To do this ride as a loop, park at the Icicle ridge trailhead, and ride 8 miles up Icicle river road to the 4th of July trailhead. Now you will have to climb almost 5000 feet to get to the top of Icicle ridge. Expect to carry your bike for a mile or two. The rest you can either push or try to ride. Either way the climb is brutal.
Once you get on the ridge, the views of Stewart Range are incredible. The descent is totally rideable but somewhat sketchy in places - lot's of rocks and some brush.
How to get there:
If you take US2 from Seattle to Leavenworth, turn left on Icicle river road at the first gas station. The Icicle ridge trail head (where you park your car) is about 2 miles up that road on the right.
Make sure you have enough water. There is no water on the ridge