This site with its great photos and description inspired me to "ride around Arrowrock" dam. The ride is as beautiful as its excellent photos show, but it's a little tougher than described with a lot of 10-11% grades, and my Garmin recorded 15% grades at time. I started from my home in Boise making this slightly over 100 miles in two days verses the 86 miles the site shows. Their GPS download is also great.
Day 1: Wed 20 May 2026
Boise to Long Gulch Summit about 4 miles from the Y Stop
53.7 miles, 6:57 riding time, 5,417 ft elevation gain
The GPS download starts at Diversion Dam (12.9 miles from my home), so I reset my manual odometer there to match my cue sheet's distances while letting my Garmin record the entire ride although at Lucky Peak Dam it was reading "ready to navigate". I restarted the course and had no further issues with it on either day. Lydle Gulch is steep (my Garmin recorded a max of 14.7% followed by a short steep section with lots of loose rocks which I ended up pushing through.
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| looking back on the entry to Lydle Gulch, the real beginning of this ride |
For a short way just past Point Bonneville the trail nearly disappears becoming little more than bent grass from a vehicle or two driving over it, but soon it merges onto E Blacks Creek Rd- for just over 3 miles it becomes some of the smoothest pavement I've been on in years (with no traffic) but then becomes fairly smooth hard-pan.
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| smooth hard-pan rides well |
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| Reaching some timber |
The first climb up to Blacks Creek Summit is moderate but with a 10% grade just before the top where I consumed my lunch, PB&J. Then it's 7 miles of downhill before the next short climb which has a climb of 10% grade before reaching the first overlook of the S Fork.
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| our route down to the South Fork of the Boise River |
It's a fun but short downhill before riding along a bench not far about the river, crossing a bridge and starting back up a moderate climb that becomes steeper reaching 11% according to the backpacking site, but I see my Garmin recorded a brief stint at 18.5% grade.
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| Looking back at the descent to the South Fork |
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| View from the bench along the South Fork with the route in the distance |
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| Steve riding on the bench above the S Fork- photo by Mark |
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| Steve starting the climb out of the S Fork- photo by Mark |
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| the climb out of the S Fork |
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| Riding along a bench above the S Fork |
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| The Y Stop looks clean and like a good place to eat if you arrive during their limited and changing operating hours |
It's not far from the top to the Y Stop which was closed and which has very limited and changing hours, so call them before-hand if you want to eat there (208-598-4998). If they're opened the evening you ride it's an easy 4 mile ride on out to Long Gulch. I was getting tired, so I told Mark I'd like to camp about 5:00 at the Long Gulch Summit. It has no pic-nic tables, no water, nor pit-toilet, but it offers green grass and a flat spots to set up tents. Mark had fixed a great dinner of a hearty chicken and black bean soup or stew and home-made bread.
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| the road out to Long Gulch dispersed camping |
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| our campsite at Long Gulch- we were too tired to stay up until after dark for a better campfire photo |
Day 2: Thur 21 May 2026
Long Gulch Summit to Boise, Idaho
60.7 miles, 7:21 riding time, 3,517 ft of elevation gain
I was cold in my tent and sleeping bag and the morning temp was only 30°, so I went for a short walk hoping to warm up while Mark was sleeping in his pickup. He fixed a hearty breakfast which we ate in the pickup with the heater and seat warmers going, and then he headed home. The next 6 miles were mostly downhill followed by about 4 miles of moderate climbing with a short section of 8%, then it was downhill to the Middle Fork of the Boise River.
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| starting up the first hill after the initial down hill |
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| The road down to the South Fork of the Boise River |
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| looking back across the S Fork toward Prairie |
When I reached the Willow Creek Campground, I had lunch at their pic-nic tables and checked it out. It was nearly full, but the pit toilet was acceptable and the pic-nic tables would have been great for camping. However, I'd recommend camping at Long Gulch Summit so you still have more of a feeling of adventure ahead of you.
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| Wilson Creek Campgound was nearly full but had a pit toilet, pic-nic table and sometimes potable water |
From here the road starts to be more heavily trafficked with many potholes and lots of washboards (unlike the rest of the route). Down a little lower the free flowing Middle Fork becomes the Arrowrock Reservoir, and for me the sense of adventure ended.
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| The South Fork become Arrowrock Reservoir |
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| There's still some great scenery along the Arrowrock Reservoir |
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| Arrowrock Dam |
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| my chosen stead for this adventure |
Just below Arrowrock Dam the washboarded road yields to pavement! Then there's the climb up Hwy 21 and the turn off onto Highland Valley Rd which leads to the archery range. There it became a trail until 2024 when the area burnt and the old road bed which had long ago degenerated to a trail with some single track and some double track was made a then current fire road. It's still a steep descent but all the "technical" and single track is gone, and there's rarely any grass in the middle now. After riding that, I rode up to the official starting point and back home.
This was a great adventure with a lot of beautiful country, but it is harder than that website would indicate. Mark's carrying my sleeping gear and food made it a lot more enjoyable for me.
Happy cycling for fun, fitness, and transportation!
Steve
