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
  • 1 rides
  • 10 miles average
6 Months
  • 1 rides
  • 10 miles avg distance
All
  • 50 rides
  • Last: Aug 16, 2026
c1c2c3c4
January
February
March
April
May
June
July
August
September
October
November
December
update trails status or condition

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

view (622)
close
  • Basemap  Map 
    • Pro
    • Pro
    • Pro
    • Pro
    • Pro
    • Pro
3D
Trail Conditions
  • Unknown
  • Snow Groomed
  • Snow Packed
  • Snow Covered
  • Snow Cover Partial
  • Freeze/thaw Cycle
  • Icy
  • Prevalent Mud
  • Wet
  • Variable
  • Ideal
  • Dry
  • Very Dry
Trail Flow (Ridden Direction)
Trailforks scans users activity logs to determine the most popular direction each trail is ridden. A good flowing trail network will have most trails flowing in a single direction according to their intension.
The colour categories are based on what percentage of users are riding a trail in its intended direction.
  • > 96%
  • > 90%
  • > 80%
  • > 70%
  • > 50%
  • < 50%
  • bi-directional trail
  • no data
Trail Last Ridden
Trailforks scans activity logs to determine the last time a trail was ridden.
  • < 2 days
  • < 1 week
  • < 2 weeks
  • < 1 month
  • < 6 months
  • > 6 months
Trail Ridden Direction
The intended direction a trail should be ridden.
  • Downhill Only
  • Downhill Primary
  • Both Directions
  • Uphill Primary
  • Uphill Only
  • One Direction
Contribute Details
Colors indicate trail is missing specified detail.
  • Description
  • Photos
  • Description & Photos
  • Videos
Trail Popularity ?
Trailforks scans activity logs to determine which trails are ridden the most in the last 9 months. Trails are compared with nearby trails in the same city region with a possible 25 colour shades. Think of this as a heatmap, more activities = more kinetic energy = warmer colors.
  • most popular
  • popular
  • less popular
  • not popular
ATV/ORV/OHV Filter
Max Vehicle Width
inches
US Cell Coverage
Legend
cell carrier legend

Radar Time
Activity Recordings
Trailforks uses anonymized public activity data. ?
Activity Recordings
Trailforks uses anonymized public activity data. ?
Winter Trails
Warning A routing network for winter maps does not exist. Selecting trails using the winter trails layer has been disabled.
Missing Trails
Most Popular
Least Popular
Trails are colored based on popularity. The more popular a trail is, the more red. Less popular trails trend towards green.
Jump Magnitude Heatmap
Heatmap of where users jump on trails. Zoom in to see individual jumps, click circles to view jump details.
BC Backroad Status

Service Road Atlas is a free to use, community-driven service for viewing and creating reports on the numerous back-country service roads around B.C. and Alberta.

map legend
Slope Aspect
Direction the slope faces
Flat N NE E SE S SW W NW
Trails Deemphasized
Trails are shown in grey.
disable
Only show trails with no bike usage.
Enable
Suggested Layers
Based on selected activity type

    Save the current map location and zoom level as your default home location whenever this page is loaded.

    Save
        Directions to lower-clamshell trailhead (34.170500, -117.995410)
        View on Discover Map

        Photos

        27 more »
        mtb
        184 |
        Jan 22, 2023 @ 4:52pm
        Jan 22, 2023
        mtb
        158 |
        Jan 22, 2023 @ 4:50pm
        Jan 22, 2023
        mtb
        187 |
        May 22, 2022 @ 2:55pm
        May 22, 2022
        mtb
        186 |
        May 22, 2022 @ 2:55pm
        May 22, 2022

        Videos

        no videos have been added for Lower Clamshell yet, add a video.

        Links

        4.0 ★★★★★
        2 Ratings
        5 ★ 50%
        4 ★
        3 ★ 50%
        2 ★
        1 ★

        4 Reviews & Comments


        We hope you've been enjoying Trailforks!

        Create a FREE account to view trail comments and much more.

        Create a Free Account

        Nearby Trails

        Monrovia

        • By derkderkallTF Pro & contributors
        • #177129 - 7,180 views

        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.
        ▼ How long is Lower Clamshell?
        Lower Clamshell is 3.6 miles long. The trail type is singletrack.
        ▼ Are dogs allowed on Lower Clamshell?
        Yes, dogs are allowed on Lower Clamshell. Please keep dogs on a leash where required and clean up after them.
        ▼ When is the best time of year to ride Lower Clamshell?
        Based on activity log data, the most popular months to ride Lower Clamshell are:
        • July (11 activities)
        • June (6 activities)
        • January (5 activities)
        Check the reports page for current trail conditions.
        ▼ How do I access Lower Clamshell? Where is the closest parking trailhead?
        The closest parking and trailhead locations to Lower Clamshell are: View all parking locations in the area.
        ▼ How long does it take to ride Lower Clamshell?
        Based on recorded activities, it takes an average of 41 minutes to ride Lower Clamshell. The trail is 3.6 miles long. Actual times will vary based on fitness level, conditions, and pace. View recent activity logs for more details.
        ▼ How busy is Lower Clamshell?
        Lower Clamshell is a very popular trail. There have been 616 recorded activities on this trail. The trail has received 618 check-ins. View recent activity on this trail.

        Hit the Trail

        Open in App

        Get this trail on your phone instantly.
        open trail in app

        Download Trail

        Save to wishlist, Garmin & download.
        save the trail

        Find Related Routes

        Find routes and users activities that include this trail.
        find routes for this trail

        You must enter a description before submitting.