Originally Posted by
Campag4life
Thought I would posit a question to those that have thought about it. This question is part comedy but nonetheless rooted in reality aka aerodynamics...
When wind is say 10-20 mph and a route is out and back...my route is generally 10 miles + North and then 10+ miles South return. When the wind is dead downwind one direction and a pure headwind back, how much does average mph vary for the round trip compared to the same route on a dead calm day?
Assume zero rolling resistance, just aerodynamic drag and cyclist who can maintain 20 MPH air speed.
Riding 20 miles out then 20 back in no wind takes one hour each way, two total, and yields a 20 MPH average.
Riding the same with a 10 MPH wind along the course allows a 10 MPH ground speed into the wind taking two hours, 30 MPH ground speed with the wind which takes 40 minutes, and 40 miles in 2:40 is a 15 MPH average.
Rolling resistance makes the arithmetic more complex and slightly reduces the speed difference changing directions.