if you want to know where you stack up, find a group ride and rie with others.
How fast you ride by yourself is subject to so many variables, it is pretty much a worthless measure, and when you're riding by yourself it just doesn't matter how fast or slow you are.
I can do intervals with a tailwind and move along at 27mph.
I can do an endurance ride in hilly terrain and average 13mph.
Neither of those numbers do you much good.
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You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.