There's been some discussion on this recently:
https://forum.slowtwitch.com/...%20position#p7445346
https://forum.slowtwitch.com/...%20position#p7434916

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Benjamin Deal - Professional - Instagram - TriRig - Lodi Cyclery
Deals on Wheels - Results, schedule, videos, sponsors

If you lost 80ftp in the TT position then i would examine your position. It must be uncomfortable if you are losing 30%+ of your power, even if you dont train in the position often. That makes no sense

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Strava

Yeah I thought it was strange too but at the time of the tri bike FTP test I had barely ridden the bike. I know my position also needs a lot of work but waiting to get a new bike for that. Just trying to see what the normal difference should be.

Well, its weird because im picturing you sitting upright on the tt bike, pushing a comfortable 230w in z2, then you go into the tt position and bam, now youre in high threshold?

You can see my concern there

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Strava

When I used to test FTP I found about a 10% drop going from road to tri bike. 30% seems extreme.

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Favorite Gear: Dimond | Cadex | Desoto Sport | Hoka One One

To add some more context here, the 310 test was taken outdoors with crank based PM when I was cycling almost everyday and probably in my best cycling shape. The Tri bike test was on zwift about two months later a few weeks after doing my first 70.3. Wanted to see what range I should be aiming for so thanks for the insight guys. Definitely need to do more training on the tri bike.

You probaly shouldn't even worry about the comparison then based on all those factors.

Unless your 70.3 was some B level event, it's pretty pointless to take an ftp number after said event, if you properly "recovered" etc. (IE- lost fitness from your "race fitness").

So what I'm saying is you have a very high percentage of "user error" in your comparision.

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Brooks Doughtie, M.S.
Exercise Physiology
-USAT Level II

What kind of test? I'm guessing with that kind of discrepancy you did a 20 minute test outdoors on a road bike and are comparing that to a ramp test indoors in the aerobars.

I've updated the topic I created.

For this topic:
-Are the measuring instruments the same for both bikes: same smart trainer....etc...
-80w loss at that road bike power to TT is mammoth
-What ratio of road to TT do you do? I've known folks on my bike team that bought TT bikes and were initially not very pleased. They thought it was "buy and fly" deal. Nope. That super upright road bike power was suddenly piddly puny in TT aero.

For TT the losses can be big. The position is often super aggressive since the racing is shorter and you're not running.

Other thing is, ramp tests can be shit for TT. You'll get this big number for road and then some tiny number for TT.

IMHO, the best way to get started for TT is to do either an outdoor or indoor 10mi or 25mi TT. Whatever you can handle physically and mentally.

End of fall I did both. 25mi TT one week and 10mi TT the next. Having that data has let me set very good workouts for the TT bike.

I once every few weeks storm up Epic KOM for 20min anyway on the road bike on Zwift, so I get that number anyway.

So, essentially........I now maintain different workout ftp's for the Trainingpeaks workouts and Zwift workouts. I will generate less TSS and different time in zones on TT since I keep mine setup for the road bike ftp.............but it seems to workout now.

And a better testing protocol if you expect to obtain any useful information from it.

Would love to see screenshot of data for both tests, including HR data if possible.

Mine is roughly 8-10% different, I think, though I have not formally tested.

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Dr. Alex Harrison | Founder & CEO | Sport Physiology & Performance PhD
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im far from an elite cyclist, but i usually ftp in road bike position then when doing workouts on the tri bike ill knock off 10%. i typically will bump the resistance up a touch from that (just going off RPE) so im going to echo what most say, i personally am around 8-10% lower in TT than road position.

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80/20 Endurance Ambassador