KICKR Snap resistance control

raymond82

Hello there,

Since two months I have a KICKR snap but I'm quite unhappy with the way it regulates the resistance from an erg workout. Mainly with an increase in power the KICKR overshoots and with a decrease it undershoots by quite a lot. Here's an example of what was supposed to be a 2 minute under at 254 watts and 1 minute over at 304 watts (x3) using Hurts Ergo on my iPhone and bluetooth.



The fluctuations are quite big, this makes the workout quite a bit harder, that may not be too bad but I was wondering if this is normal and if there's anyone out here who knows how to make this work better. I've tried also Rouvy, both through bluetooth and with the power meter attached through Ant but the issue is the same. Any advice?

Many thanks!

nicklong

This is due to the flywheel effect - try riding in a lower gear (e.g. 34-23) to reduce the inertia.

When the flywheel is spinning fast, the electric brake seems to have to wait a few seconds for the speed to drop before it can regulate the resistance when the power target drops significantly. When the power target increases significantly, the ERG is quickly recalibrating to the new torque / power you apply and is then adjusting the resistance accordingly, but it takes a few seconds of heavy pedalling to adjust.

Basically, the Kickr is playing a constant game of trial and error, adjusting resistance and THEN seeing what power is measured, over and over.

raymond82

nicklong wrote:

This is due to the flywheel effect - try riding in a lower gear (e.g. 34-23) to reduce the inertia.

When the flywheel is spinning fast, the electric brake seems to have to wait a few seconds for the speed to drop before it can regulate the resistance when the power target drops significantly. When the power target increases significantly, the ERG is quickly recalibrating to the new torque / power you apply and is then adjusting the resistance accordingly, but it takes a few seconds of heavy pedalling to adjust.

Basically, the Kickr is playing a constant game of trial and error, adjusting resistance and THEN seeing what power is measured, over and over.

Thanks, I'm gonna try using a lower gear! I forgot to mention that I was already using quite a low gear (34x15 I think) but I will go a bit lower still. I also had the feeling that cadence had an effect, if I would drop the cadence too much with the increase in power the problem seemed to be even bigger.

Would the tire/flywheel connection also be of importance? For instance more tire pressure or tightening the knob more, maybe that's worth giving a try too now that I think of it.