Gear, cadence, terrain, and speed

Long time Zwifter, coming back after a pause (I hope) and I’m noticing something I had not noticed earlier. Maybe this is old hat, or maybe new hat, or maybe it’s some glitch on my end -

When pedaling at the same cadence in the same gear, I expect the bike to move at the same speed, regardless of terrain (assuming no acceleration due to coasting down hill). Obviously when the road tips up, more power will be needed to maintain the same cadence (and speed, assuming no gear change). But! Zwift does not seem to work that way for me, even at 100% trainer difficulty.

Pedaling in the same gear, same cadence, when starting a climb, the power requirement does go up, but speed goes down! On a gentle downhill, the opposite occurs, going faster at the same gear/cadence (and assuming no “coasting” is happening).

The behavior seems to be “as if” the trainer difficulty is actually set to something less than 100%.

Note that one implication of this is that to maintain a constant speed and cadence on a climb, you’ll need to shift to a Higher gear. In effect there is a downshift being supplied by Zwift and you’ll need to shift up to compensate.

I can see a few possibilities here. Can anyone say which of these, or perhaps something else, applies?

  1. Things are working as designed, and in effect even 100 trainer difficulty does not match the resistance that would come from the same grade changes outdoors. In this scenario, constant gear and cadence do not produce constant speed.

1a. Perhaps this is a change put in place some time over the past few years, which could explain my not having noticed it before now?

  1. Something wrong with my setup (kickr bike, windows) that is producing less than 100 trainer difficulty when set to 100.

  2. Something unintended with Zwift that constant gear/cadence does not result in constant speed over different terrain?

Come to think of it… In the past I’ve used a lot of ERG mode, or equivalent, setting power level externally. So maybe this is not a new phenomenon?

In that case, should we be lobbying for something closer to a true 1-1-1 gear-cadence-speed option regardless of terrain?

Thoughts/suggestions please!

Riding alone, small group, big group? Pack dynamics may have changed since you were in game

Good question. Riding solo!

The pack dynamics changes should have no effect on solo riding. The question is whether the bike is measuring the same power as before. If you have historical data such as in Strava or TrainingPeaks or Garmin Connect that might help you understand if there is a difference. You might also want to talk to Wahoo support to see if they recommend doing a factory spindown.

I will give this a try!

However, if there is a bike problem I’m not sure that would account for the way Zwift seems to be effectively and consistently changing gear with changing grade.


Would be interested to know if others see this, or, alternatively, if a constant gear and cadence results in constant speed regardless of grade?

… My assumption was that 100 trainer difficulty should work that way, but for me it is not at this point.

… also, it appears that the kickr bike cannot run a spindown/calibration

What’s the firmware of kickr bike?

I use one and don’t get these issues. On ADZ a 14% gradient feels like it should and I have to change gears.

In Wahoo app you can quickly tap multiple times on the bike icon to access other firmware versions.

Latest firmware, 1.27.0

The effect is subtle, maybe only noticable on more gentle grades where you can push the same gear at the same cadence, and observe that you (well, I) lose speed.

A steeper longer climb is, typically, going to require a downshift, so the resulting speed loss is expected.

Still scratching my head on this one…

Might also be necessary to ride at a slower pace to observe this. If you’re pushing hard on the flat, maintaining the same gear and cadence up a hill could be impossible!

Isn’t that completely normal? Generally, we go slower uphill than on flat even if we’re putting out more power. And I can go a lot faster even on shallow downhills than on flats, sometimes even with less power downhill.
Of course, there’s a point where you could put out enough power on climbs to make yourself go the same speed as though it was flat (much less resistance). But unless the climb is less than a few %, that’s really hard to do.

IRL in the same gear and at the same cadence, we should be going the same speed. Of course, when ascending, more power will be required in order to maintain that speed. There is obviously a slight increase in distance when ascending (think triangles) but it shouldn’t be so large as to be noticeable I don’t think.

don’t think this is true, distance follows the gradient it isn’t just horizontal distance.

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More power and lower speed while climbing is normal! However, if the gear and cadence are constant, power should go up and speed remain constant on a climb (however gentle it needs to be to maintain the same cadence).

Zwift does not seem to work as above, to my surprise.

I wonder if others see this (on deliberate testing)?

I would have expected 100% trainer difficulty to match real bikes in this way. If it doesn’t, should it? Or do we need some sort of fix or option to match this behavior?

For my part I’d like to be able to hold speed up a small climb without having to shift to a higher gear, or pedal faster :).

Zwift speed is purely as a result of power, the game does not know if you have changed gear or not and it doesn’t take cadence in to account.
So it seems like the formula to work out speed at given gradients is a bit off.
You also have to remember zwift only changes resistance for gradient and no other forces that you would experience when cycling in real life. Hence why you slow down when cycling on gravel yet you feel no difference than cycling on tarmac through the trainer.

Good point about Zwift only working based on power.

Maybe that means that the controller resistance being applied isn’t high enough to maintain speed on small climbs at constant gear/cadence?

IF that is all true then it seems like raising trainer difficulty would be a good thing?

Hey Zwift Support!

Any odds of taking this on? Make a higher level of trainer difficulty available? It seems it would make for more realistic road feel!

I don’t think it will be any more accurate, just differently wrong.
Zwift only changes resistance based on one variable - gradient. There are many other factors at play, gradient will affect riders of differing weights differently, the slowing in speed will reduce the air resistance, this will affect larger riders more than smaller riders.

Ah. OK. I didn’t think Zwift was that sophisticated :wink:

Maybe so, hence the variable trainer difficulty setting I suppose. Seems like it needs an option to go to 110 or 120 or more, or similar!