You might want to learn more about the wilderness act and why it came to be.  Of course, Mtn biking was not a form of recreation then, but even if it had been, it would not be consistent with wilderness.  You might want to learn more about silviculture too.  Selective thinning has failed to work time and again over the last 100+ years because it is not a panacea for all types of forest.  Designating more wilderness is not always the answer either, and, as you note, it restricts existing uses like some forms of recreation.  But do you Mtn bike in the proposed Crater Lake Wilderness?