Reddit user TezzaMcJ has created a visual off-road trail guide for the areas in GTA 5 around Mt. Chiliad. It includes a map of the area, with the main trail labeled, a list of vehicles that work the best, and numerous trails marked according to difficulty.
If you’re interested in giving it a try, you can use the guide to quickly tell which routes have beginner-level difficulty, which have intermediate, and which have advanced. It also includes paths for limited cars, paths that haven’t been completed, and “extreme terrain,” all clearly marked.
Check it out and see what you think!