FTP Road vs indoor vs TT bike

So…my FTP was set on a WattBike (after much trial and error with their settings, with me finally using my
Own pedals to match the setting to my puny output)

I’ve noticed my power output is less on the TT bike, but I’ve not done a proper FTP test on it.
However, I’ve a 25 and 10 time set on it, so could use them…but the 10 was after a day at work, hard AM swim, with some left for a brick run after.
The 25 was after a parkrun and I felt I couldn’t generate the power I wanted to. My lungs and HR were willing, my legs most certainly were not!

Any tips?

Really your FTP or 20-min Power or whatever you wish to call it is an ever changing thing in reality. As you identified, your performance is subject to how recovered/fresh you are at any given time. The key really is to stick to the same benchmark(s) and try to measure in the same circumstances each time, so they are comparable. I would use the equipment you will race on i.e. your P1 pedal PM. My 935XT will actually suggest a new FTP reading after something like a Zwift race; so if I actually did that race within a set weekly routine, that could work too.

You could also use your best 20-min power from an outdoor ride on the extensions if you so wish - the more data there the better to even it out.

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Cheers old rival!

I had a play with some of my Garmin stats last night.
Two more rides to make a decision…

…listening to “That Triathlon Show” and talking to a few club mates has shaken my belief!

From what I’ve read, if your position is good and you’re adapted to riding aero there should be a negligible difference in FTP between positions and my n=1 would tend to agree with that.
I always struggled to do intervals on the turbo above FTP in the aero position. I usually sat up for intervals and did the recoveries aero.
I then noticed on some race photos that I was holding my hands well over the end of my tri bars. I lengthened my position (an inch or so) and ever since I’ve been able to stay aero at pretty much any power level. That small change seemed to relax my whole position and allow me to pedal as comfortably as on my road bike.
I still notice a difference in power between turbo and outdoors but my suspicion is that it’s inertia related rather than position. (I don’t use the road bike on the turbo but I do ride the TT bike outdoors and don’t see any difference there)

…what are you after?

If you want an ftp to structure your indoor training (eg TrainerRoad), set up and test your ftp indoors. It’s essentially not important what the value is, as it gauges your capability in that environment and your training scales to that value.

If using it to plan your outdoor rides, you’ll need to factor in the additional cooling you get outside, and the variable weather. I think a decent 10TT is a good guide to check you FTP, I’m not bought in to outdoor testing FTP.

As for the watt bike, TT position etc. I was wondering what the difference would be so I took three ramp FTP tests - in my cold January garage in aero with fan, a few hours later upright without fan, and three hours after that again in aero.

…three days later, after a csss test swim I did final fourth test at the gym on the watt bike, warm and no fan.

I was quite surprised to find little difference between all three scenarios as I’d suffered working out at the gym in particular, and felt more worn out in aero interval training;

247 (aero/fan/cold/fresh),
260 (upright/cold),
252 (aero/cold), and
257 (upright/warm)

So you might draw conclusions but for me there so little in it as to not be concerned.


13w between the top two tests. That’s 5% which is more than what I’d ideally want.

That said, as joex said, if you’re using your FTP value to guide further training, then during those sessions most people will dial into something that they find sustainable for a race pace effort. My key sessions pre-HIM are some brick sessions with ever increasing interval durations at target race power, into an hour run with more and more time in the middle at target race pace.

If I’m honest, I know that due to the other things joex mentions (extra cooling outside for example), plus the fact that I’ll be fresher and in a race mindset, the fact I often generally struggle in those training sessions isn’t as concerning as I used to think it was. .

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I can’t get over that you did 3 FTP tests in a day. Not sure I could do 3 in a week and feel like I’d max’d out each time.


They’ll be the ramp tests I imagine

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The ramp tests are about twenty five minutes, still drive you to the point of failure/collapse but only cost about 30TSS. I feel fine after an hour, and maybe I did ‘feel’ it in the 2nd 3rd and 4th tests but it hardly changed the result.

That was another thing I wanted to see. People get so twitchy about a few watts or not feeling good for a test, needing everything to be perfect. So I thought, okay just how much variation is there in imperfect conditions? Negligible imo.

I still felt over the moon with the 260 result as it was a massive increase from my October FTP of…248 :sweat_smile: Yeah I know.

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The obvious conclusion is you are worse into a headwind :wink:

Thanks for this @stenard
I’ve been doing lots of 1.5hr to 2.5hr rides at 79-83%. Different days I’ve ended up feeling different.
The 83% ride I felt great, the 79% one, not so much!

I’ve got this afternoon (90 minutes, with some intervals) then my final brick on Sunday (1.9km swim, 105 minutes ride @ race effort, 10km run off)
If I can’t run 10km at race pace, then I know the bike effort is too hard.

Also, I hear ya on race day, when those juices are flowing and the taper has worked it’s magic!

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Dialled right into that race power this morning and ran a blinder afterwards.