Big vs Small Chainring - Same Power (ERG Mode Gearing)

I agree with you. It’s not easy to make conclusions of this, that’s why I will try to experience by myself to find the best solution for further customers.

Regarding the testing protocol, travel has probably a (negative) impact, but on the other side :

  • I always ask them to do nothing on Friday morning (arrival day) and very light on Thursday to be fresh on Saturday morning for the test. I wish I could take two days off before a test lol
  • Travelling to Mallorca is pretty fast. Most of the time, people fly 1 up to 2 hours, not more
  • Performing a FTP with people around you increases motivation I think.

My personal test of this morning is already convincing me (went from 333 to 347 without pushing too much today).

For what its worth, my indoor and outdoor FTP is the same when using big ring on wheel-off Kickr 2017.

Not the best example… yesterday I did a 6-min climb up 10% grade in 36x32 gearing (needed 34x34!!!). Ridden at threshold by feel and I left ClimbPro on Garmin 530 display. For reference LTHR is somewhere between 158-161bpm and max is 175.

Definitely could have kept going for 20-40 minutes, not saying that is a great example as its only 6 minutes but it is consistent with previous long climbs at threshold.

On both flat road and climbs, my indoor and outdoor FTP seem very consistent. TR PowerMatch inside using Stages LR power and Kicks 2017 wheel-off trainer. Right now on trainer I’m using 53x19 or something.

I’m definitely going to keep watching this thread and will eventually test this a little more carefully myself as well, because I still haven’t done a perfectly controlled test either.

The funny thing is my only real prior motivation for one vs. the other was that the big ring and higher flywheel speed gives me a more realistic “mileage” estimate consistent with my outdoor riding - while the smaller flywheel is quieter. But now I’m going to explore this a bit more carefully on the power.

By the way, I’m making my first trip to Mallorca in January - flying to France for work via Barcelona, and when I saw flights to Mallorca for $15, figured it was a no-brainer to do a week layover. Looking forward to burying myself in cycling mecca!

:+1:t3: So 3 of 4 match (climbing, flats, big ring). Now you just need to test little ring inside :grin:

Little ring on trainer has been mixed as stated earlier in thread. Right now I’d bet ramp test would give lower FTP (ramp is max aerobic power aka MAP test).

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I have been struggling to try to understand the power differences I get between my Stages L/R power cranks and my 2017 Wahoo Kickr (see Power mismatch -- Wahoo Kickr vs Stages Cranks). In a nutshell, I am seeing a greater than 10% difference (with Kickr being higher) between the two power levels when doing TrainerRoad intervals in ERG mode. When just riding on Zwift in SIM mode, the power levels seem to be much closer together.

Well, I had been doing all my TrainerRoad workouts in the big ring (53-14 or -15). So, after reading through this thread, I decided to do today’s workout (Antelope) in the small ring (39-17 or -19). Well, in the small ring, the Kickr and Stages power levels were very close to the same! I did the last interval in the big ring, and the big difference in power levels (with Kickr being higher) returned.

Subjectively in that last interval where the Kickr power level was higher, I felt like I was actually putting out that power level. But there were also times when I felt like there was a bit of almost “coasting” going on when I overshot the target power and the Kickr was adjusting.

I haven’t done an FTP test in the small ring, but I have done the tests with Kickr power versus Stages power in the big ring. With the Kickr I was at 237; with the Stages, I could only manage 202 (though I was not in as good a shape, but should not have been that different!).


I did the exact same experiment one month ago during a Ramp Test on small ring. Have used DC RAINMAKER analyze tool to compare data of Powertap pedals, Stages (Left only) and the KICKR 2016.

Don’t take care of Stages data. There are higher than the Powertap for a simple reason : I put more more on the left leg, except at high intensities. But if you compare Powertap (ELEMNT BOLT with KICKR (Ramp, you can see that the KICKR drift at the end a lot. Don’t know if it happens on big ring as well however but maybe the KICKR take into consideration the fact that it retains pedalstroke or something on small ring ?!?

After some time adjusting going from 39/19 to 53/15, my cadence has dropped, also feel i use my leggs more (got a few days of stiffness). But my FTP seems the same.
I use Tacx NEO
I do feel that higher gear is more right for me. Outdoors i have about same watts on flats as in climbs (I think).

To add to your statement, can you tell us if you’re typically better at climbing or riding on the flat relative to others you size and power?

