Is it acceptable to mountain bike on narrow hiking trails?(Minnesota) I've recently been getting more into mountain biking. I like to take my bike out every so often onto unpaved trails, but the closest designated mountain biking trails in my area are not a short trip away.

However, there are several un-paved trails that are within my area that are not designated as solely hiking or biking trails. I've been taking my bike out on these trails recently, but am worried if what I'm doing is acceptable practice. A lot of the trails I tend to go on are narrow trails that are wide enough for a single bike to ride on. It feels that if there is a hiker on the trail, there is very little room for them to pass if I yield.

This made me wonder if there were any regulations on biking down these trails. I know that larger parks designate their trails for either biking or hiking, but is it right to assume that small parks that have no noted designation on their trails can be used as a shared trail?
It depends on the local laws, both regional and countrywide. It's not really a question of acceptable or not.

e.g In England trails can be strictly footpath which means no bikes. Bridleways, Byeways and Byeways Open to All Traffic (BOATs) can be ridden by bike with pedestrian priority.

Find out the local laws for your region. 

If you do find that all your local trails are fair game it's still up to you to ride in control and with courtesy. Any person &amp; bike collision will be your fault.