What is a bike marathon called?
There is no official term. The nearest you could get would be
"bikeathon" and to be roughly equivalent to a marathon, it would
need to be at least 100 miles or 160km.
A marathon is a running race, named after the distance reputedly
run after a battle in ancient Greece to deliver a message to Athens
that the battle at marathon (25 miles/40kms away) had been won. The
race was introduced for the first time at the modern olympics and
then standardised to 26 miles & 385 yards (42.195km) after
1921.
The term marathon is often misappropriated to uses other than
running, to indicate anything long or demanding of endurance. All
of these other uses, including biking, have no standard definition
and are slang or common usages. A bike marathon has no official
name because there is no bike marathon distance.