Elite Direto wheel circumference nightmare

Hi something that has been doing my head in for a while and despite checking out the Elite site and scouring the internet I can’t find a straight answer. Ok, firstly, why do we need to set a circumference on a direct drive trainer in the first place? then Elite say that if you are using a 3rd party app then the circumference (they state 2070) should be /12 and you should input 173 as the figure?? you could have a mountain bike on the trainer so does that matter. So how does that relate to real world wheel sizes i;e 700c x 25 = 2105 and 700c x 23 =2095.etc… Well Wahoo is a third party app and I use virtual speed so does that mean that any of the Elite settings are a waste of time and if I chose to use the “real world” speed should I use 2070/12 or the actual wheel/tyre circumference divided by 12. Can someone just put this in Plain English for me please? many thanks

A direct drive trainer can only count revolutions. To convert to distance, this must be multiplied by some circumference. Since there is no actual wheel, you can input whatever you want, but you might want to use the circumference of your real world wheel circumference.

For the divide by 12, I assume that this is related to the internal drive ratio of the trainer which is reporting revolutions of a component/sensor that is 12x as fast as the cassette. This is likely accounted for in the Direto app but needs the /12 correction for other apps.

I use Virtual speed, which is calculated in the SYSTM using power, your weight and a bunch of other factors, none of which rely on speed/revs/circumeference from the trainer. Here’s a more detailed description. https://support.wahoofitness.com/hc/en-us/articles/4405896793490-Understanding-Virtual-Speed-in-the-SYSTM-app

Finally, riding a trainer, speed and distance is zero. All training/workouts/performance assessments are based on intensities and durations including power, HR, cadence. Any speeds or distances are fabricated and provided because many riders like to think in these terms.


Many thanks for the detailed explanation. Cheers