Here's a link to MT state law pertaining to bicycling. I personally like to keep this handy.
This is the most important part (in my opinion).
(2) A person operating a bicycle upon a roadway at less than the normal speed of traffic at the time and place and under the conditions then existing shall ride as near to the right side of the roadway as practicable except when:
(a) overtaking and passing another vehicle proceeding in the same direction;
(b) preparing for a left turn at an intersection or into a private road or driveway; or
(c) necessary to avoid a condition that makes it unsafe to continue along the right side of the roadway, including but not limited to a fixed or moving object, parked or moving vehicle, pedestrian, animal, surface hazard, or a lane that is too narrow for a bicycle and another vehicle to travel safely side by side within the lane.