OK, ten days ago I had a go at exploring some of these routes. I can't say it was all fun - but it was memorable.
https://connect.garmin.com/modern/ac...bed/3495587514
1. I started in San Dimas Canyon. The trailhead is accessible but barely visible at the dam. its a steep single track and you have to carry or push your bike for most of the of the first 20 minutes.
2. Its then about 9 miles up and along the Sunset Ridge Truck Trail. The first miles are rideable but not spectacular - some views but mostly back down to the IE i had to carry my bike over deep ruts from the last storms The higher up you go the worse it gets and I made very slow progress These south facing sun baked San Gabriel Mountain slopes get really rocky and loose, and added with frequent rockslides, sandy wash and deep ruts and my ride became more of a slow hike and at worst a scramble and not much fun. Even on a MTB I would imagine this would be tough. I decided to push on to the radio towers at Potato Peak and call it a day. Imagine the steepest parts of Mt Lukens but worse.
3. However at the radio towers things change dramatically and for the better. As you tuck around the peak you enter a cooler alpine world with spectacular views down to Baldy Road and Mt Baldy itself. The trail improves enormously as you hug around the mountain on a rolling gradual descent that snakes through empty, wilder and flatter landscape and up over a few shorter climbs. a few loose sections needed a push/hike but all part of the fun.
4. The last section winds down through patchy forest to Glendora Ridge Road passing Sunset Peak. on what is now called the the Sunset Ridge Fire Road I passed a few hikers. Truly spectacular.
Overall about 15.5 miles. I doubt i would ever ride this route again, unless maybe if the first nine miles get graded, but even even then. But I will definitely return to ride starting the opposite direction from GRR up to Potato Peak (is that really the name!). Highly recommended on a gravel bike with some decent tires.
5. From here I headed along GRR for a few miles hoping to loop back down San Dimas Canyon to my car. It was getting late. I had plugged in the return route on my Garmin (famous last words) having studied it on a couple of maps which showed a paved or at least decent fire road.
6. I left GRR at Big Dalton Canyon Rd. You duck under a barrier on to an abandoned paved road heading down to San Dimas Canyon. Soon after the road splits, either taking you down Big Dalton Canyon Road (what you should do) or following on the paved road to the top of West Fork San Dimas Canyon Truck Trail and under a closed gate and back on the dirt (what you shouldn't do.) The dirt road was fine for a mile, but much less trafficked than I imagined, no one had been on here for ages. Another sign I chose to ignore. When it gets late and you are tired I'd probably duck under a flashing neon sign that says "Do not go this way or else."
7. After a mile the dirt road disappears. Well almost disappears - it becomes heavily heavily overgrown. impassible even, but the idea of doubling back up the mountain and finding a long alternate (albeit established) route in the dark to my car, prompted me to stupidly push on in the hope that the trail would clear up. At this point my "trusty" Garmin refused to offer any helpful guidance and mostly froze up. It vaguely showed that I was on the righty trail and headed in the right direction.
8. After 30 mins of bushwacking, either pushing, dragging or carrying my bike I gave up and turned back. I arrived back at GRR in the dark utterly exhausted and very relieved.
9. It was now simply a matter of following GRR to GMR and back down to La Verne and finding my car. but without lights and no moon either. Fortunately GMR was closed to traffic so I had the entire mountain to myself. It was a bizarrely enjoyable even euphoric ride - i have not had to dig that deep for a very long time. Its amazing what you do, if you can just stay positive. At the bottom I was too cold and weary to head back up San Dimas Canyon dam to my car. I found a Starbucks and knocked back coffee and cake until I stopped shaking and called a kind friend to come and pick me up.
Next on my list is...