I’m sure this has come up plenty of times but I think my case might be slightly different.
I’m training for 10mile tt’s next season. I’m new to TT and tr but not new to structured training. I’ve been training with power for about 2 years.
My FTP before tr was 260 after a couple of months off training but with regular riding. Tested with the 20min Zwift test.
I started training on tr using my TT bike with the FTP reduced by 10% for a rough starting point. I had only tested the week before and didn’t want to do another so soon. I did the base 1 and am doing build now. It’s week 11 of the program
Today I did a ramp test on my road bike as the TT bike is currently out of action and got 250.
I definitely didn’t leave anything out on the road. I almost passed out at the end of the test.
I did do one effort outdoors last week to test my legs and easily beat my pb on a short local hill climb. Not useful for time trialing though.
The only thing I’ve changed on the program is switching out the Sunday ride with a club ride. I also had week off about 4 weeks ago with a head cold
So what’s going on? Just a bad day? The Sunday session is more important than I thought? Something else? Don’t even worry about it?
20 minute test vs ramp test - they will give slightly different results. It’s important to try and use a consistent testing protocol (be it 2x8, 20 min, or ramp - and there’s differences between the Zwift and TR ramps).
With the ramp, it’s based on 75% (IIRC) your peak 1 min power which according to TrainerRoad’s data is a good estimate for most users (and the shorter test has a lot of advantages in terms of fatigue, frequency and repeatability of the test). However the correlation will be on a bell curve and some people will naturally test higher or lower by one test method than another.
So for now I would not worry about it, keep training (especially if you are using AT - that can correct for FTP to some extent by making workouts harder or easier), and make sure you use the same test protocol again next time. Any time you’re changing test protocol you’re no longer comparing apples with apples (same for setup changes, but sounds like you know about the drop on a TT bike already). I certainly wouldn’t be worried after one test with a new protocol.
If you’re TT’er then I’d expect a reduced ramp test result. Ramp test is more of a test of your VO2 not Threshold. Threshold generally is a TT’ers strength so expect a higher result from a 20 min test as it’s testing threshold power.
Don’t compare ramp tests to longer tests.
Don’t consider either test metric your FTP and you won’t be as concerned. As long as you are in ballpark and using AT, you will be A ok.
You’ll find out what your FTP is by progressing through threshold workouts. You want them hard - as in, can do more, don’t want more.
The only way to know what your FTP is, is to do hard sustained rides and dial into it. But that doesn’t mean the only way to get a productive training plan is to nail your FTP.
And with experience TTing and training in that threshold zone a lot, you’ll learn the sensations.