The entrance road is hard to find - Drive to the Indian Hot Springs facility in Idaho Springs, take Montane Road. It turns into Hidden Wilderness Road when the pavement ends.
As already stated by others, this is a Jeep trail. Do not attempt without 4WD at any time of year. It’s dangerous to turn around, and the trails kinda busy. You could get in a bind here if you’re not careful.
There are multiple campsites along the road, one at each switchback, and at least a dozen on top of the mountain. Campsites on top are large, wooded, and spread out. The switchback spots aren’t as good. I was able to find a flat spot up top big enough for a 10x10 tent, but I had to look around a bit.
If you keep following the main “road”, it eventually ends at a private gate, and you’ll need to turn around and backtrack about a quarter mile to get a camping spot.
I spent 2 weeks here in a full size 4x4 pickup with stock suspension, drove up and down the mountain about 5 times, slowly, without issue.
I probably wouldn’t drive up there in a Subaru, but I did in fact see several Subarus up there on weekends.
This is a popular place for locals to shoot guns and ride dirt bikes. There are brass shell casings on the ground literally everywhere, and a LOT of shooting most days. More traffic than you would think on such a treacherous road, almost all locals coming up for the day.
Saw a couple of NFS maintenance trucks, no rangers or other staff. Peaceful spot at night. I’m a remote worker, and Starlink and Verizon both have good signal. Firewood everywhere. No water, rivers or lakes, but otherwise no complaints.