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Lucas Valley Loop

 3.6 (26)

A scenic and fun loop that incorporates two of the few singletrack trails in Marin, not Tamarancho.

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1,842' 562 m


149' 45 m


2,977' 907 m


2,975' 907 m



Avg Grade (4°)


Max Grade (13°)

Dogs Off-leash

E-Bikes Unknown


Outside of China Camp State Park and Tamarancho, there are not a lot of bike-legal singletrack trails in Marin, but this loop manages to catch two of them. The main downside to this loop is the start - going up a very steep (over 20% grade) fireroad for the first mile or so. But, once you get to the top, the views are great, the ride down Big Rock Trail is very fun, then another climb, then going in the fun direction on 680 Trail, and then some fun cruiser downhill fireroad to the car. So it's a good 15-mile loop with over 3,000 feet of climbing.

Need to Know

  • Navigating can be a bit tricky, especially near the starts. Pay attention to the directions and keep the MTB Project mobile app handy.
  • To lessen the difficulty of climbing on this loop, it's possible to ride it in reverse (riders can even start at the base of the Sunrise Fire Road). This does mean using the singletrack trails for climbing instead of descending, but it's a good option if you're looking to save some marks on the grunt scale.


The parking spot is on the south side of Lucas Valley road, about 2 miles west of the 101.

The first part of the ride is on blacktop and gets you to the base of the very steep fire road. Here are the instructions:

1) Follow Lucas Valley Road west for a mile.
2) Take right onto Bridgegate Dr.
3) Take 2nd left onto Creekside.
4) About .4 miles take right up Luiz Fire Road.

Luiz Fire Road is, by far, the least fun and least pleasant part of this ride. It's only a mile, but a lot of the road is over 20% grade. But as you walk up (I'm not strong enough to ride this trail), enjoy the view as you slowly ascend. Once you get to the top, you are on Big Rock Ridge.

At the top, take the left onto Big Rock Ridge Fire Road and head west. This fire road has great views both north and south, as well as to the East, and has a lot of up and downs, but slowly ascends until you reach the cell phone towers that are at the top and at an elevation of 1,725 feet. This is a great spot to enjoy the view as you can nearly see 360 degrees. On a clear day, you can see San Francisco, Mt. Diablo, and the edge of Tomales Bay.

Now comes the best part of this ride - going down Big Rock Trail . Big Rock Trail is one of the few bike legal singletrack trails in Marin and is a very fun descent. Nice flow, nice views, and not too many people. There are a few blind turns, so watch the speed. One fun part of this ride is that you are looking down on Sky Ranch, where they made a few Star Wars movies.

Once at the bottom, cross the street and you now have a pretty mellow fire road ascent up Loma Alta Fire Road. Compared to Luiz Fire Road, this fire road is rather pleasant and if you like cows, you should enjoy this section. A little past halfway up is an alternative portion of Loma Alta Fire Road that follows the contours a bit better and doesn't reach the summit of Loma Alta hill ( 1592 feet). Given that it's only saving you a few hundred feet, and given that the view at the top is a nice 360-degree view, keep going straight and enjoy the view.

Once at the top, this is the time to take a break, enjoy the view and get ready for some fun. Go down and take the left on onto 680 Trail. This trail was built in 2012 and although it is a bike legal multi-use trail, the Marin mountain bike community wasn't particularly happy with it as the Marin Open Space Department smoothed it out to the point where it is more like a sidewalk than a mountain trail.

As a result, more experienced riders find it a bit boring, but it is fun and a great ride for beginner or intermediate mountain bikers. The beginning section traverses some open meadows and when the poppies are blooming in the spring, there is a section about a third of the way in that is amazing. There is a bit of fire road in the middle that has some big erosion control bumps that one could have some fun on. The trail then goes into some woods and winds through manzanita and California oaks. Personally, I like this section of the trail the best, but again, they smoothed it out a bit too much.

Once you get to the end of 680 Trail, you are back on fire roads and have a fun descent to the car, but be careful as it's easy to end up on the wrong side of this ridge. So take right on Luiz Ranch Fire Road for about a third of a mile and take the first left onto Terra Linda Ridge Fire Road. This left is easy to miss and going straight will put you on the wrong side of the ridge!

Stay left at next intersection and you'll be down at your car in a bit.

History & Background

680 Trail and Big Rock Trail are two of the 'newer' bike legal multi-use trails in Marin. This loop incorporates both and is a reminder that mountain bikers really want to see construction of more narrow multi-use trails.


Local Club: Access4Bikes (A4B)

Land Manager: Marin County Parks

Shared By:

Jackson Ratcliffe

Trail Ratings

  3.6 from 26 votes


in Marin County


  3.6 from 26 votes
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41 Views Last Month
13,144 Since Sep 20, 2015



View back down the trail from the top.
Jun 1, 2014 near Sleepy…, CA
View looking north at Big Rock Ridge and the cell phone towers. The nasty fire road is on the right.
Oct 18, 2015 near Sleepy…, CA
View from top of Loma Alta, looking south towards San Francisco.
Oct 18, 2015 near Sleepy…, CA
View from Big Rock Ridge looking East at Mt Diablo in the distance
Oct 18, 2015 near Lucas V…, CA
Tam from the Loma Alta Fire Road.
May 8, 2017 near Sleepy…, CA
The fun and flowy part near the bottom.
Oct 18, 2015 near Lucas V…, CA


Current Trail Conditions

All Clear 67 days ago
Add Your Check-In


Jun 24, 2023
Laz Haces
5h 29m
Jan 10, 2023
Eddy Ledezma
May 2, 2022
Greg Walker 2
Rode up Queenstone FR instead of Luiz. Still a steep climb! Marin fire roads are no joke. Big Rock and 608 are both really fun singletrack sections. 17mi
Feb 13, 2022
Armando Enriquez
Jan 30, 2022
James Bishop
Add Ponti Ridge, Lower Porcupine, and Upper Porcupine for all the best trails in the area that aren't Tam. Remember Marin fire roads are STEEP! 34mi
Jan 16, 2022
Scott Preckwinkle
Oct 14, 2021
Tony Tobia
Sep 14, 2021
Natan Liberman