⏵ Course guide · Bay Area ultra
The Diablo Trail Run climbs straight up Mt. Diablo from Mitchell Canyon Trailhead in Clayton, with the 50K stacking up about 8,000 feet of gain on a mix of single track and dirt road. It is a cupless race with frequent aid, run by Coastal Trail Runs, and it rewards a runner who paces the climb honestly from the gun. I will walk you through the course and cutoffs first, then give you a pacing and fueling plan built for sustained mountain climbing. There are free calculators along the way to dial in your own numbers.
These facts come from the official RunSignup race page. Check the current year details, cutoffs, and aid stations before you commit. Race logistics change year to year.
Every distance starts at Mitchell Canyon Trailhead and climbs into Mt. Diablo State Park, with the longer distances simply covering more of the mountain and stacking up more gain. The 50K runs 38% single track and 60% dirt road, with a sliver of asphalt near the start and finish.
The intermediate cutoffs tell the story of this course: 2 hours 45 minutes to reach mile 9, then 6 hours 35 minutes to reach mile 21. That gap, roughly 12 miles taking almost 4 hours of your budget, is where the bulk of the climbing and the exposure sit. Go out too hard on the early single track and you will feel it on the long dirt-road grinds through the middle of the race.
Coastal Trail Runs keeps this a cupless event to cut down on waste, so there are no pre-filled cups waiting at aid. You need your own bottle, flask, or hydration pack, and the race recommends carrying at least 20 ounces of water between stations, which are spaced every 3 to 5 miles. If you show up without a way to carry fluid, Hydrapak SpeedCups are sold at check-in for about $5, but do not plan on that as your primary system.
Aid stations carry fresh fruit, salty snacks, assorted candy, water, and Skratch electrolyte sports drink, spaced closely enough that you are rarely more than 30 to 45 minutes from a resupply even on the longer 50K. The course itself is marked with ribbon roughly every 200 yards, color coded by distance, so route-finding is not something you need to worry much about once you know your color.
With two intermediate cutoffs on the 50K, mile 9 and mile 21, this is a course where you want to know your split targets before the gun goes off, not figure them out on the fly.
A grade-adjusted pace target for the sustained Mt. Diablo climbs gives you an honest number for effort you can hold across 8,000 feet of gain, rather than a flat-ground pace that falls apart on the mountain. Runners who struggle here almost always ran the early single track too hard and paid for it on the long dirt-road grinds through the middle miles.
The mile 9 and mile 21 intermediate cutoffs are your real pacing checkpoints, not just the overall 9 hour limit. Build a vert-aware finish projection and check it against those splits early, ideally by the first aid station, so you have room to adjust effort while there is still time to do something about it.
⏵ Free tools to pace this course
An 8:00 AM start means you will likely finish the 50K in the afternoon heat if you use much of the 9 hour window. Plan your fueling and hydration around both the cupless format and the warming day.
Aim for roughly 60 to 90 grams of carbohydrate per hour, and use the fresh fruit, salty snacks, and candy at each station to supplement whatever you carry. Because the race is cupless, plan your fluid carrying capacity around the 3 to 5 mile aid spacing and the race's own recommendation of at least 20 ounces of water between stops.
Keep sodium in the 300 to 700 mg per liter range, leaning toward the higher end on the exposed dirt-road sections in the middle and later miles, especially if the day runs warm. Skratch electrolyte drink is available at every aid station, which makes it easy to top off your sodium without carrying a separate mix the whole race.
⏵ Build your fueling plan
Get a carb, sodium, fluid, and caffeine plan per hour built for your weight, your goal time, and a warm Mt. Diablo day with the free ultra fueling calculator. Browse the rest of the free running tools at the tools hub.
⏵ Train for it with Summit Line
Get a race-day plan built around YOUR fitness, this exact Mt. Diablo climbing profile, and your projected splits. Summit Line reads your real training, builds a plan for sustained vert, and rehearses your fueling so race day is something you execute, not guess at.
It is a real climb: the 50K stacks up about 8,000 feet of gain from Mitchell Canyon Trailhead, on a course that is 38% single track and 60% dirt road, with a small stretch of asphalt. Mt. Diablo tops out well above the surrounding East Bay, so the climbing comes in sustained, exposed stretches rather than short punchy rollers. With a 9 hour overall cutoff and intermediate splits to hit at mile 9 and mile 21, it rewards a runner who respects the mountain from the start rather than one who tries to bank time on the early miles.
The 50K climbs about 8,000 feet total, the marathon about 6,760 feet, the half marathon about 3,420 feet, and the 10 miler about 2,420 feet, all on the same Mt. Diablo terrain, just less of it for the shorter distances. The 4 mile option is the outlier at only about 400 feet of gain. Because the longer distances share the same climbing terrain, the extra mileage on the 50K is almost entirely extra vert, not extra flat running.
Coastal Trail Runs (the organizer, sometimes billed as Coastal/Zoom events) runs a cupless race to cut down on waste and litter on the mountain, so there are no pre-filled cups of hydration at the aid stations. You need to bring your own means of carrying fluid, a bottle, flask, or hydration pack, and use it at every stop. The race sells Hydrapak SpeedCups at check-in for around $5 if you show up without one, and you can request a disposable cup from a volunteer in a pinch, but plan to carry your own gear rather than count on that.
With fully stocked aid stations every 3 to 5 miles carrying fresh fruit, salty snacks, assorted candy, water, and Skratch electrolyte sports drink, you have frequent chances to reset your intake. Aim for roughly 60 to 90 grams of carbohydrate per hour, and keep sodium in the 300 to 700 mg per liter range, leaning higher if the day runs warm on the exposed sections of the mountain. Because the race is cupless, carry at least 20 ounces of water between stations as the race itself recommends, and build a per-hour plan rather than relying on aid alone. Dial in your numbers with the free ultra fueling calculator before race day.
The marathon and 50K both carry a 9 hour overall time limit. The marathon has an intermediate cutoff of 3 hours (11:00 AM) at mile 9. The 50K has two intermediate cutoffs: 2 hours 45 minutes (10:45 AM) at mile 9, and 6 hours 35 minutes (2:35 PM) at mile 21. Those splits tell you the race wants steady climbing pace from the start rather than a slow first half made up for later, since falling behind the mile 9 check leaves very little room to recover before the mile 21 check.
It can be, if you respect the vert. The course marking is dense (ribbons roughly every 200 yards, color coded by distance) and the aid stations every 3 to 5 miles mean you are never far from support, which takes a lot of the logistics stress out of a first ultra. The real test is the 8,000 feet of climbing on a 9 hour clock with two intermediate cutoffs to hit. If you have trained on real vert and you pace the early miles conservatively, Diablo gives a well-prepared first-timer a fair shot, but it is not a course to walk into undertrained on hills.
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<a href="https://runsummitline.com/guides/diablo-trail-run">The Diablo Trail Run course guide</a>This guide is independent and for planning only. The course details, dates, cutoffs, and aid stations come from public sources and can change year to year, so confirm the current specifics with the official race before you register or run. The fueling and pacing advice is general and not medical advice.