Hey ya'll, a little FYI regarding trails on the Manistee National Forest...
"ORV" is a generic term; an ORV could be a truck, a jeep, a quad, a dirt bike, or whatever. On the National Forest, the ORV trails are open only to ORV's 50" wide or less, and meet the legal definition of an "ATV". If you are bored, you can look up the Michigan legal definition of an ATV, but to paraphrase this means dirt bikes and quads. If you are taking a piece of equipment that is 51" or larger down a trail on the National Forest, then you are illegal. Referring back to what the one guy was saying...the ability to make your vehicle squeeze through does NOT make you legal.
The ORV trails on the National Forest, at least the portions from Baldwin south are marked with orange triangles with a dirt bike or quad icon, and there are usually posts, signs, or maps where trails cross larger roads indicating that it is a trail open to motorcycles and/or quads and is closed to all other motorized vehicles. Bottom line, if you are caught on one of these trails on something wider than 50", you are subject to fines and maybe also a mandatory court appearance. The only things subject to interpretation is how many different things you can be ticketed for...
As far as ORVing on other parts of the forest, if it's legal for any vehicle to drive down it, then you are generally okay; provided you aren't tearing things up...but this is another area subject to interpretation...if a ranger, CO, or other officer comes along and determines that you are damaging resources, then you can be ticketed, even if you are operating a legal vehicle on a legal route.
Bottom line: if you wanna know where to operate an ORV on the National Forest legally, then you need to call the main HQ office in Cadillac (231-775-2421), or one of the district offices in Baldwin (231-745-4631) or Manistee (231-723-2211). On the east side of the state (the old Huron NF portion) there are district offices in Mio (989-826-3252) and the Oscoda area (989-739-0728).