The course
The Chimera runs through the Trabuco District of the Cleveland National Forest in the Santa Ana Mountains, and it ties together steep singletrack like the Holy Jim, Trabuco, and Chiquito trails with long stretches of the Main Divide Truck Trail. It is a figure-eight loop that you cover more than once, and it is almost all unpaved trail and fire road. The 100 miler stacks roughly 20,000 feet or more of climbing, the 100K around 13,000 feet or more, and the high point sits near Santiago Peak on Saddleback Mountain at about 5,689 feet.
The figure eight and the repeated climbs
A lot of mountain hundreds are point-to-point with one or two big climbs you have to survive. The Chimera is not that. It builds its vert out of the same climbs over and over on a figure-eight course you cover multiple times, so the race feels different. There is no single summit waiting for you, just climb after climb on steep singletrack and the Main Divide, and the total gain quietly stacks into the twenty-thousands.
Because you see the same ground more than once, it really pays to know what is coming. Run the first pass of each climb easy, note the landmarks, and save that knowledge for the dark, tired laps later on. This course rewards patience and an even effort way more than it rewards going out hot.
Saddleback, the Main Divide, and the exposure
The high country runs toward Santiago Peak, the tallest point in Orange County at about 5,689 feet, on and around the Main Divide Truck Trail. These ridgeline sections are runnable fire road, which is nice, but they are wide open with no cover. And Southern California in November can still hand you a warm, dry afternoon, sometimes with a Santa Ana wind that pulls the moisture right out of you.
So treat the exposed daytime hours like a heat problem even in late fall. Keep your fluid and sodium up across the open Main Divide stretches, and use the staffed aid stations to cool off and top off. Then respect the other side of it, because once the sun drops in the mountains the temperature can fall hard and those same ridgelines turn cold and windy.
Where the race is won or lost
The climbs are not what get you. The descents are. All that gain comes right back as steep, often technical downhill on tired singletrack, and the people who hammer the early descents shred their quads and pay for it on the later laps, when every drop turns into a grind. Quad-specific downhill training is some of the most race-specific work you can do for this one.
The other thing that decides your race is the long cold night. You will be out in the forest for a full night, climbing and descending in the dark, often alone or with a pacer, after a lot of hours on your feet. Staying warm enough, staying fueled, and staying in it mentally through the low hours is what separates the finishers from the DNFs. Keep moving with some margin against the cutoffs so the night does not catch you behind the clock.
Aid stations and cutoffs
The figure-eight course has a set of staffed aid stations with water, electrolyte fluids, food, and medical aid, plus some more minimal remote stations on the parts of the loop you cannot get crew to. Drop bags and crew are usually allowed at the major checkpoints, but the exact aid locations and crew rules can change with the route, so confirm them for your edition.
The overall time limit has been about 33 hours, with cutoffs at the staffed checkpoints along the way. Pull the official cutoff chart for the edition you are running and build your pacing plan backward from those times, with a buffer. The repeated climbing and the cold night will both slow you down late in the race, so give yourself room.
Pacing strategy for the Chimera 100
A climbing-heavy figure eight with a warm-then-cold profile rewards patience and punishes ego. Pace this race by effort and by grade, not by the flat-ground numbers from your runs back home.
Pace the climbs by grade, not by clock
With roughly 20,000 feet of gain stacked into the same climbs over and over, your moving pace is going to swing all over the place between the steep singletrack and the runnable Main Divide. And that is fine, that is how it should look. Power-hike the steep pitches and run the gentler grades and the descents you can afford to run. Trying to hold a steady minutes-per-mile number across this terrain is a fast way to cook the early climbs and have nothing left for the later laps.
Use our free grade-adjusted pace calculator to turn your flat fitness into honest effort targets for the steep Chimera climbs, so you know whether you are pacing the vert sustainably or burning matches you will want deep into the night.
Protect your quads for the repeated descents
Every foot the Chimera climbs, it gives right back as descent, and on a figure eight you run those descents more than once. Hold back on the early downhills. Run them controlled and light instead of letting gravity hammer your legs, and your back half will be so much better. The people who finish strong here are usually the ones who still have working quads on the final laps.
To set a finish goal that actually accounts for all that vert, use our vert-aware race time calculator. It works the climbing into your projected finish so you are not stuck with a flat-course estimate that the Santa Ana Mountains will quietly tear apart.
Plan for the swing from warm to cold
The Chimera can give you a warm, exposed afternoon on the Main Divide and a genuinely cold, windy night up high, sometimes in the same race. Pace the warm hours like a heat problem, holding your effort down and keeping fluid in. Then count on your pace coming back at night only if you stayed disciplined earlier and stayed warm enough to keep moving.
If you want to see how your fitness from a recent race carries over to a climbing-heavy mountain effort like this, our race equivalent calculator helps you reality-check your goal before you lock in a finish time.
Fueling strategy for the Chimera 100
A long, climbing-heavy effort with a warm-then-cold swing makes fueling and hydration matter as much as fitness. The exposed Main Divide by day and the cold night both kill your appetite, so plan for it.
Carbs: ramp to the high end, on a trained gut
For an effort this long, aim for roughly 60 to 90 grams of carbohydrate per hour, and push toward the high end once your gut is trained for it. Use a glucose-plus-fructose blend so you can take in more than a single sugar lets you, and rehearse your exact hourly carb number on long runs so 80 to 90 g/h feels normal, not like an experiment, by race day.
The conditions make this harder both ways. A hot, dry afternoon on the Main Divide kills your appetite, and so does the cold night. So keep eating through the uncomfortable hours when your stomach wants to quit but your engine still needs the fuel.
Sodium and fluid: built for the exposure
On the exposed ridgelines, especially with a dry Santa Ana wind blowing, you can lose a lot of sweat and fluid, so lean your sodium toward 500 to 700 mg per liter of fluid and carry enough to get through the longer remote stretches between staffed aid. Cramping, a sloshy stomach, and that wrung-out late-race feeling are usually fluid and sodium problems, not fitness problems.
Dial in a plan with our free ultra fueling calculator. Put in your weight, your goal time, and the conditions you expect, and it gives you a carb, sodium, fluid, and caffeine plan per hour built for the Chimera duration. Then go test it in training.
This guide is for planning and training, and it reflects publicly available information about the Chimera 100. Race details, including the date, course, aid stations, cutoffs, and qualifier status, can change year to year, and the Trabuco area has seen wildfire closures. A specific upcoming date could not be confirmed when this was written. Always confirm the current specifics on the official Chimera race site (Old Goat Races) before you train or travel.