Inaccurate Speed Reading?

FAQs & How-tos
1

How to calibrate your speed

if your speed is way off, then you either have the

  • wrong gear ratio (should be 1.0 aka direct drive)
  • wrong motor poles, must be 30 (14 is default, all onewheel motors including superflux and cannoncore and cheap chinese hub motors use 30)
  • wrong tire diameter

All of these settings can be changed in VESC Tool, Motor Cfg, Additional Info

Note: none of these settings affect motor/board performance, only speed reporting accuracy, as well as efficiency reporting, distance reporting, etc

Speed seems fine but GPS reading is different

Measuring the tire diameter accurately can be tricky to do so my preferred method is to use GPS to calibrate.

GPS readings are not very reliable in all situations, but there’s one thing that GPS is really good for: measuring distance.

  • pick a straight flat road - the longer the better - or you can use a 400m track lap…
  • measure the distance using GPS (Float control tells you GPS distance or use other apps), or Google Earth
  • note the distance reported by the VESC, compare to the GPS distance
  • adjust your tire diameter proportionally

Repeat the run and verify that it is now closer. Now you can pick other straight roads and verify your calibration there to rule out some GPS anomalies…

How to get GPS distance in Float Control:

Hold the word “Trip” to get the trip summary view. Now hold the word “distance” to get distance details, including GPS distance

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How about a quick list of most common tires, rims and recommended values for most precise values?

E.g. we would create and mailtable a Wiki Post with a table:

Tire Size Hub Rim Savers Diameter Setting (mm)
Burris Treaded 7" TX11 11.5 x 7.0 - 6 Superflux MkII :x: 302.00
… … … … …
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I mean, the amount of variations when you get into hub and rim saver combinations and the number of tires out there gets to be pretty insane, and the hub and even rim savers can have enough of an impact that it’s probably not worth excluding either. And even then, you still have variation tire to tire regardless, which can sometimes be quite substantial depending on the manufacturer. A table wouldn’t be the worst idea, but it may be a bit misleading, since if someone truly wants an accurate reading, they should really just measure themselves.

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