Erg Mode - Gearing Ratio

So did a workout on Zwift today and found the erg mode quiet difficult, so after a little bit of reading i see changing my gears was the wrong thing to do.

So looking for an idea of the ideal gear ratio for ergo mode?


if you have a smart trainer, the gear ratio shouldn’t matter. when zwift asks you to do 150 watts, the trainer will adjust difficulty so that you are putting out 150 watts regardless of gear ratio.

ERG is really nice - you can do workouts without worrying about gears or terrain. you just pedal and zwift adjusts everything for you.

of course, that defeats a lot of the realism that “just riding” adds in. i find it’s nice to go back and forth – one night i do a free ride, another night i do a workout. it keeps it interesting.

From my experience with ERG mode having your chain on the small chainring on the front and something like the 15 or 16th tooth sprocket on the back works best. The big chainring works but it makes the flywheel on the smart trainer spin faster resulting in more noise. I also find power accuracy better on the small chainring.

If you’re finding things tough going in ERG mode check that your FTP is set correctly. You could be just having a bad day or it’s a tough workout. You can lower the workout intensity with the bias button in the Zwift companion app.

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Thanks for replies.

My FTP is correct, well fairly close anyway.

My main issue was getting my cadence within range while hitting the power required. Over spinning(rarely) a lot under spinning/grinding

In general, ERG is pretty great - but it’s not without some issues. Each trainer is a little different re: how quickly they adapt to changes in your power targets between intervals (i.e. how rapidly they ramp up resistance and back it off) and how well (and quickly) it adapts to changes in cadence. It’s all related.

In time, you get used to your trainer’s little quirks and adapt accordingly. Things like briefly spinning up to a very high cadence just as you go from low to high Watt target because you know you’ll get dragged back down by 10 RPM (or whatever) as the resistance ramps up.

The toughest thing to wrap your head around at first, I think, is the idea that spinning faster (without shifting gears!) will make your life easier when you’re already suffering to sustain X RPM. That is, if you can muster the willpower to get your legs moving faster (X + 10 RPM) LONG ENOUGH for the ERG resistance to back off… you’ll feel some relief and be able to stay on top of it.

Also, FWIW, I agree with Nigel re: using the small ring w/ ERG. In addition to being quieter, small rings are also cheaper to replace when you wear them out! :wink:

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I think Shane Miller has a video on this on his youtube channel