One Trainer, Two Cyclists

Hello Zwifters !

Due to COVID-19, my girlfriend has started doing some indoor workouts on Zwift using my Kickr Snap, instead of going to her spin classes.

She loves it, but we suspect the power numbers to be inaccurate, due to the fact that we use two different bikes on the same trainer:

  • my BMC has an 11-speed Shimano 105 groupset and is equipped with an Elite Coperton trainer tire;
  • her Lapierre has a 10-speed Tiagra groupset and is equipped with regular road tires;
  • we both inflate our rear tire at the recommended tire pressure of 110 PSI;
  • I weigh 12 kg more than her;
  • one of us performs a calibration spindown once a week;
  • between us, the trainer is used almost every day.

Do we need to calibrate the trainer every time we switch our bikes ? Is a factory spindown required every time we switch ? If so, is it even possible to share a wheel-on trainer between two different cyclists ?

Thanks in advance for your recommendations !

I calibrate each time I swap bikes; it’s a pain but seems to be the only way to get consistent data.

I was afraid this would be the only solution (besides buying a second trainer) !

It is indeed a bit of a pain, especially since I mostly do workouts in ERG mode and they usually don’t incorporate a 10-minute warm-up. Oh well, I guess I just have to get used to it !

I was also thinking that I could use the “Control with ANT+ power meter” in the Wahoo App, which would get rid of the necessity to do a spindown, but apparently Android phones don’t have that option !