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Level: Intermediate
Length: 12 mi (19.3 km)
Surface: Singletrack
Configuration: Out & Back
Elevation: +409/ -108 ft
Total: 161 riders

Mountain Biking Sourdough Trail

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#164 of 1,362 mountain bike trails in Colorado
#1,182 in the world

This section runs between 9200-10200' elevation. The altitude, climbs, and constant rockiness make this an overall tough ride. There aren't many large-rock sections, but plenty of small-medium ones to keep it a little rough most of the time, and many small sharp ones that have given me pinch flats and holes in the sidewalls. As of 2012 it seems they've done some trail work and smoothed out several sections that where once much harder. There are several fallen trees you'll have to work around, some have been turned into fun little log piles to ride over. The ride is mostly through dense forrest perfect for hot summer days. There are maps at both ends of the trail, check out the map at the north end to see more trail options that continue from the trailhead on Brainard Lake Rd.

First added by on Apr 12, 2005. Last updated Apr 30, 2020. → add an update
Before you go
  • Drinking water: unknown
  • Lift service: unknown
  • Night riding: yes
  • Pump track: unknown
  • Restrooms: unknown
  • Fat bike grooming: unknown
  • E-bikes allowed: unknown
  • Fee required: unknown
This trail information is user-generated. Help improve this information by suggesting a correction.
Getting there
From Boulder, head up to Nederland. Go right(north) on Highway 72 for about 7 miles. Turn left onto County Road 116 (there's a sign for the University of Colorado Mountain Research Station). go about .5 mile to the parking lot on the left, trail starts across the road, this is the south end of the trail.

To get to the North end of this section, head towards Ward, on the North end of Ward on highway 72 you'll see signs for Brainard Lake Rec area, head up that way 2.5 miles and there's a large nice parking area on the right, just before you reach the fee station.

http://maps.google.com/maps?q=nederland, co&hl=en&ll=40.027549,-105.524712&spn=0.036871,0.06669&hnear=Nederland, Boulder, Colorado&t=m&z=14

There's another trailhead further north, from Ward, head up Brainard Lake Rd, there's a large nice new parking area on the right just before you get to the Toll gate. For this stretch of Sourdough, most of the climbing is done heading North from the South end, and mostly downhill going South.
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Sourdough Trail Trail map

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Matthew_Cory (on Oct 6, 2019)
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Good (on Sep 29, 2019)
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Rider questions

Q: How rocky is the trail?

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  • Jmurphy8776

    No doubt this is a rocky trail but what makes it nice is the consistency. The overall uphill from the south trail head is very doable and you just put your head down and pedal, making it through the rock and root sequences.

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  • n25

    all around great

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  • interrobangart   ✓ supporter

    I rode this a few times when I lived in Eldora and thought it was a really nice trail through a beautiful section of wilderness. It definitely has loose rocks, and rocky rooty sections like everyone has mentioned, and it is all fun. I've rode it on a hardtail with front suspension, and my all rigid single speed. The rigid 1x1 was more fun for climbing and technical areas, but having the front suspension was nice when I needed speed to get back to my truck to beat a wicked thunderstorm that was chasing me on one ride. (Yes, be prepared for thunderstorms, they come out of no where!)

    Not sure if anyone else mentioned it, but the trail actually goes past Brainard Lake all the way to the Buchanan Pass/Camp Dick road at Peaceful Valley. If you have the time to do the full trail, check it out. I don't recall the mileage for the full out & back, but I think it took me around three hours or so which included snack breaks and just enjoying the scenery.

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  • *****

    A lot of climbing from the trailhead. Very fun but will leave you gasping for oxygen (if you're a flat lander). At the top, you'll get to the Gateway park entrance. Two miles on the road and you'll get to the Brainard lake. Nice little 4 mile loop around the lake, then head back down Sourdough. The descent is fun and fast.

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  • FinishSTRONG7

    A ride relatively close to the Boulder area with the atmosphere of an alpine singletrack ride! You see yourself in the middle of a vast and dense forest, yet you can easily hear the traffic from State Highway 72 to your right on several occasions. The first two miles are definitely the toughest. However it is mostly doable for any strong climber, just a couple of short highly technical sections. The reward for that work is smoother singletrack practically the rest of the way! Nice view of North Boulder, Boulder foothills, and the Eastern Plains in between the trees about halfway through. It is approximately 6 miles from the trailhead to Brainard Lake Road, but plan on at least 3 hours to finish an out and back ride.

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  • jkey6

    This trail is really great. The dense vegetation makes this a very different experience from the bone dry trails around Boulder and Golden. It's not quite as fast and buffed out as other front range trails but that's because it isn't traveled nearly as much. The solitude makes this trail worth the drive. I have only done it as an out-and-back from Rainbow Lakes to Brainard Lake (12 miles round trip) which I think is a good way to do it since you do most of your climbing the first half and enjoy the tight and moderately technical singletrack on the way back down to the car. I only say moderately technical because the rocks and roots are generally pretty small, but make no mistake, there is PLENTY of loose rock on this trail. This review is for Sourdough South only (south of Brainard Lake trailhead).
    P.S. Check the weather before you go! I got caught in a surprise thunderstorm.

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  • abegold

    Nice ride in the woods. The altitude makes the climbing tougher. Compaired to other places I've ridden didn't find the rocks a problem.

