In 2001 I biked the Truck Trail from Grand Marais to Muskallonge Lake. I didn't walk any of it, handled the sandy road just fine with 47mm tires on a recumbent bike. I remember it being a lonely ride through forested rolling hills.

At that time there were also 20 unpaved miles between Munising and Grand Marais. That section was more difficult. I pushed the bike through the biggest sandy sections and crashed a few times in deep sand. Fortunately it's a soft landing when you crash on deep sand.

I've had a few people warn me about this stretch. Each time I'm concerned my memory is bad. This time I've gone back and made a map. I switched to satellite view and zoomed in at the road in random places. Every place I examined had a paved road with lines.  

There is also a trail right along the cliff. Perhaps that is what people are warning me about? 

As a side note: Boat Tours of Picture Rocks are currently canceled. Perhaps that will change between now and July. It is interesting that the person who gets seasick easily (me) is interested in the boat tour . .  .

When I was investigating this a few months ago, I was assured by several locals that the road between Grand Marais and Munising was now paved, a relatively recent development. I've seen more than one journal that bemoaned the condition of the unpaved road. I was warned against the Grand Marais Truck Trail, which remains unpaved, with sections of soft sand or gravel that make it difficult for biciycles.

The trail along the cliff is  the North Country National Scenic Trail which crosses 8 states from New York to North Dakota. The 42 mile segment in the National Lakeshore is a hugely popular backpacking route. Bikes are allowed on some parts of the North Country Trail but it appears that bikes are prohibited on the busy trail in Pictured Rocks National Lakeshore.
Hopefully the Pictured Rocks boat tour will be running again by summer.

We too are planning to take the slow ferry....Patrick also is inclined to sea sickness

take Dramamine .