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Brazen Racing Diablo Trails Challenge 50k



31.4 mile 50.5 kilometer loop
83% Runnable


Ascent: 6,147' 1,873 m
Descent: -6,148' -1,874 m
High: 3,806' 1,160 m
Low: 368' 112 m


Avg Grade: 7% (4°)
Max Grade: 35% (19°)


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Trail shared by Lia Maria

A challenging but beautiful tour of East Bay Hills, conquering both the Summit and North Peak of Mt. Diablo.

Lia Maria

Features River/Creek · Spring · Views · Wildflowers

Part of the course (around miles 11-13.5) is on private property and is not open to training outside of the race.


Brazen Racing's Diablo Trails Challenge Races (50k, half marathon, 10k, and 5k) have earned a reputation of being challenging but worthwhile and beautiful races.

This 50k loop course winds its way through the East Bay Hills, arcing over and around hilltops and through tree-sheltered canyons before climbing to Mt. Diablo's summit. From there, expect a short descent before another climb/scramble to the top of the North Peak, after which the runners make their way back through the hills to the race start/finish area at Castle Rock Park.


The trail begins at Castle Rock Park. It starts off with a rolling ascent up into more of the hills, meandering over them as it makes its way to Mt. Diablo. As the trail progresses, it crosses through some wooded canyon areas as well, often skirting the canyon side.

Around mile 13, there is a short out-and-back along a dirt road before heading out on the trail again. Midway through the course is a climb to Mt. Diablo's summit, which becomes a bit of a steeper run near the end. From the summit of Mt. Diablo, you can see for 200 miles in good conditions. San Francisco and the Sierras can be visible, as well as a wide swath of additional landscape.

After reaching the summit around mile 19 or 20, the trail descends back down, around, and up to the North Peak. The last part of the trail to the North Peak is steeper and a little tricky - exercise caution. It can even be a bit of a scramble up (though there is a path).

After coming down from the North Peak, the trail winds its way around the other side of the mountain. From here, the trail covers more canyons, ups and downs through the hills before cresting a ridge again. It takes a course over open hills until it descends back to a more wooded area near the finish. Here, there are a number of stream crossings before reaching the start/finish area at Castle Rock Park again.

(Note: percentage of singletrack is a rough estimate)

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18 Views Last Month
374 Since Feb 21, 2017



Summit Trail
Oct 22, 2017 near Blackhawk, CA
Wall Point
Oct 22, 2017 near Diablo, CA
Stage Road/Trail
Oct 22, 2017 near Diablo, CA
Diablo Summit observation deck lookout
Oct 22, 2017 near Blackhawk, CA
Summit Trail
Oct 22, 2017 near Blackhawk, CA
Burma Road through Pine Canyon in the spring
Jan 5, 2018 near Diablo, CA


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