistance. Do you feel an increase in pedal resistance as you move out of the draft like you would IRL? Or does your on-screen avatar simply slow down, with no change in pedal resistance? I think it’s the latter. But if trainer resistance is changing dynamically then there has to be a control variable sent by Zwift to action it. The only dynamic resistance change I feel on Zwift is whenever the slope changes. I don’t feel any change in resistance when moving in or out of the draft. My avatar simply speeds up or slows down. Of course I can reduce my power output in the draft to maintain position, but that is not the same thing.
https://zwiftinsider.com/feeling-the-draft/
https://zwiftinsider.com/zwift-drafting/
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#61
Full Member
The question is whether or not drafting in Zwift actually has any real dynamic effect on your trainer resistance. Do you feel an increase in pedal resistance as you move out of the draft like you would IRL? Or does your on-screen avatar simply slow down, with no change in pedal resistance? I think it’s the latter. But if trainer resistance is changing dynamically then there has to be a control variable sent by Zwift to action it. The only dynamic resistance change I feel on Zwift is whenever the slope changes. I don’t feel any change in resistance when moving in or out of the draft. My avatar simply speeds up or slows down. Of course I can reduce my power output in the draft to maintain position, but that is not the same thing.
#62
Senior Member
Let's look at it this way, or actually, let's close our eyes. If you close your eyes during a Zwift session you would never know you were drafting. If you maintain your power and cadence you will blow right by the rider. It is only seeing the rider, seeing a position change and seeing your speed, cadence and power that you know you are drafting. If you could close your eyes when riding outdoors, you would suddenly feel an easing of the wind resistance when you started drafting and feel like you were being pulled along.
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#63
If you speed up entering the draft your cadence goes up, resistance stays the same so your power increases. If you reduce power by keeping the the same cadence and lowering torque then you should feel that. Exactly what happens in real life. Whether you perceive the draft effect it is on you, because the effect is there. When Schlange was asked the same question why he did not perceive the draft effect, he had no answer and acknowledged that the power decrease in the draft has to exist.
There was one article discussing how Zwift could introduce a draft resistance factor as there is a “draft factor” included in the trainer comms profile, although it is only included in the ANT+ profile and not in the BT profile. They mentioned that some other apps are using this draft control parameter, but not Zwift.
I think it’s all just a mind game. When you enter the draft you know you can back off the power and of course then it feels easier. But if you deliberately enter the draft at a steady power and cadence, nothing changes other than your virtual avatar speed. I tried it multiple times to confirm. The draft itself actually allows a power window within which you stick to the wheel in front. So you can back off the power more than you might think before losing the wheel and adding more power does nothing until you exceed the upper end of the draft window and move through the rider in front. To be honest it all feels quite natural most of the time.
#64
https://zwiftinsider.com/feeling-the-draft/
A few snippets from the above link:-
“On Zwift, you feel no change, as resistance does not change based on your drafting status.”
“Ideally, Zwift would be able to send a simple “drafting factor” to our smart trainers, just as they send wind resistance, slope, track resistance, weight, and other parameters.”
“smart trainers use two different wireless protocols: ANT+ FE-C (ANT) and Bluetooth Smart FTMS (Bluetooth). The ANT specification does include a drafting factor. But the Bluetooth specification does not.”
The last comment is interesting and suggests that it would be very easy for Zwift to add a drafting effect to trainer resistance for users with an ANT connection. But it appears that they don’t currently use this parameter.
#65
Senior Member
Most trainers support both ANT+ and BT these days, but not everybody has an ANT+ dongle. They are cheap enough though that if Zwift were to support it you could just add one to your setup if you don't already have it.
#66
Just to complicate things, I read that Zwift sends rider weight over a BT connection but not with ANT connection. So resistance is not weight corrected when using ANT.
#67
Senior Member
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#68
This was fixed back in 2018: https://zwiftinsider.com/update-1-0-29337/ (unless it was broken again later)