Indoor Power Variances


#1

Not sure what’s going on…
I use a Kinetic Road Machine and Vector 2s power meter. Always calibrate the same before each workout.

Example: Many workouts start with me hitting the correct power target for an interval at a reasonable 90rpm in a given gear, but then by the middle of the workout I have to spin 95+rpm in that same gear to hit the power target. When this happens I will often see the power numbers move 20 points above to 20 points below back and forth without me changing gear, rpm, or drag (dumb fluid trainer).

It doesn’t always happen, but when it does I end up blowing up and failing to finish.

Anyone have any ideas?


#2

Hey there!

I’m really sorry to hear that your Kinetic Road Machine isn’t as consistent as it should be. Have you considered reaching out to Kinetic to see if this is an issue they’ve seen before?

The Kinetics tend to be very consistent trainers, so it’s possible that you’re experiencing some kind of defect. If it were to experience some minor overheating, it should not be so severe that it ruins your workout, so I would recommend reaching out to their support.


#3

Could be the change in viscosity as the trainer warms up.

I can’t find it now, but I once ran across some guys who measured the temperature of the fins over a workout - I seem to remember it leveling off pretty quickly (inside 5 minutes).


#4

I have had similar experiences on my Tacx Vortex lately, both when using Power Match and using the trainer in resistance mode (effectively using it as a dumb trainer). I think it may be due to connectivity issues with my power meter. A TR support person has confirmed that there has been issues on some of my last workouts, but I am unsure to what extent. It would be great if we could see the connection data for our rides ourselves. That would make troubleshooting much easier. Would that be possible @Bryce?


#5

I have a similar set up to you but with the 3s power meter and a CycleOps Fluid2 trainer.

I notice that when the trainer is warm the resistance increases, ie my cadence drops for the same power output. Which is the opposite response that you see. I don’t see this as a problem, as its just a case of changing gear to get to the correct combination of cadence and power.

What I do not see is the short term fluctuation you report.
What is the frequency of the fluctuation of power?
If it is every second or so, I’d assume its an imbalance between left and right leg (your power meter only measures left pedal power and doubles it for the total power - ie aassumes equal leg power).
If the fluctuation is after a rest interval, i’d assume its the trainer cooling - and the resistance curve changing subtly with temperature.

I cannot see why the resistance in a dumb trainer like ours would change up and down when in “steady state”. I could understand it going in one direction or the other, but not fluctating. I think the answer is more likely the power meter than the trainer.


#6

Just a thought, but could it be you ratherthan the equipment? You say that when this happens you end up blowing and failing to finish. Could it be you’re fatigued and just struggling to hold the numbers?


#7

100% same experience when I used to have a Fluid2. It was just a matter of getting used to the trainer itself (and keeping a close eye on my 3s power meter numbers), then adjusting the gearing as needed.

At the end of a workout, I could fry on egg on that thing!