Go with the flow! Since about 10 to 11 years of age I could do 30mph easily.
I discovered this on a crappy folding bike with 2-speed duo-matic, while being in a hurry and thus angrily overtook a slow Citroen 2CV :-)
Looking at the speedometer from the outside. Showed 50kph, so I must have been faster, or the speedometer slightly wrong.
Whatever, that experience has shown me that I could do that, and from there on
it was in my 'muscle memory', ready to be used at will.
Which then went up to 40/41 on road bikes on flat grounds with no headwinds, for about an hour sustained. But I often did 44 to 47, always trying to push the needle of my speedometer as long as possible to the right.
Downhill easily 50 to 55. Highest speed ever(downhill OFC) was 95kph, which is about 59mph. Still doing that sometimes, but less often nowadays. Need to be in the Rockies for loong descents, weather has to be good, streets mostly empty, which they aren't when weather is good, and so on.