Category Enforcement Issue – Weight Bug?

I’ve had this issue for a few months now, and my interactions with Zwift Support has been less than helpful, so I’m taking it to the forums to see if anyone else has had similar issues. I’m a ZPower “B” category racer (3.51 W/kg), with above average short term power (but nothing to write home about), but have an auto-category of “A”.

Before anyone responds with explanations regarding the additional Auto-Category thresholds, I understand them. A snip of my ‘fitness’ from my-zwift-com is below. I am 82kg, with my values below:
• zFTP: 312W (3.80 W/kg) – Easily below A threshold
• zMAP: 375W (4.57 W/kg) – Easily below A threshold
• CP (from Varies between 274W (3.34 W/kg) and 294W (3.59 W/kg), depending on which model is used – Easily below A threshold

BUT… where it gets interesting is when I look at my peak power values within the above Zwift fitness data. Based on those listed W/kg, I can completely understand why it is saying I should be an A, as it has values that far exceed the A thresholds (12 min at 5.6, 20 min at 4.78, 30 min at 4.5, etc). HOWEVER, the weights associated with the 3 minute and over durations are incorrect!! The power values (watts) are correct, but my weight (as calculated by power / W/kg) drops from my 82 kg weight, and varies somewhere between 61 and 75 kg. I hate to say it, but it really makes me question the accuracy of the Zwift and/or AutoCat coding…

[My favorites above are my 1/3/23 race where I am somehow simultaneously 82 kg (5 sec) and 68 kg (5 min), and my 12/20/22 race where I am simultaneously 64 kg (20 min) and 66 kg (30 min)… huh?!?]

(For what it is worth, the ZPower results for the above races correctly capture my weight, and I record my races so it is easy to confirm my weight from those.)

So I post this in the hope that someone has seen this before and/or can provide some assistance in the matter. As I continue (and will continue) to race at my correct weight, racing as an A can be more than frustrating, especially anytime there is a sustained climb.

Appreciate any input. Thanks!

That is super weird…really crazy 5s to 1min are all with 82kg and all others are all over the kg :see_no_evil:

I hope someone from Zwift HQ will help you out looking at you ZP profile you look legit with 82kg.

Maybe a question…is someone else using your account?

[quote=“Chris Park [TV], post:1, topic:601700, username:Chris_Park2577”]
So I post this in the hope that someone has seen this before and/or can provide some assistance in the matter.

Chris, not that many posts on the forum of individual’s Peak Power numbers; two I remember are linked below. There was no follow up so I’m not aware how the issue was resolved.

Thank you Ian (and Dejan) for the quick responses! Ian, I think the posts you provided links to are exactly the issues that I am having.

In full transparency, I have helped our club run some head to head delay type races, so I have tested different rider heights/weights on a few different courses to work out approximate delay times. So although I don’t have anyone else in my household that uses my account, I have played around with different rider heights and weights. But I’ve been careful to only change those values in only those few rides, and have always been sure to change the values back to their correct values before saving the ride (and then double and triple checking before any races).

I am aware that Zwift uses all activities (those included) within their calculations, so I have been sure to keep my pure watts and W/kg for those tests below my correct peak powers and W/kg. However, I did not expect the weights to have an impact on the actual recorded peak W/kg, which I would assume should be a snapshot in time (power and weight).

What I also found perplexing is that I only used 50kg, 60kg, 70kg, and 80kg in my tests, but the back calculated weights for my 3 min to 30 min powers were 75, 68, 61, 64, and 66 kg, respectively, with no apparent correlation to the tested weights. It was also interesting that the same ride had different weights associated with it. So Zwift’s coding must have interesting assumptions included within it.

[I found similarities within both Mickael’s and John’s numbers (from the link you shared), including one of John’s rides which had four different weights associated with it, with his 30s, 1m, 3m, and 12m powers, ranging from 37-81kg, all from the same saved ride!?!]

I guess if this should all reset within 60 days, I’ll wait it out, and if I have any more tests to run, I’ll do it on my kid’s account as they don’t race :laughing:

But it would be interesting to know or understand how the weight is used within the CE calculations… Zwift??

[quote=“Chris Park [TV], post:4, topic:601700, username:Chris_Park2577”]
But it would be interesting to know or understand how the weight is used within the CE calculations… Zwift??

