That’s interesting (by the way, you’re the same age as me). I’ve just made a very similar adjustment to my own TR plan. My FTP has gone down and I’m very happy about it. Why would I say this?
Six weeks ago I did the ramp test in a gear of 50-14 and super-high cadence and scored an FTP of 275. I had a hunch straight away that it was an inflated figure not least because 275 was my end figure after the whole of last winter’s TR plan!
Anyway, immediately following this, I did SSB1LV in a slightly harder gear than this, 50-15 and, latterly in the plan, 50-16. As I’ve gone through it, I’ve realised that the sweet spot workouts have been at my threshold in reality (based on RPE and HR) and when I got to over-unders and other VO2 and threshold workouts I’ve died a death and had to reduce intensity to as low as 92% to get through the whole workout. So the conclusion is that my FTP was overstated, without any doubt.
By reducing my gearing still further (I did the last workout in 39-15) and thus making it feel more like riding up a gradient, I’ve figured that my “true” FTP is not 275 but more like 265. I’ve done the last few workouts based on this reduced FTP and confirmed that based on RPE and HR, it’s now at the correct level. As I go into SSB2LV later this week, I’m not even going to bother to ramp test, as I know 265 is correct.
I know from last year’s winter of doing four months of TR in a high gear and high cadence, when I did the first race of the season, a 20 mile mountain time trial, I did very badly indeed, because all of my training had been replicating riding on the flat, such was the simulated effect of the very high-speed high-inertia of the Kickr Snap flywheel. When I came to ride at race pace up hills, this gap in my training was brutally exposed and I got a big shock and humiliation.
I’m learning that taking a hit on my ego by accepting a lower FTP number, and by riding in a lower gear during workouts, my targeted physiological improvements (at least specifically for time trialing on anything but flat gradients) will be more effective and greater in absolute terms than if I spin a high gear all winter at a higher “indicated” FTP number.
For the record, I’m referring to training with a wheel-on trainer in ERG mode, which, as a combination, I believe, is most profoundly affected by “flywheel inertia cheating”, if we can start calling it that!
Good luck with your plan, I think you’re doing the right thing.