Acceptable watts fluctuation for erg mode?

I’m interested to hear form folks how much their trainers wattage fluctuates when holding steady state intervals be it sweet spot/vo2 or whatever and what is an acceptable range for a trainer?

For reference I ride the new wattbike Atom and I’m aware of the erg mode issues it has and recent updates have improved things slightly but I’d like to know what I should really be expecting from it?

Eh: today I did bashful+2 and during the 1.30 vo2 intervals it would regularly go over and then back under the prescribed wattage by 20+watts…never really settling. My cadence was solid never changing from 98/99.
It does exactly the same on all efforts be it sweetspot or threshold and by similar numbers.
I’m sure I read DC rainmaker saying that he gives a tolerance of maybe 10 watts but never seems good trainers go out by more than 5?

Also whether these constant small (ish) jumps will make the workouts harder?

I have a Neo 2T and it keeps you in a really narrow range in Erg mode. If I have it in the little ring, it will keep power to within a few Watts all the time; in the big ring, it will take a few more seconds to pull you back to the target value if you change your cadence or if the target power changes substantially.

I know this isn’t what you want to hear … but before the latest UK lockdown I tried a Wattbike Atom ( the latest commercially oriented one) and couldn’t believe how bad it was - possibly because they haven’t updated the firmware? I found it constantly hunting above and below the target power by up to 20-30 Watts if I even fractionally changed my cadence. If it were mine, I’d have sent it back - it was mentally exhausting trying to pedal carefully enough that the trainer didn’t respond so harshly that you went way off target power.

Sounds about right, here is my Bashful +6 using power pedals and a Saris H3: - TrainerRoad

The little spikes are usually caused by your input, not the trainer adding resistance, unless you ease up and it has to add resistance to keep the interval average on target. In short, I wouldn’t sweat it, 20-30w is not a huge thing for that kind of effort, just don’t pay much mind to those numbers or you’ll just doubt yourself for no reason

I have a Wahoo Kickr Core 2019. Looks like mine during SS workouts fluctuates about 10w +/- mostly. If it goes a little higher/lower than 10w it’s usually because my cadence also changed a bit as well. Here’s a recent SS workout using Powermatch (Quarq PM):

I’ve had that happen both inside and outside. Here are some poorly controlled 1-min jobbers done outside last week:

Now that is some oscillation! #strugcity that day :exploding_head:

However it doesn’t usually happen when:

  • I’m actively working to pedal smoothly and in circles (vs ‘kicking’ over the top)
  • I don’t over-power the start of interval

Some examples of good intervals both inside and outside:

Kickr 2017 (wheel off) on Bashful -3 using PowerMatch with Stages crank power meter:

That was in Erg mode and big chainring which shows more realistic power deviations, as compared to outside.

Closeup of the first one (in 2nd set) with some statistical data:

Now I’m going to compare that inside 1-min interval to a similar interval done outside:

Absolutely no concerns on either inside or outside.

I get that different systems are going to have bigger or smaller wattage swings when in ERG. But I don’t even look at the power target when doing my intervals, never. I focus all of my attention on holding a sustainable cadence and - wait for it - SMOOTH pedalling. If you are a rider who drives every pedal stroke down with authority you are just naturally going to have a jumpy power line, regardless what trainer mode you are using.

Also, does it really matter?? You’re body is still working in the prescribed wattage zone/level. You’re still going to get faster even if you never learned to colour in between the lines :wink:

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