FTP Builder and ERG mode

Can someone help me with this. I started the 6-weeks FTP Builder. I’m in the 1st week.

Trainer: Saris M2
Bike: Bulls Harrier, Shimano 105 triple (50/ 39/ 30), cassette 12-25
Workout plan: 6 week FTP Builder
Workout: Strength, week 1

The workout looks like this:"

My gearing is set at 39/ 17 assuming that in ERG mode you ride a certain wattage regardless of your cadence.

How does it feel: Riding 90 watts is only possible with a cadence around 60rpm a higher cadence will result in higher wattage. the 125 - 155 interval is doable with a cadence of around 95. The 280W intervalls can only be made with a cadence around 120. This feels very awkward and I’m not sure if I’m doing wrong.

Is ERG mode actually working (or not) and is this something related to the trainer or Zwift?

Alex, I don’t know if it’s a trainer problem or not, but certainly ERG mode is not working. It doesn’t matter what gear you are in or how fast you pedal, when ERG mode is working the watts will be controlled automatically. Is the controllable function of the trainer working normally, as in, do you need to change gear to get up the hills? And ERG is definitely turned on? Obvious questions I know, but sometimes settings can be changed between rides.

Hi Neil,

Thanks for the reply. I don’t have to change gears while climbing, and yes ERG mode is on. When I use the Saris utility app ERG mode is working fine. The app has a 25W ERG test option so imo it is not the trainer.

Another thing I’ve read was the fact that maybe my FTP is too low in the settings. The training effort throughout the workoutplan doesn’t feel that hard.

My M2 is being delivered soon so quite interested to know if it will work correctly on the ERG mode. If mine does the same I will let you know

Hi Alex,

All trainers has a range in where they can operate in ERG more. Running in 39/17 may be a bit low. Try 50/17 that will have your wheel spin at higher speed thus the trainer can apply more resistance at lower RPM.

There will be certain intervals in ERG where you still have to change gears.

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I was thinking the same thing however it seems like it is not working across the full range of power levels, 90W, 125-155W, and 280W. And that it seems like the power is dependent on cadence. Makes me think that ERG is just not working quite right. It must be working though to some extent if you can make 280W in such a small gear even if it is at 120rpm.