As Paul suggests seeing your Fitness Metrics and Peak Power figures will help explain.
You are using your ZwiftPower current weight of 71kg but you will have set some of your best Peak Power figures at a weight of 69kg. The calculation uses an average of your weight at the time you set some of the Peak Power figures.
Your race on 10th September included your recent best 6min to 11min power. This race dropped out of your 90 day window this past week. Losing good 6-11 minute ( possibly 6-8 minute) Peak Power figures will have increased your zFTP by 1-2 watts and that’s all that was needed to possibly/probably take you over 3.36w/kg and into B cat.
CE calculation works on maximum efforts. IMO You need to re-set your 6-8 minute Peak Power figures by putting in a max 6 minute effort (@260w), fully recover and then put in a max 8 minute effort (@255w). Doesn’t have to be in a race and can be done over two days if that helps.
Thanks. I thought it may be something to do with 90 days as I hadn’t done anything for a week or so, but moved up. It still says my zftp is 233. Weird that losing a good short.term effort can increase my FTP score, you would think better scores means better FTP, but it seems.more complicated than I realise
Only Zwift can answer that one. It’s not accurate information, and any zFTP related number they put there does not capture the complexity of CE which includes zMAP and Watt floors. They would have to replace it with something that says “read the FAQ”.
Ok, cool. Thanks everyone for your replies. I think, as you say I just need to get on with it rather than worrying about the algorithm or whatever is behind it!
Many of the other datapoiints in your profile suggest your in-game weight was (at least when it was recorded?) 69kg. So this could be part of what’s going on as well.
Just to update on this - following advice above I did a hard 6 minute effort and have been put back to C. I still don’t really understand, but the advice provided did rectify my profile
Your 90days reset, I am in the same boat, I had one good effort back on Sept 25 and it put me into B from C. My 90days expires in a couple days. so looking forward to that