Maybe its in my head, but when I use a Wahoo cadence pod and Kickr for power, I feel that it is smoother than when I use my Powrlink pedals for power and cadence.

The reported values are for sure smoother because of how a Kickr in a certain setting reports power to Zwift. Versus "actually what is read at the crank/pedals" could be bobbing around.

I don't like the idea of slope mode because it forces you into a kind of set rpm for a set power. Outdoors the terrain changes and you may be putting out that same power a faster or slower cadence. In theory in erg you can intentionally vary it a bit within a workout if keeping it "smooth" without altering the power output much.

But, am getting a bit annoyed at this point. I recall the erg mode of an old old ass Cycleops spin bike with a Powertap meter on it with erg mode from an old basic head unit would seemingly control power steady better than this Kickr/Quarq combo does.

I do bet it has to do with Zwift listens to Quarq for power, hears Quarq, tells Kickr what to do. And that's thru bluetooth on a laptop versus a head unit to something. Maybe signal latency.

Last week 3x9 under over at same power was attrocious. This week the 3x12 version I could do. Difference being in erg I used the inner ring instead of outer. Then again could just be gains.

I did a further test. I paired just the Kickr to Zwift, and my Assiomas to my road bike Wahoo gps and the Quarq I've been using on the TT bike for Zwift workouts to my TT bike Garmin gps. I set up a zone 2 erg workout to just ride for a few minutes in my pijamas.

Whoa and behold, it does what you would think it all should do and they all mostly matched within 5w. If there was a difference it was what you would expect of the Assiomas or Quarq reading a hair more than the Kickr.

So, still. Cannot understand.....why would the Kickr alone feel easier for some of these workouts? Gotta be a micro control thing where Kickr alone I guess it keeps the resistance more the same as you pedal but with talking with a meter also in the mix the latency causes more power spikes and valleys.

Completely agree. But the algos to accomplish this might bother folks who settled into the lower end of the range and then effectively had to 'pay it back' in the latter half of an interval, rather than the kickr's approach which is to obsessively keep you on target, even when it means jacking around your resistance the whole time.

I'm sure there is a smarter way to do it, but I bet the reason they haven't comes down to software engineer and product team lead resources. To get it right would be expensive unless someone on salary took it on as a pet project outside of company time. It probably takes a pair of folks to do well.

I feel the same about cruise control when driving my RV by the way, and have had hundreds of hours thinking about how I'd make a slacker, more grade- and course-optimized cruise control for maximum time-savings and improved fuel efficiency. I'm sure similar thinking applies to the trainer power issue. I suspect that the edge cases with hilariously bad outcomes expand rapidly as you expand the "slackness" of the system.

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Dr. Alex Harrison | Founder & CEO | Sport Physiology & Performance PhD
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