Bicycling/Fixing Gearbox in Mountain Bikes.
Is it possible to fix Gearbox in Mountain Bikes?.
If yes, What Speeds can be achieved by the cyclist?.
What do you mean exactly mean by an gearbox.
There are 2 possibilities, a gearbox from Rohloff of an "gearbox" of shifing by an deraileur and cogs.
The speeds who can be achieved will be depending from the rider, kind of road, condition.
In a downhill you can easily get an speed of more than 100 kilometers an hour, Eric Barone sets an record on a hill of 173 km/hr. On a snowy/icy hill a record of 223 km/hr.