# Wide variance is Speed Device numbers

I have done Torque Monster each of the last three Saturdays. 95% of the time when I ride on Systm the speed device defaults to Virtual Speed. Yesterday it defaulted to my Kicker Bike. I never noticed the huge variance between the two and may not have now except I just did the three rides and I was comparing numbers. Here is what a few of the numbers look like.

10/2/22: IF = 0.77, TSS = 40, Normalized Power = 171, Distance = 11.11 miles
10/9/22: IF = 0.88, TSS = 52, Normalized Power = 194, Distance = 11.43 miles
10/16/22: IF = 0.98, TSS = 62, Normalized Power = 213, Distance = 8.52 miles

Over just a 40 minute ride that is a huge variance. I know both measures are just an approximation and YMMV, but that really surprised me. I donât expect any of the speed or distance numbers to be just like I would get out on the road, especially given I never ride outside like I do in the structured workouts online. But I do look are improvements (or not) based on the relative differences between online rides. Clearly I canât compare the distance numbers unless I pick one Speed Device and donât vary from that.

So two questions.

1. Has anyone else seen this big of a variance between the two measurement tools?
2. Any sense of which might be the âcloser to realityâ tool?
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Virtual speed will always give you the most accurate and consistent approximation of distance (and speed).

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Glad to hear this Sir Glen. Otherwise, I am seriously regressing.

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IDK about a Kicker bike, but on smart trainers, âdistanceâ is calculated by counting wheel rotations assuming some tire circumference. Systm virtual speed uses power and some assumptions about ride physics to come up with a speed and distance. Personally, Iâd expect them to be way different, as theyâre really two different things, neither really corresponding to any actual physical distance.

And, FWIW, what matters in training, fitness, and riding is effort level and time. Speed and distance will depend on many other factors.

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Sir! You already know that speed and distance are relatively meaningless when it comes to SYSTM so I wouldnât worry about regressing. Also youâre a Knight GvA darn it so if you do regress, youâll do it SPECTACULARLY!!!

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Also, note that speed, and time in general, mean nothing on the SUF side of the valley. You might think youâve been at it for 5 minutes, but in reality it has been 15 seconds. Buckle up.

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Well acquainted with the Sufferlandrian time warp. I canât count the number of times I was sure I had ridden for a full minute, rode an extra 5 seconds just to be sure, only to see only 30 seconds had passed on my clock.

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Sorry. Yes I know you are Sir.