Upvote:1
The Ontario Federation of 4WD Recreationists maintains a trail index, which is unfortunately accessible to their members only (joining costs $50). The trails listed there are graded according to their own rating system which covers difficulties ranging from 1 Maintained Dirt Roads
to 5+ Impassable trail
.
In addition, Ontario Trails lists many trails for free, as you mention. Trails are not classified by difficulty. However, you can click on Trail Details and see if the surface type is listed. This should give an indicator of trail difficulty. For example, below is the trail details for the Forgotten Trails: