Speedometer/odometer accuracy

[DickB]

I've found that the speedometer and odometer accuracy can be improved by changing the tire size from 26 to 28 on the controller display. 28" is closer to the actual size of the fat tires.  To change, power on the display, press and hold both up and down arrow keys, then use the up arrow key to set 28". My speedometer and odometer are now near identical to GPS.

[mckyj57]

I recently started using the app MapMyWalk, and it appears that the odometer logs about 7% less distance than actual. I will try 28" and see if it makes it closer.

[DickB]

A litttle arithmatic: (28-26)/26 = 7%!

[mckyj57]

I've been using 28" for 170 miles now, and it appears to be spot on.

[TravelforPictures]

This is great to know! I wonder why Rad doesn't correct it.

[James Glidewell]

I finally looked at the setup screen on my RR5 - it came set for 28". I don't know if they manually configure them at the factory, if so, the 26" might simply be a "typo" during factory setup.

[mckyj57]

28" is the correct setting, the one closest to actual. If you set it to 26", you'll register 7% less mileage than you actually travel.

It was set to 26" by the guy who built the bike, and that was wrong.  When I got to a thousand miles I figured out why Google Maps and my odometer were always in disagreement, and set it to 28". Now it's within 1%.

[JimInPT]

Doesn't increasing the reported tire diameter lower the actual motor-assist maximum speed?  A larger diameter will cause the controller to think you're moving faster for a given RPM.  Conversely, inputting a lower diameter will make it want to spin the wheel faster to achieve a given speed.

[James Glidewell]

I am pretty sure the default as shipped by the factory is 28" - otherwise it would not enforce the 20MPH limit as required for a US Class 2 ebike. Somebody screwed up when setting up the OP's bike and set it to rim diameter rather than tire diameter.

And yes, if you set the wheels to a smaller size, you will get a higher assist limit. But your odometer and speedometer will be inaccurate. And, if you care about such things, your bike will no longer actually be a Class 2 ebike, which means it can't be used legally on many mixed use-trails.