In Mountain Biking Colorado's San Juan Mountains, Robert Hurst describes "the terribly difficult climb to Windy Pass. This three-mile ascent is ultra-technical and largely unrideable for the average cyclist."
No worries. To enjoy this trail, the rider has only to visualize a three mile uphill hike. By hiking standards it is so mild that you might as well roll a bike along. With this simple reframing you have prepared yourself mentally and spiritually to enjoy those sections of the uphill where you'll be able to ride. Which are, admittedly, few.
Soon you'll encounter interminable roots. Big trees require big roots. It's a plant thing. In one of his whimsical asides, Hurst speculates that the volume of pedal clipping and unclipping this trail requires may disturb wildlife. There is a simple solution: flat pedals!
Getting there: The trailhead is on the eastbound side of Rt. 160 and is marked by a sign. A small-ish pulloff is directly opposite or you can park uphill a few hundred feet at the Treasure Falls area. Either way be careful on this busy highway.
Looking up through the aspens around the one mile point you'll see the "Bootjack" rock formation up close.
At about 2 miles, stay right. You'll go South to a broad switchback, then East up the final grade.
Gradually, the grade lessens and you arrive at Windy Pass. The trail continues on down the other side through open meadows to intersect Treasure Mountain Trail.
At the pass, you have two excellent options: cruise or bumps. For cruise, just continue on down Windy Pass trail to Treasure Mountain trail. This is superb flowing singletrack with just enough bumps (roots, of course) to keep your suspension warmed up.
For bumps, just plunge back down the way you came. Obviously, you'll be spending a lot of time in the "attack position".
Either option is an excellent and well-deserved downhill ride.