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  • pickettz

    I was riding this trail this past fall, and I almost died. Not because of the trail, most of which is covered in loose rock (actually a very fun trail), but instead because of moose. Flying down the single track back to the car park, a calf ran out into the trail about 15 feet ahead of me and continued to run straight down the trail. Luckily I was able to slam on the breaks because the doe followed the calf onto the trail, and was about 4 feet away from t-boning my bike. And to think, the one time I don't have my helmet cam with me!

    Overall, check this trail out.

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  • tickledpickle

    This trail is more of an intermediate plus, borderline advanced. Very rocky and bumpy, on the way down, my hands were numb and sore. Great trail for a hot summer day as it's surrounded by woods. Going up, it's almost constant climbing. First mile or so of the trail is covered with loose rocks and sandy gravel.

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  • John Fisch

    Some rocks are amusing, some are annoying; this ride has plenty of both. And roots. I wouldn't want to ride a hardtail here (unless maybe if it was a 29er). The combination of altitude and rocks provide a physical challenge, but the grade is generally pretty easy, so it's all doable. This one trail has lots of options; it's great as an out-and-back (the descent is way fun), a point to point with a shuttle from Peaceful Valley, a loop if you don't mind a long stretch of pavement with more climbing, or you can connect to many trails in the extensive South St Vrain network.

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  • mwalsh23

    Absolutely awesome. This trail is rocky, there's no question, but it's not bad on the way up at all- easy to pick lines and power through/ over most everything on the trail. Coming down is fast and fun- some sections are smooth and twisty goodness, while others are just constant rock fields- not too bad, just numb hands :). Beautiful woods and gorgeous trail.

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  • kuala_tahan

    Good trail. First few miles kinda blow, climbing up some scree, loose rocks, stuff to that effect. After those first few miles it turns way better, good singletrack, parts are technical with rock gardens (but not overly technical, all ride-able). Climb the whole way up pretty much, but it's never a real steep climb, all manageable. Fun downhill on the way back, nice singletrack with a bunch of rocks and stuff to make it a little bumpy/tricky.

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  • adam.colba

    I rode this trail from the Sourdough trail head off highway 72 to the reservoir. Out and back I figure it was about 24-25 miles. The first 2 or 3 miles are a bit rocky, but totally manageable. It is deceiving because I felt that the decent back would have been awesome, perhaps my expectations were too high. Don't get me wrong, the downhill at the end was fun, but I've had better experiences on different trails. If you continue past Left Hand Canyon Creek and the paved road, there's an interesting downhill. It's difficult to describe - it's not one full section of rock gardens and techy parts, but various large, round rocks placed all of the trail. It makes it difficult to really pin it and enjoy the decent. After reaching a few trail junctions, the decent smoothed out and was more enjoyable, but I was frightened for the climb out. It turns out that the climb wasn't nearly as bad as anticipated, but I hesitate to say that the decent to the reservoir was worth it. It was a pretty view, but the work to get out...meh. There are better epic rides out there (Kenosha Pass, Buffalo Creek, Monarch Crest, etc). With that said, I would do this trail again. It's always nice to spice up a routine of weekend rides.

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  • Viper45

    I attempted to ride this trail on May 23rd, 2009. About 2.5 miles in the trail was covered in 1' to 3' of snow. I got to Peace Bridge before I was forced to turn around. Since I never got to break through the canopy, I imagine that it would provide nice cover for those looking to get out of the sun on a hot summer day. That said, I can't wait to attempt this trail once we're a little farther into the season. I'm still a novice, but short of a rocky incline every now and again I didn't see anything I couldn't manage. I think the biggest hurdle for most beginners like me is going to be the altitude. * Review edited 5/23/2009

    * Review edited 5/23/2009

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  • keithcath

    This is an out and back route through the trees, starting with a steady climb. There's enough technical interest to take your mind off the fact that it's hard to breathe at this altitude. The downhill payback makes the climb well worth all the puffing - fast and fun.

    * Review edited 10/28/2007

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  • jeeper

    This is an absolutely beautiful trail. It is rocky but the rocks are small and easily ridden. The best part of this trail is no steep or sustained climbs. Amazing considering the altitude. You can ride this anytime of day as you are in dense forest 98% of the time. If you have some energy left when you reach Brainerd Lake Road, I highly recommend the 1 1/2 mile climb up to left hand resovoir. The views up there are spectacular to say the least. A wide well established 4x4 road will guide you there. If you still have some juice left after that you can also ride the final 2 1/2 miles to brainerd lake. But watch out, if the pay station is open they will make you pay $1.

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  • wheelmon

    This is rocky like no other trail, and it also gets lots of use on weekends. It is still fun and challenging on a hardtail, but FS riders will be much happier with it. There are so many better rides closer to civilization that I don't see why this is so popular. But I ride a hardtail. I sure am glad I at least have a Thudbuster seatpost, but I still had to be standing on all the downhills, and I had to be very quick. You will not be relaxing any time on your bike.

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  • jeff82

    Not the greatest trail... Rocky as hell and lots of up. Some good scenery though.

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  • dauw

    Rocky climb first 1.5 miles. Rest is mostly up. Return is mostly down. Just don't bust on a rock or root - it'll hurt. A good view midride.

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  • dirtcoach

    If you like rocks then this is it, nothing real big but big enough if you are not going fast will stop you in a hurry as one of my friends has found out the last time at creek crossing. When climbing the grade is somewhat gentle roller coaster up and down but mostly up, remember there are some ups on the way back but mostly big ring hammer time, ending all to soon. I plan on doing much more of the Indian Peak area rides linked together since this is a rather short ride about 75-90min at a very comfortable pace or when I take a friend along.

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