The Dallas trail starts about two miles north of Ouray. It climbs a brutally steep and unrelenting hillside for 3.5 miles at an average 12.7% grade. Descending is a hoot, but the lower switchbacks are awful. The climb is really too steep to be worth the effort. This trail is best used as a descent down after climbing from the Ridgway area. If you decide to tackle it you'll get a trail that is almost 100% singletrack, shaded in the summer, with great views.
From Ouray or Ridgway, turn off of US 550 on and cross the river just south of Dexter Creek or two miles north of the hot springs pool. After crossing the river head north and follow CR 17 for 0.4 miles to the trailhead on your left.
The first 1/2 miles will make you want to quit. There is a turn off for Corbett Trail at 0.9 miles, stay right on the Dallas Trail
(no bikes on Corbett). When you think the brutal climbing is over, it keeps going. Climb another 1.6 miles up to another intersection with the Corbett trail and stay right again. Keep climbing another 1.4 miles to a high-point at Moonshine Park. The views here are spectacular.
From Moonshine Park you can continue another 0.6 scenic miles to the Burn Ski Hut, or turn back and rip the descent back to the car. Be careful of the cliffs on the lower switchbacks. Watch out for hikers on their way up. Sliding out there could get you badly injured or killed.