I just did set my venge up on my neo 2 to be able to compare my outdoor vs indoor watts and it turns out the s-works power cranks are consistently reading 10-12 watts higher on the small ring and 18-20 watts on the big ring.

I suppose it’s to be expected for the trainer measure a lower wattage. Did you guys experience something similar?

Varied power measurement from low flywheel to high flywheel speed is documented on a couple of trainers. The Neo (not sure the specific models proven) and H3 for sure. I can link to videos showing the testing and data (from Tariq Ali and Shane Miller from what I remember).

So, it’s a known issue that faster flywheel speed leads to divergence from “real” power meters on at least some trainers (and pretty likely more).

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Thank you for the quick answer. I watched the video but was suprised still the difference is this big. 20 Watt is quite significant.

So it’s been reported by a few here that training exclusively in the big ring negatively affected their real world climbing ability, but what about the opposite? What if I’m training specifically for triathlons with pancake flat bike portions, any negatives to training exclusively in the small ring indoors?


N=1 for me:

  • I trained 75% or more in the 34x17 combo the last 3 seasons on TR.
  • I do add plenty of standing breaks at 50x17 for comfort and to change muscle loading.
  • I also using 50x17 (and similar ratios) for “low cadence / high force” work to replicate climbing.

And despite that “low inertia” focus, I have had increasingly good results on the bike legs of my duathlon events. I also had decent results in my road events (other than some bad strategy decisions in one) in the same time periods.

I am experimenting a bit more this winter (spurred from these discussions) and trying more high flywheel speed training. I can’t make any claims other than I can “tell a difference” in the feel of the differences. I don’t know if there is any “negative” from the low speed training for high speed users. Pretty impossible to know without more good data or personal experience, unfortunately.

I can’t say that I feel I am missing anything specifically, but I am experimenting to see if I notice any differences rolling into this season.

Edit to add: I am 5’-10" and 145 lbs on a “loaded” day (about 3.9 w/kg), so that likely impacts my experience inside and outside.


This topic seems to be very personal and individual. Personally I think you should experiment and go with what feels right.

FWIW out the door for 6+ months of the year it is pancake flat but brutal headwinds, my favorite training route and weekly Wed night worlds feel like a 60 minute climb in the nearby mountains. And on Wed night when fitness is high I usually put out more power on the tailwind return. I’ve had very good success using large chainring on the trainer, for both these flat/windy rides and long climbs (1-3 hours) in the Sierra mountains.

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I exclusively train on small ring (36) on TR, mid-cassette on the rear. Only to limit noise and vibration (Wahoo Kickr). I am a all-rounder rider, like to climb, like to put big watts on the flat as well. Feel VERY comfortable on steady pace efforts outdoor at 85/90% FTP, including on flat.

Don’t know if it is related to training on small ring indoor, but I like low cadence a lot outdoor. I train around 90-95 indoor on TR, but most of the time around 70-75 outdoor, even on flat section. Feel like I try to find the same kind of resistance with big gearing on the road. If it’s ok to be above 90rpm for me on TR, I feel like I loose “control” on the road above 85rpm. Weird.

Regarding numbers, my outdoor FTP/abilities follow(s) the same curve as my indoor FTP, no matters the gradient, etc

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Yes, I noticed that.

Slightly different muscle utilization.

I would switch to the big ring. It’ll take a few sessions to get used to.

Yeah, it makes sense to train to your most relevant strengths

What I’ve noticed with the Wahoo Kickr and Vector 3 dual sided peddles.

10 min warm up then perform a spindown calibration, and calibrate the peddles.

Today I was doing taylor -1, so VO2 intervals with the peddles on the garmin, trainerroad on the kickr. The warm up and first 2 intervals (of the first set) are on the big ring, from there swapped to the small ring as the power was 10% down, target 330, actual 300ish. Dropping to the small ring actually made things worse initially.

What you do see from the data though is that as the trainer warms up the 2 power meters gradually come back into line, after 26 minutes riding time they’re both reading almost exactly equally. My surprise here is how long and how hard you have to work it before the trainer warms up. I’ve felt something was a bit out now for a while, looks like it’s solved.

Thursday is SS, so I’ll do some back to back with big and little chain ring there.

A lot of the data here relies on the assumption that trainers measure power in a consistent manner regardless of spindle speed - a pretty large leap of faith. I have a lot more faith in the tests that include an independent power meter than those which don’t.