The person that will the most accurately estimate the maximum speed (in km/h) that the speedometer of my bike is showing at this moment will be awarded a dinner at Fresca (or some other nice place on old continent if one of my European friends will be the winner) in my company.
Two factors you might want to take into account:
1. I installed the speedometer one month ago and during this time I only biked in the city.
2. There are many hills in SF (but also there are many stop signs and traffic lights even on the roads going downhill…)