Bosch limiter accuracy? User setup options?

[qwertycube]

My CUBE Reaction EXC finally turned up, so I was able to go out with my wife on her new Trek Powerfly 5. Right away I noticed something was very different. Although both bikes have the same Bosch Gen4 and Purion, when mine cuts out at 15mph, my wife’s is only showing 13.9mph. When I’m pushing 16, my wife isn’t even trying! It makes a painful difference.
My wife’s bike has 27.5 wheels, mine has 29. Surely this is not just a tolerance issue, the difference is too great? it must be a calibration setting in the Purion? But no user setup menu on the Purion? Any advice?

 

[Beekeeper]

My CUBE Reaction EXC finally turned up, so I was able to go out with my wife on her new Trek Powerfly 5. Right away I noticed something was very different. Although both bikes have the same Bosch Gen4 and Purion, when mine cuts out at 15mph, my wife’s is only showing 13.9mph. When I’m pushing 16, my wife isn’t even trying! It makes a painful difference.
My wife’s bike has 27.5 wheels, mine has 29. Surely this is not just a tolerance issue, the difference is too great? it must be a calibration setting in the Purion? But no user setup menu on the Purion? Any advice?

increasing tyre pressure would help but I’m not sure by how much