been riding bikes for 33 years daily (up to 65km/h every morning last year (ok 50+km/h for 1 km on light slope on the journey to be honest)) and I am as clueles

been riding bikes for 33 years daily (up to 65km/h every morning last year (ok 50+km/h for 1 km on light slope on the journey to be honest)) and I am as clueless as you. Displayed information is basically the speed you have for given the size of the wheel, given the rpm (turns per minutes) for each gear and plates. In school you learn stupid stuff like C = 2pi(R+dr) (R=size of wheel (70cm) + tire (2.5cm) you take the ratio of plate/gear and deduce your gear by making rpm * 2 * pi * (R + dr ) * number of teeths on front / nomber of teeth back. It is basic math. You can express everything in SI and apply (m/s) x 3.6 to get km/h. If you do a bit of mental calculus it is easy. If you actually ride bike it is useless, after some years, your legs know stuffs. Like the fashion of compact pedalier is freaking stupid and it is impossible to find a decent bike that is not overpriced in north america since lance Armstrong won the tour de france, and that it has put a lot of douchebags with too much money and not enough civility on bikes. But I guess this if off topic... Like the fact my wife and I nearly die every day commuting on our bikes and that we have at least 2 accidents a year. Sometimes with people in SUV going out of town with their 11k$ bikes attached at the rear.