That depends. When the ground is dry or damp, the terrain can often easily be ridden on street-biased adventure tires but when it rains, even more aggressive knobbie-style tires may have a difficult time gaining traction in wet grass and mud.   It's important to note that it has been our experience that the least-experienced riders commonly arrive with the least-capable tires and ultimately struggle unnecessarily and/or hold back the entire class when it could have been a simple solution to arrive with tires that ensure they would get the most out of their investment in time and tuition. Due to this pattern, we have implemented minimum standards with recommendations. A complete list of tires and our recommendations is found here.