Around here in the Manistee National Forest, the government website claims you can camp anywhere you please, except as some rules perscribe...
Huron-Manistee Dispersed CampingI like to drive the fire trails the USFS cut into the forest for the logging companies to use, just to sight-see. A good 4wd TC would have a great time on these roads, long as you don't mind the mud. You'll be pretty alone except for the odd rubber-necker like me driving by, and the poachers checking you out to see if you're with the cops. Towing a trailer, even a smaller one with a bike on it, I dunno - the fire trails are tight, and often dead end without anywhere decent to turn a rig around.
On State land in Michigan, you can camp for free, but need to fill out a form, put it in a plastic bag and post it to a tree at your site, listing all your contact details for the green-shirts to check up on you.
MI DNR Dispersed CampingThe wider dirt county roads in the forest are usually privately owned on both sides, even though you're in a National Forest, there's a lot of private property :( When I worked as a census taker, the folks living on plots of land deep in the forest weren't happy to receive visitors unannounced.
