Easily accessible Kachess Ridge Tr1315 ascends Silver Creek valley to Kachess Ridge and Thorp Mountain.
The typical 18.5mi (3700' ascent) CW loop is really a Silver Creek ride and spends no time on Kachess ridge.
The ride starts with 5.8mi of FR4818, a lakeside gravel road, then a 4.7mi grind on FR4824 and FR115 to the French Cabin Basin TH.
The rest of the ride includes many creek crossings and some hike-a-bike.
This is far too much gravel road to be a destination trail, but would be well worth shuttling.
Unfortunately, any attempt to ascend Kachess Ridge Tr1315 from FR203 will face a 1400' climb in the first 1.5mi, and a final ascent to the FR115 TH which is hike-a-bike as well.
The best non-shuttle option is to ride Kachess Ridge Tr1315 9mi OAB, from the northern TH.
The Kachess Ridge Tr1315 OAB ride is covered on the Cooper River Tr1311 page, but is manageable from the FR115 TH as well, with a 600' Thorp Mountain ascent, then relatively flat ridgeline terrain to the northern TH.
The 14mi (5900' ascent) Domerie Peak Tr1308 to Mount Baldy OAB offers something more epic in a ridgeline ride, but the 2.7mi (2000', 19%) North Peak/South Peak ascent is too steep to climb and too long to hike for most riders.
The southern Domerie Peak Tr1308 Mount Baldy approach is even tougher, ascending 2500' in 2.7mi.
Domerie Peak Trail 1308, Kachess Ridge Trail 1315
Domerie Divide Trail 1308.2, Easton Ridge Trail 1212, French Cabin Creek Trail 1305, Kachess Beacon Trail 1315.3, Little Joe Lake Trail 1330.1, Red Mountain Trail 1330, Silver Creek Tie Trail 1308.1, Thorp Creek Trail 1316, Thorp Lake Trail 1316.1
Lake Easton State Park Campground, Owhi Campground, Red Mountain Campground
Ranking consistently applied to all of the listed trails.