Marin Mountains III 200K
part of the SFR Adventure Series
UPDATE: in 2025 the San Francisco Randonneurs are running the Marin Mountains 200K on April 26. Register here.
The Marin Mountains 200K has always been the most technical of the SFR Adventure Series rides—more of a real mountain bike ride than merely a hilly ride with a few gravel stretches.
From 2012 through 2024, with the exception of 2019, the course featured a big loop that included dirt segments on Mount Tam, Pine Mountain, Mount Vision, and Bolinas Ridge. You can read more about it here and see the map here. In 2019, due to storm damage on Mount Vision, the ride featured an out-and-back to Limantour Beach. This variant, which we dubbed “Marin Mountains II”, was never repeated.
In 2025, however, permitting issues at Point Reyes National Seashore have forced us to rethink major parts of the course, avoiding all sections west of Highway 1.
The result is a formidable new challenge, “Marin Mountains III” (map). The original course featured approximately 3600 m of climbing and 38 km of dirt (19% of the course). Marin Mountains III adds about 300 m of climbing, but most importantly it comprises a whopping 67 km (33%) of dirt, including several segments that are technical or in poor condition.
Timing
Given the course’s difficulty, the event is classified as a RUSA gravel brevet, not an ACP event. This change allows us to extend the time limit by one minute per kilometer of dirt, from 13h30m to 14h37m.
Equipment recommendations
The ideal rig for this ride is a gravel or monstercross bike with slick or moderately knobby tires in the range of 38-42 mm.
A road bike with 32 or even 34 mm tires would be tough going on some of the new dirt sections. But a suspension MTB remains overkill even for this new edition: it will help you on the dirt but slow you down on the paved sections.
Make sure your tires are not too supple, or you risk sidewall cuts.
Course details
Where the old course featured two pairs of big climbs with dirt segments (the striped sections) …
… Marin Mountains III features, fittingly enough, two sets of three big climbs with dirt segments:
MM III omits Mount Vision and the Point Reyes peninsula, but it adds several new dirt challenges:
- km 42: an exploration of the Mount Tam backcountry around Five Corners. The trails are in excellent condition, but control your speed and look out for hikers and runners. You may want to detour to Sky Oaks ranger station to refill your bottles.
- km 62: Loma Alta between Fairfax and Lucas Valley Road. A 4 km gravel climb with an average grade of 9.5%, followed by a bumpy descent to Lucas Valley. (This is a mixed-use trail, and the descent has a lot of hardened hoof prints during the dry season.)
- km 164: Coast View Trail from Pantoll to Muir Beach. The panorama here on a clear day is hard to beat, but keep your eyes on the trail as well: there are roots, rocks, and some very deep ruts that require good technique.
- km 175: Miwok and Coastal Trails from Highway 1 to Tennessee Valley. The paved climb from Muir Beach to the trailhead comprises only half of the ascent. The dirt trail begins gently, but the summit section may require dismounting. Be careful on the beautiful, swooping descent to Tennessee Valley.
- km 183: Marincello and Bobcat Trails from Tennessee Valley to Rodeo Valley. The dirt here is in excellent condition, but by this point your legs may not be.
The ride passes through the Bunker Road Tunnel on its way to the Golden Gate Bridge. Enjoy the cool air and the smooth pavement, you’re almost home!