That’s interesting. I think I made this point earlier, but I’ll make it again.
I use a Kinetic Rock N Roll trainer. My bike sways side to side as much as it needs to. I have only ever used this trainer (new to cycling).
My indoor and outdoor power is about the same, but a slight tip to indoor power being HIGHER which I think is because you have less peripheral distractions indoors; you can just focus on hitting the power and don’t need to be concerned with avoiding potholes, oncoming cars etc etc.
Perhaps it is the fact my bike rocks side to side, very similar to outside? 
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My point. 
I’ve not had major differences inside v outside. But do almost all indoor work on emotion rollers. It’s easier to do the longer VO2max intervals outside but I’m convinced that is mostly mental. $0.02
All I know is, if I am fatigued and unsure if I will be able to complete a workout I take it outside and find I can complete it no dramas. RPE is absolutely lower outside and I can push higher average watts for the interval as a result. So I wonder if I shouldn’t do all my workouts outside. Higher wattage has to mean higher return for the effort.
The big upside is when I come to race, I feel like I am flying and smash big numbers! Still haven’t found an answer to that question.
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Is there any way how to tweak outside workouts to use my outside FTP? On TR, garmin connect or even on the Garmin Edge 820?
Someone mentioned to click on “little pen”…
This question has baffled me for awhile, and I wish there were some real scientific studies to see what the real effect of a discrepancy is. I definitely have a pretty big difference inside vs outside…though I don’t know the exact number because haven’t tested with the same bike/power meter within a short period of time.
I do wonder though that if you have a significantly lower inside FTP, are you actually stressing your body enough to create ideal adaptation if the majority of your riding inside. If you’re capable of pushing 300 watts for an hour outside, and 250 watts inside…and then you spend the majority of your time only pushing your muscles relative to a 250 watt inside FTP, even if the RPE/HR is hard, are you truly pushing yourself and making the gains you should be? OR…are you just getting better at riding inside. Why is it different from someone who can squat 300lbs only squatting 250lbs all the time, or basing their workouts off a lower 1 rep max? Or someone who can run a 5 minute mile basing all their workouts off a 6min mile max. Or maybe it doesn’t matter, since the biggest factor is time on bike and accumulating some amount of stress.
It’d be cool if some study tracked cyclists over a period of 6 months or something, where inside/outside FTP was calculated for both…then half the group did exclusively inside workouts, half did exclusively outside workouts of exactly the same structure…and then inside/outside FTP tests were done at the end. If the group that road exclusively inside raised their inside FTP’s by 5%, did that translate directly to a 5% outside FTP increase? Did the group that trained outside, but had a big inside/outside FTP differential raise their FTP’s by more outside as compared to the group that road inside and had big inside/outside differentials. Obviously it translates, or we all wouldn’t be getting faster and guys like lionel sanders wouldn’t exist…but the differential just begs the question as to if we’re selling ourselves short by training inside.
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I wish to know why too. I’ve tried so many things to try and close that gap. Whether I am getting the expected adaptations is my biggest concern too because my difference is so big that for a threshold interval indoors, I’m riding at my outdoors zone 3. So I end up doing all my intervals outdoors.
Interesting discussion. I’m stronger indoors vs outdoors. For me, that makes sense, as indoors, all your focus goes on pushing the pedals. Whereas outside, you have to balance the bike, scan for obstacles, make decisions based on other road users etcetera.
You lot with a lower indoor FTP are weird 
All I can add is I use a Rock n Roll indoor trainer. Maybe that lateral movement is crucial to performing like outside 
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Love your squatting analogy. If the squat bar was somehow sticky against something, like your were dragging it against the rack without knowing it (weight reads lower but overall stimulus is there), my guess is that compares to the trainer inertia issue, and is a big part of why the discrepancies vary so widely (different trainers between everyone).
