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South Sourdough (#835)

Intermediate/Difficult Intermediate/Difficult
 3.7 (45)
  1. Areas
  2. CO
  3. …Front Range
  4. Nederland
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“Sourdough Trail (South of Brainard Lake) ”

Alan Doak
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5.9

Miles

9.5

KM
Singletrack

10,274' 3,132 m

High

9,217' 2,809 m

Low

1,121' 342 m

Up

265' 81 m

Down

4%

Avg Grade (3°)

20%

Max Grade (12°)

Dogs Off-leash

E-Bikes Not Allowed

Description

From the Peak To Peak Highway, take the exit for the CU Alpine Research Center and park at the trailhead on the left. An outhouse is available at the parking lot.

The trail climbs up singletrack to the Brainard Lake road, which splits the southern and northern halves of the Sourdough Trail. The southern half of Sourdough is less technical than the northern half, and travels through splendid forest that rarely opens up enough for a vista.

This first two miles is a climb up fairly loose rocks and will keep you on your toes, though it's all rideable. The grade isn't too steep, but there's not much of a break until you get to a pretty bridge over a stream crossing at 2.5 miles.

The trail becomes smoother and faster at this point, but keeps climbing for a while with occasional views east through the trees. After about 3.5 miles, the trail becomes flatter and much faster to the end.

To return to the trailhead, either ride back on the trail or along the Peak To Peak Highway.

The trail is typically rideable (or mostly rideable) by the first week of June. Any sooner than that and you'll quite possibly be pushing through snow.

Contacts

Local Club: Boulder Mountainbike Alliance

Nov 17, 2025: Trail Update: South St Vrain

Nov 14, 2025: Another Step Closer to new Betasso Connector

Oct 24, 2025: Boulder County Moves One Step Closer to a Safer Boulder-to-Betasso Connection

Land Manager: USFS - Arapaho & Roosevelt National Forests Office

Shared By:

Alan Doak with improvements by Richard Hackett
Full Details

Trail Ratings

  3.7 from 45 votes

#1

in Nederland

#463

Overall
  3.7 from 45 votes
5 Star
20%
4 Star
38%
3 Star
33%
2 Star
9%
1 Star
0%
Trail Rankings

#1

in Nederland

#143

in Colorado

#463

Overall
22 Views Last Month
10,370 Since May 2, 2013
Intermediate/Difficult Intermediate/Difficult
0%
0%
20%
32%
48%
0%
Add a Photo

Photos

Perfect late summer conditions
Sep 20, 2021 near Nederland, CO
Winter means fresh tracks on the climb from Rainbow Lakes along South Sourdough.
Feb 18, 2017 near Nederland, CO
Peace Bridge in February has 3+ feet of snow!
Feb 23, 2017 near Nederland, CO
Bridge crossing and a good rest on the Sourdough Trail
Oct 15, 2014 near Nederland, CO
Sourdough (South) - Brainard Lake and Peacefull Valley - Ward - Colorado
Aug 7, 2024 near Nederland, CO
One of the few peeks through the trees.
Oct 15, 2014 near Nederland, CO

2 Comments

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Weather

Current Trail Conditions

All Clear 23 days ago
Add Your Check-In

Check-Ins

Jun 11, 2026
Zachary Potter
A rocky climb trail with a moderate grade. A couple spots were tough enough that I had to walk up instead of ride
Jun 26, 2024
Matthew Sharpe
5.9mi — 1h 30m
Jul 3, 2022
Frank Selker
Aug 28, 2021
Andy Dog
A lovely ski trail. Would be sweet on a horse. No true expert moves but minimal flow due to many axehead sized rocks and roots. Not sure if I had fun 5.9mi — 1h 00m
Aug 5, 2020
Nicholas Horan
Over handlebars and injured 0.5mi — 0h 15m
Jul 4, 2020
Corbin Cowan
Aug 19, 2019
Jon Banks
A bit chunky but fun. Bikepacked from Ward to Ned
Jul 11, 2019
Paul Billings

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