Another point to consider if you are driving your NV200 on even mild gravel roads is the really mickey mouse OEM 185/60R15 tires.
If you ever dismount 1 of the JK Tire Americargo tires you will quickly realize how small and light there are. The sidewalls are extremely thin and will not hold up to a gravel road.
Plus the un-siped tread pattern and very mild tread pattern provide no traction. I can't imagine how poor they would be on a muddy road.
BTW, these narrow tires should easily cut thru water and rain but they are actually terrible on wet roads. This is because the tires have no siping. These narrow tires are worse in the rain than the much wider 255/40R17's on my Mustang.
The narrow OEM tires also provide no rim protection. As can be seen the rim lips are exposed due to the narrow tires. There have been several reports of bent rims due to the narrow tires.
So, if you really driving are your NV200 on gravel/rough roads, the 1st thing to do would be to upgrade the tires.
Which tires to install is an entire other subject. I will be upgrading my NV200 tires this fall for winter and will report my findings...