A few thoughts on the STAC Zero Halcyon

Hey everyone,
I was lucky enough to win a new Halcyon trainer and have been putting it through a variety of workouts to test its functionality and compare it to my kicker.

  1. It really is SILENT! My fan and singing are the only things that my wife–bless her heart–can hear now.

  2. It is much easier to set up than the gen 1 and the auto calibration of the magnetic arms is great. Be sure to get the wheel centered though! You can do this through their app and initial set up.

  3. if you have a power meter already on your bike (I have the Quarq and the Powertap P1 pedals) be sure to calibrate the trainer to that by seeing the average difference between the two meters and then going through their app settings. Erg mode is pretty bad with power match BUT when you calibrate the trainer to your power meter and then do erg mode, it works much better.

  4. Resistance mode right now is my favorite mode hands down but I am already biased here. I am still testing Erg out with the new calibration at higher intensities.

If you have any questions or want me to do any tests, let me know :slight_smile:

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I’ve got one too. Since my home office (where I put my trainer) is next to my daughter’s bedroom and I do most of my training while she’s asleep, I’m really happy with the silence.

I have done the same thing with power calibration, and like you I don’t bother with power match because I can trust the trainer’s reported power. Since you have to install the freewheel weights in your wheel, I’ve got a dedicated trainer wheel so I’m not constantly adding / removing the weights, and I set it up with a single speed cog:
Of course that necessitates using Erg mode, but as a triathlete I don’t do a lot of sprint work where that would make much difference.

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Great points!

I actually do not use the wheel weights because they did not add that much of a difference. I also like being able to just take the bike off and ride without swapping out wheels.

Which gears do you use for Erg mode. I’m on a 1x bike and running 42 x 12 and I’m less than impressed with the inertia (both sets of wheel weights are fitted) and “road feel” Maybe I’ve been spoilt by my KK Rock & Roll with the heavier flywheel. Would swapping my 42 for a 50 make any difference do you think?Also whats it like pairing your phone to the trainer using their app.? Again my experience is less than brilliant. Sometimes it works OK, other times I have to keep switching bluetooth on and off until it works.

I prefer the 53/17 or 53/19 gear for erg mode. I find that is the smoothest gearing combo while in erg mode. During resistance mode 60% is a good setting for a variety of cadences.

As far as the app, I connect it before each workout just to be sure the arms are the perfect distance apart from the wheel. As long as all other devices with TR or Rouvy or some sort of bluetooth connectivity are not operating then I am fine connecting.

It is certainly not the same as direct drive but compared to wheel on, it is so much better in my experience thus far.

I’m running 50 x 16, I think? I got a cheap wheel to be my trainer wheel (so I’m not installing / removing weights) and a single speed ‘cassette’ that has 16 teeth, I think. I dunno about ‘road feel,’ as long as I have enough inertia that I don’t feel peaks and troughs in resistance it doesn’t matter because I’m constantly pedaling anyway.

The STAC Zero app on my phone is terrible, and crashes a lot. I don’t have a lot of use for it, thankfully.

Their support sent me this link if it’s any help

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I have a couple questions about the Halcyon. I already have a Stac zero trainer that I share with my roommate so I know i have the right setup, I’m just trying to figure out which model. Also, I don’t have a powermeter.

  1. Can you run the Halcyon in a setting besides ERG / SIM b(setting the magnets to a steady resistance)? I don’t always want to run ERG.

  2. Have you tried using it just based on their power match? All of the reviews I can find online are people using their own power meters so although i realize their powermatch isn’t accurate, I am trying to figure out if anyone has ran it just using their powermatch.

  3. Do you like it enough compared to your other trainer that you would recommend someone buy it? I have never used a trainer besides Stac.

But the trainer skewer is so ugly! I won’t be caught dead with that on my bike outside.

Great questions. Hopefully these help:

  1. I use the Halcyon both in Erg and resistance mode without any issue. Like the erg mode where it simulates a hill up to a certain percentage, you also run into that with resistance mode but that is only on one end of the extreme and I have only hit it once, after which I just changed my gearing to make it harder.
  2. What I did is use my P1 pedals to calibrate the built-in power meter, which you can do through the STAC app, and then put my regular pedals back on. TrainerRoad now only talks to the trainer and uses the power from that.
  3. That was is tricky. I like it enough to keep and use it when riding my road bike which is about 2-3 of my 7 rides a week. I have a kickr, which my TT bike is parked on for the winter, and do like the direct drive control of it. On the other hand, it is heavy, bulky, and large. If I lived in an apartment or traveled a lot, I would use the Halcyon exclusively and sell my kickr because of the noise and space it takes up. The resistance is “great” but not the same as direct drive, which I prefer.

I hope all that helps. :slight_smile:


Nothing really to add to @tribuddha post except I’ve been trying to align the power readings against my single sided Stages PM and it’s proving a challenge. I get it correct for one workout and then it’s out for the next. I suspect it might be something to with some varying leg imbalances I may have at different cadences/power outputs. I only use it in Erg mode sometimes letting the trainer control the power and other times using Powermatch with my Stages. In both cases it’s really good.

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I have what is probably the ideal setup for the Halcyon, my power meter is a PowerTap hub. Right out of the box they were quite close to each other, but over the course of a couple of weeks I tweaked the factor in the control app until my hub and my STAC Halcyon read within a watt of each other. Then I went another week where I was watching the power reported by my hub on my Garmin, but TrainerRoad worked entirely off the STAC.

After that I switched to a dedicated trainer wheel (I find installing / removing the weights fiddly, so I’d rather swap wheels than fiddle with the weights), using only the STAC for power. I dunno what reviews are saying their power reports aren’t accurate; as far as I know most smart trainers estimate power based on a spin-down calibration, and the STAC has an actual strain gauge in that block of aluminum.

Yes measuring power at the rim of the wheel will be different (lower) than crank- or pedal-based power meters, but that’s not inaccuracy, that’s measuring different things (force before and after drivetrain losses). I’ll take a calibrated strain gauge over even the fanciest estimated power any day.

I’m no connoisseur of trainers; I’ve had a cheap CycleOps Mag+, the STAC Zero, and the STAC Halcyon. The STAC Halcyon is a little more finnicky than the Zero, but I went through a whole 12-week traditional base mid volume plan (6-9 hours per week) this winter on it and it held up great. I’ve traveled with it and loved that it folds flat, and can run on battery power.

However, even after buying it I sort of feel like smart trainers are nice… but only marginally better than a dumb trainer. The real game changer is having a real strain gauge based power meter; whether that’s on the trainer or on your bike, that is vastly more important than the trainer being smart.

My trusty Elite trainer is starting to groan in its old age. Looking to possibly replace with a Stac Zero. Is it a hassle to switch between two wheel sizes? I’d like to easily be able to put my 650b bike and 700c bike on without too many adjustments.

Should be a pretty easy adjustment as I believe it is only 2 hex bolts to slide the magnets up or down. There is a possibility that you won’t even have to move them.

Thank you!! I would have not realized why the power readings are different between the trainer and a power meter, but this finally makes a lot more sense. I decided to go ahead and buy the Halcyon. I will probably borrow a friends power meter to calibrate the power meter on the Halcyon and then use the Stac power reading.

My point was the Halcyon was plenty accurate out of the box. I wanted it to match my PowerTap exactly so that watts on the trainer equal watts outside, but if you don’t have a power meter outside… it is plenty accurate without fiddling with calibration.

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