Same Watts feel much harder in Zwift - Computrainer & Mac

(Milly De Mori) #1

Hi there

I’m new to Swift and have used it a couple of times already, I use a Computrainer & Mac (OS X 10.11.5).

In both rides, at roughly the same power value, i’m experiencing a  “harder than usual” resistance in the Zwift app (on a flat terrain) rather than in stand alone ERG mode on the Computrainer (not connected to a computer and using just the head unit).

For example @ 140watt on stand alone ErgMode Computrainer i’m able to keep a more agile cadence, around 85/90rpm, while in Zwift it feels really hard and my cadence drops at 60-70rpm.

If there’s a bit of an incline, like +0.5% the climb feels even harder & cadence drops further.
1% feels like i’m climbing at 10-12% in real road conditions. 
Very strange.

Computrainer is calibrated before starting Zwift at around 2.3 pounds… I usually keep the value between 2.00-2.30.

Has anyone experienced the same?
Any words of wisdom to have a more realistic resistance translation?

thank you



(JD Griffis) #2

Try adjusting the Trainer Difficulty setting to a lower value. Despite the unfortunate name, it is really best thought of as selecting a different cassette. Lowering the setting is like switching from an 11-23 to a 12-25 or 27 (at least that’s how I understand it, and the effect that I see). So, you rely more on cadence and cardio, vs raw power.

(Duane Gran [Vision]) #3

I have two computrainers and use them on Mac and Windows and I’ve never experienced this.  I second the suggestion to experiment with the difficulty setting.  In general I find about 30-40% to be the sweet spot, but even the default at 50% feels okay but the 100% setting is simply awful in terms of simulation value.

Another thought, is the chipset version of your CT perhaps a bit on the older side?  It shows on the display of the yellow brick when you power up the load generator.  Mine says something like 43.45.

(Milly De Mori) #4

Thanks JD & Duane for feedback.

Computrainer chip is like yours at 43.45.


I’m reading on this forum about trainer difficulty setting and how it simulates “road conditions”, and i’m getting confused on the shifting side of things.

I thought that by using a smart trainer, you didn’t have to shift gears when hitting climbs (or keeping a certain pace), because the software is already compensating and all you have to do is try to keep that particular watt output in the same gear… (just like when using the computraier stand-alone/software)
However i’m reading about people that are shifting and using their gears as you’d do on the road.

If this is the case, it does then make sense that climbs feel super hard even at 1%.

Could you pls clarify?

But then i wonder also if necessity of using the shift would apply to both training session AS WELL AS to joined rides?

many thanks!

(JD Griffis) #5

When you are doing normal rides or racing, you absolutely want to shift gears; just like you would in the real world. The smart trainer is adjusting resistance based on terrain; but it is not fixing/holding any particular wattage. you control your power output based on the gears you select and your cadence.

When you do a workout, the default setting is erg mode; and that is when you don’t need to shift gears. In erg mode, leave the gears alone and hold steady cadence - let Zwift and your trainer adjust to achieve desired power.

(Milly De Mori) #6

Thanks again JD for clarifying.

I think the issue i wrote about in my first post was relative to “workout mode” and not a ride, but i’ll try again and see what happens.

I tried doing an FTP test and left it half way because it was way too hard to pedal at my presumed ftp, or actually i could sustain it but with a very low cadence. 

But i want to tweak settings and see what happens. I’ll try adjusting the trainer difficulty and report back. 

Thanks again!



(Ray Ruyack) #7

Let us know what happens.  Workout mode does feel slightly different but not much.  In that mode (ergometer mode essentially) you do need to keep your rpm’s up - better than 85 or so.  Dropping below that it gets very difficult to turn the cranks.