Downhill speed increases dramatically dispte Cadance and Gears not changing

I’m new to my Smart Bike and Zwift… wasn’t able to find a similar issue but suspect that’s because its user error!

When riding a route in Zwift (Not a Training session) I find that if I maintain the same cadence and don’t change gear my speed dramatically increases… why?

I have a possibly related observation when climbing a hill, I shift down a gear and only for a few seconds does it make a difference, but then the same resistance applies - even when I’m in my lowest possible gear… where naturally I should be putting in high cadence numbers but hardly moving! In this instance, it almost feels like I change down, but Zwift slowly just increases resistance because it wants me to struggle.

Any guidance or suggestions appreciated.

Without some specific examples of when/where you are seeing this it is a little hard to say if there is an issue, or what it might be. Heading down a hill, for example, your speed could increase, even if cadence and gears don’t change, due to a change in the steepness of the hill. Same goes for going uphill and slowing down. From what you are saying, it also sounds a bit like you might be in ERG mode, as opposed to SIM mode.

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Like Nigel said my first thought reading this is you were in a workout and the trainer was in ERG mode. During workouts/ERG mode Zwift ignores the gradient and tells your trainer to keep you at a redefined wattage. So if you downshifted in ERG your trainer would see lower power than it is being told to maintain so it ups the resistance to get your power back to where it should be.

When in ERG you shouldn’t shift, your trainer will provide the needed resistance. The only time to shift in ERG is basically the FTP test section of the long and short tests.

As a quick example… typically going 20mph with a cadence of 80… half way down the hill without changing gear (still producing about 80-100 watts) I’m travelling at 35mph. gradient wasn’t more than 5%. I make the assumption that as i am producing watts, and feeling Resistance the Sim isn’t simply free wheeling and accelerating purely due to it being a hill…

I was doing a route on Richmond, not Training - where i appreciate ERG would come into play.

Literally just sounds like you are going down the HILL? that makes you speed up just like in the real World due to physics

I absolutely agree… but there is still Wattage recorded, and that would imply I’m pushing the bike - when my gear and cadence would not account for nearly double speed.

Agree with others, sounds like ERG mode.

But picking up on your downhill speed comment, at a stretch, this could also be you not being used to Trainer Difficulty. Have you adjusted it at all? If not, move it to 100% and then see if you have the same experiences. 100% it should fairly well simulate gradients accurately. Downhill is a different beast as Zwift halves the gradient - throw in Trainer Difficulty adjustments and it can interesting - best to read this article to understand descending and Trainer Difficulty.


Unless you have a tacx neo 2t then the trainer flywheel does not speed up with the downhill, therfore you will always still feel like you are ‘pushing’ power but it won’t make a difference.

You can be doing 100kmph down alp du zwift and still apply 200 watts to the pedals. The watts won’t be effecting your speed the virtual descent is the thing that’s creating double the speed on screen

Thanks Adam - that’s good to know and would explain why I’m still pushing watts.

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