Chainring and Turbo Trainer

Question related to turbo trainer and a chainring. Apology if this has been asked before.

I’ve been training with the small chainring (semi compact 36) and let ERG do the rest I.e. handle the resistance, and no problems with that at all.

Thinking of training with the 52 chainring and 22 or 18 cassette and Wondering if my kickr core able to simulate power especially at the lower end of the resistance possible at the right cadence?


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If you use ERG mode, gearing doesn’t matter. You dictate your own cadence, so you can use 39x28 or 52x11 and cycle at the same RPM.

If you switch to slope mode or let the terrain grades dictate resistance, then you are able to use gearing.

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I have done this test many a time in the past and people may argue that the ERG mode will eliminate any “mechanical” changes one makes to the gearing. However, and this is my findings (I am going to use fictitious numbers just to provide some guidance). Now again, this is my findings and I am by no means an expert: I used to ride single speed and I then started using the ss on the trainer, the gear ratio was a 32T in the front with a 14T in the rear. I then started running out of resistance so I changed it to an 11T in the rear, same thing happened so I went with a 38T in the front.

Fast forward a couple of years where I’ve gone from the ss over to some gears (1x9) with the 38T in the front.

The resistance with this config works fine except on the high end of the spectrum. If I do a video with lots of sprints or let’s say the 5 sec sprint of the 4DP, I spin out, my trainer has a max resistance of 900W and I can only push around 600 before hitting a 150 cadence. So I then decided to go and increase the 38T to a 52T in the front and 10 in the back.
The result: My cadence is always lower than what the video requires, even if I go lighter in the back and I can push more watts on the sprints. So yes, ERG mode does provide resistance and it is suppose to make no difference when you fiddle with the mechanics of your gears but, the ERG mode has a band in which it operates (technical gurus please correct me if I am wrong) but my understanding is that if you increase the resistance of the gears enough then you can essentially override the ERG function and get more suffering for your effort


Exactly the response I was expecting. I ‘feel’ the ERG has that operating band though theoretically it should be able to power match regardless of the mechs.

In fact I have actually tried a few workouts on 54T x 22/18T (5th or 6th) I could sense that the kickr is struggling to lower down the power to match, say at recovery watts. Of course I could simply do it by dropping cadence (I think) but you don’t want to do that do you?

But then I might be wrong! Maybe it was just my feelings?

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I agree with you 100%, that was my findings as well :grimacing:

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You get the same resistance for different gears but all resistance is not created equally. Shane Miller explains here…


Thanks for the video spot on! The comments on the videos were helpful too.

I’ve been ‘climbing’ all these while!

There’s no right answer to it but there are differences. For majority doing high watts block training seems easier on big gear.

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Well, I can’t argue with the likes of Shane :slight_smile: Still, I have spent countless hours and tens of thousands of kilometers on my smart trainers and ERG for me is gear independent.

I can chose a higher or lower RPM, which makes for good cadence drills, but that’s it. And for me, higher power levels can be easier doing high RPM too. It depends on the sort of day I’m having.

There may also be a difference depending on your smart trainer though. Or, it’s just a personal ‘feeling’…


At minimum, I would think that having a middle gear on the cassette to give your chain the straightest line would be the most efficient. If you’re constantly running the big ring and the smallest or largest gear on your cassette you also run a higher risk of dropping your chain and also losing some wattage due to drive train inefficiency because of your chain angle.

Having just got my Core a few weeks ago, I’ve been playing around with a different gear selection, as well, and I feel like it does matter. Even when I was on my old dumb trainer, doing 250w in my small ring as opposed to 250w in the big ring felt different, even when at fairly similar cadences. I think it may have to do with the gear ratio that you’re using, as well as all the technical stuff that Shane mentioned in his video.

If it “feels” different to you, there probably is a difference. So, pick the gear that feels right for you.


I had a really hard time adjusting to ERG mode. I’m new to virtual training and had done some trials of Zwift and Rouvy, which operate in “sim” mode, which adds resistance as you go up hills. Sim mode feels very natural and relies on you changing gears. ERG mode completely through me for a loop. I wish I would have found this post (and Shane’s video) before I started doing videos in ERG mode.

I do find that my Wahoo Kickr Snap works best in a higher gear. I have a triple chain ring and I usually run the training using my large chain ring. I find that using the smaller rings tend to make it feel more like climbing and also make it hard to adjust to sudden increases in ERG power. Conversely, I find that using the large ring makes it harder to adjust to sudden decreases in ERG power (during recovery periods).


I guess We share the same ‘feelings’. It’s just that the default gear that I spent most of time in when on the road is 54*18 and i can’t help but notice the different sets of muscles being used unlike during the indoor workouts (though at same watts, technically).

So this time around I’m going to train on big chainring to replicate that ‘feelings’ as close as to the road riding.


Exactly ! Same message, different context :ok_hand:t4:


Did the hunted today on 2*7. Felt the difference. More road-like :+1:


That’s true and I do that, either on the big or the small chain ring. Chain is usually wearing out quicker than the cassette, but I do use the other rings on the cassette to make it last longer.

That’s probably more due to your static position…