Dream about riding mountain bike indicates your indecisiveness. You need to be more vocal. You are being shielded from some information. This is a metaphor for your attitude or the various roles and responsibilities you have in your life. You believe that you can do a better job if you were in charge of things.
Riding mountain bike dream is a signal for your understanding of your subconscious and its motivation. Perhaps you are getting involved in some issue where you are not wanted. You need to better focus on your goals. This dream points at your political views. You are looking for a change or for something new.
If you dreamt about riding mountain bike:
You were once a creature of reason. For you, everything had an explanation, a reason to exist, and a place in the world. You never missed a chance to share your viewpoint. Then all of a sudden, silence. Perhaps you needed to get some perspective, not necessarily on the things you know, but on how you express that knowledge. Now words have come back into your life and your ideas are more moderate.