Actual speed restriction

[gunshot72]

I’ve noticed that when my Shimano e8000 display reads 25kmh and the assistance stops my GPS unit actually reads 20kmh. GPS is more accurate.

Anyone else notice this discrepancy? And can it be fixed? I guess that being able to change the wheel circumference in the e8000 system would work I’m but not sure if this is an option.

 

[nicklej]

I know that with e-bikes in general when the charge drops, even slightly, the current also drops meaning that less power can be output by the motor. 5kmh does sound like a fair amount of difference between your gps and recorded motor speed.

There is a chance, as you say, that your circumference could be set too low causing the bike to cut off early as it assumes your wheels are spinning a tad faster than they really are. If possible, have a look into the app and update that info.

 

[Julio]

I have noticed similar stats with my Bosch powered Trek Powerfly LT. Bike showed 71km, Strava said 69km. I asked at the bike shop and the guy suggested that bike is more accurate (based on wheel and tyre diameter to the mm) while Strava is based on GPS satellites that are deliberately set slightly out for civilian use. Not sure that I buy that argument, as google self driving cars (let alone all the GPS based car navigation systems) are surely not that inaccurate.

 

[Gary]

are you runnin the latest E8000 firmware?
the assistance cut out at 14mph (on the E8000 display)when mine was new. with subsequsent firmware updates it seemed to cut out closer to 15mph figure.

non military GPS isn't all that accurate at reading live speed at all as it only records points at one second intervals at most (3 sec for a lot of phones) and isn't very accurate in positioning anyway. (generally only to within 5-10m) Garmin their GPS sports devices are acurate to 15m

 

[ebike_junkie]

When I was hacking mine, I did a before and after test using my garmin watch. They were pretty close.