Personally, same bike and power meter, I’m 30W lower indoors, regardless of temperature, intensity, position. It’s very consistent. And feels very inertia-related (old CycleOps Magneto).
My TR FTP is set for indoor wattages, and my TrainingPeaks FTP is simply always 30W higher. When I upload TR workouts to TP, I copy over the TR TSS; when I ride outside, TP gives the correct TSS. Not to favor tracking on one vs the other but consolidating them has helped keep things straight.
Definitely feel like the respective intensities do their job even if the number is different. The indoor workload is SO much higher even with a lower power meter reading, but for sure some time outdoors each week helps ease any adjustment period.
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Strangely since I’ve been outside for the past 3-4 weeks, I can’t seem to push the same power as indoors. I’m not sure if it’s due to generally riding longer or just not having the flat consistent roads or steady longer climbs in my area.
I’m wondering if I just got good at pushing trainer watts!
Power is +30 - 35W [PowerTap] outdoors over indoors. FTP would naturally somewhat follow that rule.
On TreaningPeaks you can set different FTP for MTB and Cycling so i use MTB profile for indoor and Cycling for outdoor Rides. In TR I set my outside FTP and then I just reduce workout with percentage!
But I also wandering if I’m doing enough inside… Because I only ride indoors to train for outdoors…
I’m also affected by a high discrepancy between indoor and outdoor FTP. I use the same bike and the same PM. Regardless of the reasons, I would love to see an option to change the FTP for outdoor training, before pushing to the Garmin. Otherwise I painfully recreate the same workout in Garmin or Training Peaks before heading out. Or just don’t bother and go ride my bike 
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Id I remember outside workouts works fine if you have set outside FTP on your Garmin
I would appreciate an indoor and outdoor FTP setting feature. Even better would be make it customizable so you could also set it per bike when you know power meters have differences.
Reasons for my difference:
Power meter location at crank vs at trainer, drivetrain in between with maybe 3% loss
Different brand of power meter vs trainer
Cooling
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I hope this thread is still live. I got a power meter fairly recently and got a new FTP from a 12.5 mile tt. I’ve previously had difficulties with the ramp test giving me an FTP that was too high to make the following workouts achievable, so I was hoping that a longer effort would get me closer to my real FTP. However, doing my first indoor workout with the same power meter I had to dial the intensity down by 10% to be able to complete the workout. So what do I do? I’m not so keen on doing a ramp test. Should I just manually tweak the FTP in TR until workouts feel right?
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You might gather from a lot of the posts above you have the potential to push harder outside due to air cooling and momentum etc. But you may be restricted mentally by traffic etc. I finally overcome that latter barrier and pushed an outdoors FTP far higher than my indoors FTP.
I did 296w NP for 57minutes on Saturday on a TT and I probably could have went harder (it was 90% tempo HR and my legs were good for 134 miles on Sunday) but struggle to do 250w on the ramp test.
I’ve initially left things at 250w as it’s a rest week but when I am back on it I’ll manually up it to 260w and see how I get on, and might let it creep up further but I would injure my self if I jumped up 45w and probably couldn’t do it indoors anyway.
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I’m pretty sure that the FTP from the tt is considerably higher as my previous one because my power pedal has a -13 w offset against the turbo. I did 243 NP over 37 minutes and my previous ramp test with the turbo gave me 238. Impossible to compare really but I estimate +10w. I think I will just adjust the FTP manually. I’ve previously dug myself into a fatigue hole with interval targets that were too high and I don’t want to do that again. Regarding the temperature - I’d be interested to know if this is an issue for women as much as for men. I tend to be too cold rather than too hot and I find my indoor training temperature comfortable.
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What was your average power from the TT?
It was a flat course so quite close to the NP; the average was 292w.
I should have went harder for the last 1/4 I was all zone 6 based on an 250FTP. I forget the exact numbers but it was something like 338w for the last 5mins. The first 3 legs had been circa 26mph and the last leg 27.6 mph 
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