Bosch Purion over-reads speed by 2km/h

Snoozeboy

Member
Feb 20, 2019
104
56
Lausanne
Hello, I have a Cube Stereo 140 with a Bosch motor and Purion display.

I noticed that the Purion seemed to read 2km/h slower than the read out on my phone/satnav. Now, I've bought my wife an eMTB so she can keep up with me on rides, but she's more than doing that - my Bosch system is cutting off assistance 2km/h lower than her Yamaha PW-SE (Haibike Nduro 1.0) so she's right up my arse heckling me to go faster.

Is it possible that the system is set up for 29" wheels, when mine are 27.5s? Is there any way to correct it? I've fiddled with the sensor on the spoke, but it seems that it's more likely to under-read if it's in the wrong place.
 

Snoozeboy

Member
Feb 20, 2019
104
56
Lausanne
I took it to the shop and the lbs guy moved the "slider" in the software such that the wheel diameter was smallest (I guess for narrower tyres).

Now the assist cuts at 24.8km/h whereas it used to cut at 26.5. The speedo still over reads by 2km/h and my wife still heckles the fat bastard in front to hurry up.
 

Frankieboy

Well-known member
Jan 14, 2019
293
225
Basingstoke
I have two bikes with Bosch / Purion display, both show I’m going 1-2 mph faster than my sat-nav. However, the assist doesn’t cut out until 16.5 - 17 mph, so around 15.5 mph on the sat-nav which is correct.

Could it be that your wife is fitter and can therefore pedal harder when the assist cuts out?

Have you considered derestricting?
 

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