They had an entire thread about that not too long ago:

Thanks Claus. I had read that previously, which was my understanding of the peak power metrics being a ‘snapshot’ in time. What I find puzzling is that every one of my peak power metrics (from 5 sec to 30 min) was set in a race at 82kg, and yet the other weights are still somehow included in the final CE calculations, which seems to contradict Zwift’s post in the link you shared.

I appreciate you sharing the link, but confusion still remains :slight_smile:

[quote=“Chris Park [TV], post:4, topic:601700, username:Chris_Park2577”]
so I have tested different rider heights/weights on a few different courses to work out approximate delay times

This seem to be your problem.

Chris, I take it there’s been no variations in your weigh along that sort of magnitude?

(If mentioned elsewhere in this thread, I didn’t see it)

Hey Chris - this is how weight was detailed as being accounted for:

Doesn’t seem like that is necssarily the case so maybe @xflintx could help as he was the original article’s author?


James, Chris will answer for himself but if I may chip in with my thoughts.

There are three similar cases in this Forum, Chris’ and two others I have linked in reply to Chris above.

All three have a similar theme.
All three confirm that at some point in time weight changes have been made; 2 by users allowing younger & lighter family to have a test/fun ride, and Chris who is doing testing.

I believe that (with possibly one peak power exception) none of the Peak Power figures were set by the people riding at a lower weight.

However when the Peak Power figures are reviewed in the three users CE profile on it is clear that the weights being used to generate the associated w/kg figure do not match the weight that was used to generate the Peak Power watts.

If the average of the four Peak Power ‘arbitrary’ weights is being used to determine the average weight instead of using the actual weight then this will cause the CE category calculation to be wrong.

From Flint - “will be determined by the average weight of all weights that were in effect at the moment that certain key peak power values of the power curve were set”

From what I have seen, and in my own case, small changes to weight over the course of 60 days is being dealt with correctly in the Peak Power section and CE calculation. It appears to be where fairly large changes in weight have taken place - in 2 cases on only one occasion it seems.

I hope what I have just written makes sense.

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We can invalidate efforts if they were completed with an incorrect weight that have caused the category to change.

I’ve just been dealing with one from one of the TT Club members.

Also a polite reminder to avoid colourful language to our support team. they are only doing their job.


Ian, you nailed it exactly. In my case (and presumably Mickael’s and John’s although I didn’t check every one of theirs), all peak powers were set using 82 kg. I made sure my tests did not approach my peaks in terms of either W or W/kg.

However, my peak powers from 3 min and onward are reporting an arbitrary weight, and thus incorrect W/kg. So, based on my understanding of Flint’s post, the average weight across those metrics should be 82 kg, which would report a correct CE.

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If this message is aimed at my OP, I agree with you and my frustration is no fault of theirs (or yours). I cannot imagine the amount of emails they receive and have to deal with on a daily basis. I also understand they have the basic responses to AutoCat questions that cover 99% of those support tickets, but after being told I need to make sure my trainer is calibrated for the second time to address the above issue… I’m sure you can understand what I might be thinking :slight_smile:

I’ve asked one of our developers to take a look into this as, like you say, the power / weight numbers don’t match up.

I get the frustration, but just tone it down a little bit :wink:

:ok_hand: :+1:
Appreciate it.


According to our end, you reduced your weight to 50kg on December 17th, then increased to 70kg on the 18th and then upto 82kg on the same day. I suspect if I invalidate your data for 17+18 December, your problem will go away.


I also had done testing on Dec 11 and Jan 22 (similar weight changes I believe). However, in those instances my weight was changed to the testing weights and then back to 82kg on the same day. The Dec 17-18 was the only testing that may have spanned a night, so wonder if that trips something up?

Either way, I woke up this morning as a AutoCat B, which was a wonderful surprise, so invalidating those seems to have done the trick. I’ll make sure future testing is done on another account.

Thank you!!

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Zwift sholud probably have a warning when you shift your weight down by more than ‘x’ kg if you have a profile that has joined races recently saying something to the effect of “Hey there, as an FYI, efforts you do at this low weight will affect your race category.”


The category enforcement system currently does not account for the 0.5 w/kg penalty Zwift imposes on riders over 6 feet tall. To keep things fair the formula should include heights to account for these differences. Yes tall people are less aero, but in USAC you move up categories by winning races, not simply showing up with the watts.