Kickr core - huge difference in watts between just 2 gears - is this normal?

Hi all

Took delivery of my kickr core today having previously owned a tacx flux s which packed up on me. Using the kickr today for my first ride I am unsure about the huge changes in power when changing gears.

I can’t remember the tacx being like this but there’s a huge diff in power between gears. So, big ring at the front, going along in 3rd hardest ring at back if I click up to 4th ring at the back there’s a drop off of about 100 watts and then it creeps up by about 30 watts or so over 10 seconds. Similarly, if I move from the 4th ring at back down to the 3rd ring at the back it jumps up about 100 watts then drops down 30 watts or so over 10 seconds.

Does this sound right? When riding on the flat if I’m in the 3rd biggest ring at the back I’ll push out approx 200 watts however if I moved into the 4th biggest ring at the back it’ll drop to about 105 watts then settle at 130 watts. This seems a huge drop to me between just 1 gear selection.

I’ve done the spin down etc. Did it a few times after test rides on zwift.

Thanks all

Are you using the identical brand / model / gear range cassette that was on the Tacx trainer?

If the number of teeth on the 3rd hardest cog & 4th hardest cog on the cassette isn’t identical as the cassette on your Kickr, that jump is going to feel different.


Hi shuji

It’s the same cassette I removed from the tacx so teeth are the same etc.


@shooj I’ve just done a 1 hour free ride again. The only thing bugging me is the resistance on the flat. On the hills it’s fine and I change gears accordingly. On the flat, if I’m in 3rd biggest cog on back it’s an effort but I can hold 180-210 watts fine. Soon as I click to the 4th biggest cog, so 1 gear easier, the resistance is wayyyy less. Like 100 watts difference

what is your cadence, RPM?

That’s with a cadence in the range of 82-88

I’m guessing that it has to do with the fly wheel speed. As you are in the harder gear and the fly wheel spins up gaining speed and momentum, when you drop to an easier gear it will take some time for the fly wheel to slow down a bit before you can feel the resistance again. Hence the large drop in watts and then a bit more power as the fly wheel slows down. This is probably what you are experiencing, does that make sense?

I sometimes get something similar to this but never 100 watts, usually 30 to 40 or something - i find it usually gets better once the trainer warms up a bit. It can be a bit annoying as one gear tends to be a bit too easy and the other a bit harder than I’d like.

that is using a tacx flux and also an elite zumo