Bicycling Magazine

Boulder, CO: Sourdough Trail 

A Colorado altitude thrill ride, this 11.5-mile out-and-back snakes through tight conifer tunnels, navigating rock gardens, log piles, and balance-testing switchbacks.

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Author: Bicycling Magazine
Date: 2 Sep 2008 9:19:52 PM
Activity: Mountain Biking
State: Colorado (CO)
Distance: 11.48 mi  (Change units)
Survey Elevation: Total Gain: 2717 ft
Total Loss: 2719 ft
Net Change: -2 ft
Difficulty: 7 / 10
Tags: Boulder, Colorado, Denver, Nederland
Rating: Unrated   Rate it

A great choice at the height of summer, this high-altitude route starts at a refreshing 9,000 feet and is well shaded by the conifer and aspen trees lining the eastern slopes of Niwot Mountain. This 5.25-mile stretch of the Sourdough Trail (running south to north between the CU Mountain Research Station and Brainard Lake Road) offers an opportunity for intermediate riders to build skills and fitness while allowing skilled riders a chance to test their limits as well.

Riding south to north, the real test of this ride is the first 3-4 miles, during which the trail gains over 1,000 feet of elevation on relentlessly rocky singletrack fraught with will-testing switchbacks. After the bulk of the climbing, rock gardens and log piles remain to challenge before the turnaround point at Brainard Lake Road.

There are more trail options on the north side of the road, but cleaning the return trip to the parking lot requires a fair bit of concentration and strength in its own right. On the drive back to Boulder, hit up the Mountain People’s Co-Op in Nederland for a fresh peach and a hearty bag of trail mix.

-Mapped by Mark Harrison

TO TRAILHEAD: Head west on CO 119/Boulder Canyon Dr. for approximately 15 miles to Nederland. Take the second exit from the traffic circle, heading north on CO 72/Peak to Peak Highway. Continue 7.1 miles and turn left on CR 116, heading toward the Mountain Research Center. Trailhead parking is 0.5 mile down the road on left.

Position Format: Datum:

Sourdough Trail

Distance: 11.48 mi Points: 1550
Total Time: none Speed: 0.0 mph Pace: 0:00 / mi
Active Time: none Speed: 0.0 mph Pace: 0:00 / mi

Points of Interest


Location: 40.027933, -105.524907
The trailhead is accompanied by a detailed trail map, a restroom, and an abundance of parking.

Babyhead Climbing

Location: 40.036059, -105.529046
The first 3-4 miles of this trail present both a physical challenge (with over 1,000 feet of elevation gain) and a technical test (with nary a smooth stretch of singletrack and plenty of tight, rocky switchbacks to navigate).

Rock Maze

Location: 40.045752, -105.545611
A maze of momentum-halting, knee-high boulders awaits at the bottom of a brief descent. Sure enough, the climbing ramps back up after this creekside obstacle.

Switchback Grind

Location: 40.046902, -105.544581
The lungs will really start to burn as you surge up the final pair of steep switchbacks.

Tight Switchbacks

Location: 40.046844, -105.546448
The switchbacks are tight, but not impossible. A great training ground for intermediate riders looking to find their groove going up and down these kinds of hairpins.

Log Pile

Location: 40.048873, -105.539882

Peak to Peak View

Location: 40.052322, -105.539303
Near the trail's highpoints, a clearing in the trees offers an overlook of the Peak to Peak Highway and the Boulder foothills to the east.

Little Raven

Location: 40.075141, -105.533166
Continue straight toward Brainard Lake at the Little Raven Trail Junction.

Rock Garden

Location: 40.075929, -105.533702
The final true technical test before the turnaround, a rock garden at the base of a small rise seems to offer a variety of different lines. It may take a few stabs before you clean it, but it's certainly doable.

Brainard Lake Road

Location: 40.080206, -105.534110
This track turns around at Brainard Lake Road, though there are more options (the Wapiti Trail, the South St. Vrain Trail, and the northern Sourdough Trail) from the Red Rock Trailhead on the north side of the road.


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