more stats
3.6 miles
Distance
701 ft
Climb
-1,100 ft
Descent
00:34:48
Avg time
-400 ft
Altitude change
756 ft
Altitude min
1,588 ft
Altitude max
1,156 ft
Altitude start
755 ft
Altitude end
-2.1%
Grade
-67.1%
Grade max
42.7%
Grade min
1 mile
Distance climb
2 miles
Distance down
2,192 ft
Distance flat
00:34:48
Avg time

Lower Clamshell Details

  • Activities
    • Mountain Bike
    • Hike
    • Trail Running
  • Riding Area
    Monrovia
    California
  • Difficulty Rating
    Blue Rate
  • Local Popularity
    100 in Mountain Biking [+]
    • 5 in Trail Running
    • 100 in Hiking
  • Global Ranking
    #52155 in Mountain Biking [+]
    • #226130 in Trail Running
    • #568 in Hiking
  • Trail Type
    Singletrack
  • Bike Type
    XC
  • Direction
    Both Directions
    Popular Direction Shown
  • Dogs Allowed
    Yes
  • Land Owner
    City of Monvrovia

Mostly fire road through the Monovia Hillside Wilderness Preserve. However, there are a couple sections (1 optional) where beginners might it too challenging. Going counterclockwise and starting near the Canyon Park, follow the signs for the trail. While it may look like there is a network of options, many cross private land with no access. Once you reach the summit, the trail turns into a short singletrack section and goes down numerous steep and tight switchbacks, that will test your skill. At the bottom, the fireroad resumes. Follow it and the signs until you see a sign on the right that says advanced trail. You can bypass this and continue on the fireroad, or take the fork to the right for a more challenging experience. The advanced section takes you up a short climb and then heads down. Eventually you will come to a hillside with more tight switchbacks and some mild exposure. At the bottom continue and it reconnects with the fire road for a short distance until you reach the gate.

Local Trail Association
Traditionally Indigenous Territory

Recent Activity on Trail

Past Week
  • 0 rides
  •  
6 Months
  • 2 rides
  • 9 miles avg distance
All
  • 49 rides
  • Last: Jun 17, 2026
c1c2c3c4
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Lower Clamshell Trail Reports

statusdatedescription
Dec 28, 2025 @ 9:17am (America/Los_Angeles)
Dec 28, 2025
 Lots of damage in the form of ruts and part of the tread washed out on the switchbacks. Minor ruts from the bench and on the fast fire break....
Apr 12, 2025 @ 4:30pm
Apr 12, 2025
 First ride on this loop. Switchbacks below Sunset Bench are in really good condition. Recent grooming is evident.
Feb 27, 2025 @ 1:36pm
Feb 27, 2025
 There was a fire line bulldozed from the sunset bench, down the switchbacks, along the ridge and down the firebreak to the turnoff towards Arcadia...
Jan 4, 2025 @ 10:28am
Jan 4, 2025
 No major changes in trail status. Good condition, not overgrown but a little loose, dry and rutted on the switchbacks
Jun 1, 2024 @ 11:03pm
Jun 1, 2024
 Good to go Switchbacks have been trimmed
more »
Status:
on Dec 28, 2025
Variable
Avg: 4.13 (2 votes)
Your vote: 0

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        Directions to lower-clamshell trailhead (34.170500, -117.995410)

        Photos

        27 more »
        181 |
        Jan 22, 2023 @ 4:52pm
        Jan 22, 2023
        150 |
        Jan 22, 2023 @ 4:50pm
        Jan 22, 2023
        182 |
        May 22, 2022 @ 2:55pm
        May 22, 2022
        166 |
        May 22, 2022 @ 2:55pm
        May 22, 2022

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        4 Reviews & Comments


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        Frequently Asked Questions About Lower Clamshell

        ▼ Where is Lower Clamshell located?
        Lower Clamshell is located in Monrovia, California, United States. It is part of the Monrovia trail network. The trailhead is located at coordinates 34.1705, -117.99541.
        ▼ How hard is Lower Clamshell?
        Lower Clamshell is rated as Blue difficulty. The average grade is 2.1%.
        ▼ What is the elevation gain for Lower Clamshell?
        Lower Clamshell has 701 ft of elevation gain. The trail has 1,100 ft of elevation descent. The elevation ranges from 756 ft to 1,588 ft.
        ▼ Is Lower Clamshell a point to point trail?
        Lower Clamshell is not a point to point trail. The direction is Both Directions. The trail type is singletrack.

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