0_Apprentice
I really love mountain bikes, how about you?
1_Wizard
I have a friend that does it - they are a bit different from regular bikes as they are enhanced for durability and performance in rough terrain.
0_Apprentice
That is true, they have special wheels that allow the bikes to perform better on and off trail.  Biking on the beach is off trail too, and that is hard!
1_Wizard
She rides hers mostly on mountain trails, fire roads and other unpaved surfaces.
0_Apprentice
That's great.  It's great exercise.
1_Wizard
I didn't realize they were popular with couriers who have to navigate potholes and over curbs also.
0_Apprentice
I did not either!  Come to think of it, I have seen couriers with some sturdy bikes.  They are mountain bikes for sure.  I actually had a ten speed and was hoping to have a tire that was more like a mountain bike - because of the pot holes!  I could only get normal tires for it.
1_Wizard
There have been a lot of subtypes of mountain biking, such as cross country, downhill, track and slalom - so it's pretty popular