Upper Mad River Orv Tr1409.1 is a high elevation river ride, similar to W. Fork Teanaway Tr1353, but otherwise uncommon.
Although an 18mi OAB is fine, adjacent trails (Pond Camp Orv Tr1409.2, Blue Cr Orv Tr1426, Lost Lk Orv Tr1421 and Hi Yu Orv Tr1403) create the opportunity to explore nearby terrain without adding a lot of miles or climbing.
The climb rating is just barely 'Intense', and could be considered Moderate.
The Ascent Incline which is given is just for Mad River Orv Tr1409.1, with some brief 10%+ grades on the side trails.
Extending the figure-8 loop to the wilderness boundary of Garland Peak Tr1408 creates an even more challenging ride (38mi, 9600' ascent), although Garland Peak Tr1408 ascent is just an extension of Mad Rvr Tr1409.1.
Easy access and great terrain make the Mad Lake area very popular on weekends so a mid-week ride would be better.
Due to high elevation, the trail is only open from mid July to October, and trail access unfortunately includes Orv so there is that to consider. Feel free to scowl at them as they fling dirt in your face.
Garland Peak Trail 1408, Hi Yu Orv Trail 1403, Lost Lake Orv Trail 1421, Mad River Orv Trail 1409, Pond Camp Trail 1409.2
Alder Ridge Trail 1523, Basalt Ridge Trail 1515, Billy Creek Trail 1416, Billy Ridge Trail 1413, Blue Creek Orv Trail 1426, Chikamin Creek Orv Trail 1534, Chiwawa Orv Trail 1548, Cougar Mountain Orv Trail 1420, Cougar Ridge Orv Trail 1418, Jimmy Creek Trail 1419, Middle Tommy Orv Trail 1424, Nason Ridge Trail 1583, North Tommy Orv Trail 1425, Shetipo Orv Trail 1429, Tyee Ridge Orv Trail 1415
Deer Camp Campground, Goose Creek Campground, Maverick Saddle Campground
Ranking consistently applied to all of the listed trails.