Doing crazy speeds on the Stac Zero Halcyon. Any one experienced this?

hey all,

I have just gotten the Stac Zero Halcyon trainer. in this case your rear wheel is completely free in the air and your resistance is provided by magnets.

Stac recommend that you use your highest gear, which means that during todays low power (less than 140w average) session i was “travelling” on average 45kmh. This is clearly ridiculous.

I know speed/distance has less meaning on a turbo but i’d like to have a realistic idea of how far i’ve travelled come the end of the year!

Any ideas?

Yeah. I had very low speeds for a while; I updated the software recently and now, like you, I have crazy high speeds (all for the same effort, of course). No idea why or how to fix it, so i just ignore it!

This is super strange, and sounds like a bug on Stac’s end. I’d recommend reaching out to their Support to see what they say:

Where is your speed value coming from? My Halcyon always reports a very low speed, around 8-10kmh; I have guessed (but haven’t done the math to confirm) that they are calculating speed based on the circumference of the brake track, rather than making any guesses based on the possible circumference at the edge of the tire.

On the other hand, if you’re using another speed sensor, then wheel speed could be high or low depending on your gearing (completely independent of resistance). Further, without changing the gearing, your wheel speed will only vary based on your cadence - so you might see an almost constant, high speed, regardless of the power you’re generating.

can you use the Halcyon for wheel speed??

I connect TrainerRoad to my HRM, Wahoo RPM cadence sensor, and the Halcyon - so the speed data must be coming from the Halcyon. It’s just the numbers are funnier than trainer “speed” normally is. :slight_smile:

matthew.weigel is right - the only speed reading that the Halcyon records is the speed of the wheel at the brake rim, and that is only meaningful as part of the power calculation.

Here’s a good article from Trainerroad about the relevance of speed in indoor training.