Ranp test will usually overstate for riders with an above-average anaerobic contribution.
The 20 minute test will always be subject to riders’ ability to pace the effort.
Both are subject to the riders’ ability to perform on the day.
Both are only approximations as to what your FTP actually is.
These aren’t “inaccuracies” as stated in the title of the thread. They’re “differences”.
Assuming your FTP is important to you in order to calibrate training going forward, just adjust it manually to give you good workouts. If you can do a 2 × 20 at 100% and it’s pretty damn hard, but do-able … your FTP is set about right.
What three figures do you get from your 40km TT, your Ramp Test and your FTP test. I see you are set around 295w FTP for you recent workouts.
I’m not sure I understand your Ramp Test CA ride reports. From what I can see you tend to go up in minute increments until you hit around 340-360w and then rather than push on to 400w or so you flatline out for another14-15 minutes at around 320-340w and then possibly put in a final 1 minute effort. Most people when they finish the ramp test are completely spent and unable to pedal any further without dropping their power down to low ish numbers. Your ramp test should finish when you can no longer keep increasing your average watts each minute. Are you turning erg mode off and then trying to keep the highest watts going for as long as you can?
As Ben has suggested above it looks like your 20 min test FTP figure is far too low. It might be worth trying that one again .
Everyone is different but from what I have read:
the Ramp test generally produces the highest of the three figures.
The 20 minute test in the middle
The 1 hour test the lowest.
It is sometimes considered that the 20 minute test delivers an FTP around 5% above your one hour effort.
The FTP figure produced by a Zwift Ramp test from one minute best average uses 75% but it can be anything in the general range of 72 - 77%
I just did a ramp test 15min ago because there was an error since the update made on ZP. My ftp went from 270 to 234w. So I redid it, I validate 19 stars out of 30 = a 265w ftp. How come I don’t have the update done on my profile? Merci
It’s even worse the update has reduced the FTP… there is a big problem somewhere. Would it be possible to solve this problem? Please give me the correct FTP. Because we walk on the head with its updates…
Just remember zFTP is not from a ramp test it is from a series of data points on the power curve. If you want to get a proper zFTP you will have to do peak efforts at various points (i.e. 1 min , 5 min, 20 min) on the power curve.
The ramp test will only give you a peak 1 to 2 min
You can still change your FTP setpoint for your workouts within Zwift, and zFTP will be used primarily to categorize you correctly for racing purposes.
That said, I do still find it odd that Zwift still has multiple ways of calculating your FTP automatically (which I mentioned before). They have zFTP (used for race categorization - this is the number that shows in ZP) which is using a couple points along your power curve, and they have their auto-FTP logic which prompts you in game with a new FTP when you’ve done a better 20 min time than your current FTP would suggest you can.
When you do a ramp test, or another FTP test it still should update your FTP in game for the purposes of setting your workout Zones so I don’t think their update to how zFTP is calculated would really affect anything other than what category you can enter for races correct?
All this just to define my ftp for training ? What a great reward considering the effort provided on this test… (up to 420w) for a guy who weighs 64kg I can tell you I didn’t have fun. Before this test also determined the race category. I don’t know how it’s calculated but I have the impression that it’s not quite perfect yet… and that this idea of updating on ZP was validated during a good evening beer or during a spring break
Previously your race category was derived from the average of your three best 20 minute efforts in events in the last 90 days. It was not affected by the results of an FTP test, unless the FTP test was a 20 minute test done in a group workout (ie, in an event, not in a solo workout). It would never have been affected by a ramp test.