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I don't know much about this device but I am getting ready to push the button on one.
If you are only 1 mile out after 144 I would be impressed
If I am understanding your question correctly, given the "error" between your bike trip and tuner you have concerns about rpm.
Again, speculating, but I suspect that rpm will be more accurate as it will be measured directly. Speed and distance are then calculated from that (taking in to account gear etc) so any time you introduce calculations in to a system like that you are bound to introduce errors - even if only due to rounding of the raw data. I may be completely wrong of course.
Also, even if you have a less than 1% error, these are engines that are being tuned so I doubt they are going to be so sensitive as to have that error make a difference.
Would love to hear more about this device as it looks awesome
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