FATMAP difficulty grade
A state of the art mountain bike race or route in the Upper Peninsula of Michigan from Marquette to Ishpeming.
What is 'state of the art' about it? Well, some of the most abusive, punchy, hill-infested, rocks, roots, steep climbs, impossibly technical descents terrain anywhere on the planet.
Good luck averaging anywhere near 9-10 mph, more like less than 7 mph.
If doing this for fun and not on race day, maybe you should just ride it over 3-4 days, taking it in 13-18 mile chunks, which ride like 30 milers! Remember, this is what mountain is supposed to be.