Bosch purion speed inaccurate

[Errol1098]

Hi,

Im having an issue with a Bosch CX motor in that the speed on the purion display is around 10-15% inaccurate. when the speed reads 26klms/h and the assistance cuts out the bike is only doing around 22klm/h checked @ganst my Lezyne computer and an iPhone app. Wasn’t a problem initially as my wife had same bike and motor but now she has a Specialized Turbo levo it really stands out and on long inclines she just smokes me as her motor speed matches real time speed. I emailed Bosch and they said I should take it to a dealer and check the wheel size has been set correctly but my wife’s older bike has the same inaccuracies and hers runs 27.5” to my 29” 2heels so not sure that is the issue But will drop it in to a dealer and check. Does anyone else have experience with the Bosch not reading correctly?
THANKS

 

[Zimmerframe]

On the purion display it normally reads about 1.5k too fast. I think they did this so you feel like you're still getting assistance over 25kph as the slowly eases off the help.

Whenever Iv'e checked, the actual speed (using GPS) is exactly 25kph that it cuts out at.

Yours sounds quite a long way out and the wheel size theory could fit.