Sourdough Trail (South)

Trail Meter: 

Sourdough South is a rolly polly lungbuster, traveling north-south and paralleling (but nowhere near) the Peak to Peak Highway.  Solitude and suffering await you... ok, it's really not that bad if you're mentally prepared for high altitude riding with some loose rocks thrown in there.

You can start this trail from the south at the CU Research Center / Rainbow Lakes trailhead, and from the north at the Brainard Lake trailhead. If you cross Brainard Lake Road, then the Sourdough trail continues - we call that section Sourdough North because this section of trail has a pretty different character from Sourdough South.

Sourdough Trail (South) GPX File142.45 KB
Sourdough Trail (South) Google Earth File5.28 KB
Map to Trail Head: 

View Boulder County Trailheads in a larger map

Sourdough Trail (South) Click on image to enlarge
Sourdough Trail (South) Click on image to enlarge

T: 6 A: 7 C: 6

Learn more about BMA Rating
Learn More About Trail Difficulty Ratings
5.9 mi.
1350 ft.


Trail Meter: Good»Fair

50/50 ride and walk on fat bike. The wind has created a lot of off camber sections and sugar snow.

Almost all rideable January 30.
That might change with todays snowfall.

Trail Meter: Fair»Good

Fatbike rideable (and fast!) all the way from Rainbow Lakes trailhead to intersection with Brainard Lake Road. About a mile of slightly rutted, harder to ride conditions past the Peace Bridge, but not bad, and quickly gets wider and better packed closer to Brainard area. Git sum!

Packed in nicely for fast fat biking. Have fun.

Trail Meter: Fair»Good

Almost entirely rideable on a Fat.
Good packed base.

Trail Meter: Fair»Good

Great condition right now

Trail Meter: Poor»Fair

A few spots with water flowing and a couple muddy spots at the north end. All rideable.

Trail Meter: Good»Poor

Starting from the south end I made it 2 miles before getting turned back by drifts.

Trail Meter: Fair»Good

Mostly rideable on a Fat.
Some softer spots midway between Rainbow lakes lot and Brainard.
Use low tire pressures to keep the float.

Soft slippery snow. Lower section isperfect on a fatbike. Softer and less packed after the bridge.

BMA needs your help updating trail conditions. Please register for an account on our website - it's free, fast, and instantly makes you part of the BMA trail community