Too low Speed in Tacx Desktop App - Calibration looks difficult - constantly overrun by opponents. 26" as a problem?

I switched from the Flow to the Vortex Smart 2180.
I use an old Cannondale 26" MTB with a Schwalbe training tyre with 1.995mm circumference.
When calibrating, I have to go all the way towards loose with the screw. And I end up just to the left of "too tight". Nevertheless, the tyre slips on every climb.
When riding in the desktop app, I see relatively similar watts compared to my power meter on the real bike but it feels heavier. I ride at about 2 - 2.5 watts per kg of body weight. However, I am constantly and easily overtaken by other bikers for whom values in the range of 1.5 - 2 W/kg are displayed. My speed in the app is also about 25-30% lower than what I achieve in reality with the same gear ratio.

Is it possible that the Vortex cannot work with a wheel circumference of less than 2,000mm?
What else can I do to get a fair performance displayed?

0 jaimegu over 3 years ago

Several questions here and I'm still not sure if I can answer one question. Since no one has replied, let's give it a shot:

CALIBRATION

What's the tire pressure you are using? I pump closer to the max allowed by the tyre and rim. Then you are supposed to warmup for 10-15 minutes before performing the calibration.
If you don't have a reference powermeter, just leaving within the accepted range is close enough (as you confirmed by the on-screen watts).

Tyre slippage is more of a function of the cadence, the higher the cadence the less slippage.

FAIRNESS

Did you enter your weight in the User profile in Tacx Desktop? Not sure what happens with the integration with Garmin Connect, but check both profiles to see if the weight is correct.
Still in the same User profile in Tacx Desktop App: There is a section about the bike. If you select road bike profile it will be lighter, have less rolling resistance, be more aero and larger wheel circumference (not sure what's the point) compared to the default MTB profile. You can create your own profile.
There are two parameters in settings/training that might affect your ride but I'm not sure if they affect fairness: Difficulty and Road feel Intensity. I have both at 100%

a 26x1.95 tyre has a wheel circumference of 2050mm...

I don't know what is your real bike, but "same gear" is not a fair comparison unless it's the same bike, same wheel, same maintenance and same conditions (weather, slope, draft). So start by checking the bike profile as mentioned above

0 5727596 over 3 years ago in reply to jaimegu

Many Thanks!

Calibration:
I resolved slipage via increasing tyre pressure to the maximum.

Fairness:
Problem came from using a MTB profile. After switching to Road Bike speed shown in Tacx Desktop App is nearly the same as in real now.
"Same gear" is based on a gear ratio calculator. This is purely maths based on numbers.
BTW: Circumference of my 26" training tyre is 1.995mm.

Problem solved