An easy one:

LMAO!!!
Do you have it calibrated properly? As in, did you measure your wheel circumference and configure it?
Because 65 Km/h is pussy!!! 
I don't have a speedometer mounted anymore, but I could (easily) get 70+ on descends and that on a MTB!!!
70 on mtb? I don't believe you, unless you have 5 km straight descends in Ger.
Even in professionalism, you must rotate legs like crazy to achieve 70-80+.
Don't have a picture now. Got distracted.