Mundane First: About the Routes
The intermediate and advanced start at the lake and climb BBR (Burdick - Butters), go down Redwood Road, over lower Pinehurst, then over Canyon to Moraga and down St. Mary's Road and eventually to the southern base of Diablo. That route to Moraga is a good one to know -- it's a good start to many rides. I personally wouldn't do that much climbing before climbing Mt. Diablo, but for the stronger riders it's a good warm up.
The Humanes start from Lafayette BART and the official route climbs to the junction ranger station at about 2200 feet or so. Rest your legs and get some water and decide whether you want to do the official OYJ route and continue down the north side .... or, join those who do the last 4 1/2 miles and 1700 feet or so to the top.
Light riders don't do Mt. Diablo but instead do a pleasant, circuitous, not quite flat, tour of the Diablo Valley from Orinda BART to Moraga, skirting Lafayette and Walnut Creek, through Danville, San Ramon, and to the Dublin/Pleasanton BART.
You know you're climbing a mountain you climb around a wide curve and you look at the road sloping endlessly upward around the next curve, which is maybe the better part of a mile away and a couple of hundred feet above where you are now. Cyclists at this distance looking like multi-color ants slowly rounding that faraway shoulder ... The views out over the valleys below slowly becoming aerial and expansive.
Mt. Hamilton is a longer climb and ultimately more elevation, and Mt. Tamalpais is steeper but smaller. But I think, all things considered, Mt. Diablo is the biggest single climb on our route sheets. It tends to get steeper and hotter each mile going up.
I have heard that strong cyclists, in training for major rides in the Sierras, will go up and down Mt. Diablo three times in a day. For most of us, though, Mt. Diablo once is pretty much enough for the day, thank you.
Diablo is a doable ride. I did it for the first time in my second season, and I was already about 60 years old, overweight and not in what you would call excellent cycling shape. If I can do it, you can—IF you've been getting out and riding and climbing. If you don't feel up to it, there's no harm in stopping at the ranger station. Going to the top can be a goal for the future.
And ... whether your goal is the ranger station or the top, especially if it's your first time, you will know you have accomplished something significant. The views going up and from the top are astonishing. If it's a clear day, you can see forever, as the song says. People will hang out at the ranger station and at the top and chat and enjoy the time.
Things you should know:
Oh yes ... the heat.
- Everyone who's climbed Diablo on a hot day will tell you that it gets its name from being as hot as Hell. If it's 85 degrees in the valley below, it'll be 100 or more on Diablo. It's an appropriately evil twist of the local weather rule that it should get cooler as you ascend. Bring plenty of water and electrolytes if it's warm.
- There's water at the south gate entrance to the park. There's water, restrooms, benches, shade and cyclists resting at the junction ranger station. There's no water that I know of between the ranger station and the top.
- At the top, there is shade, water, neat clean rest rooms, a museum and neat photographs, a fountain, and greetings from everyone who made it there before you.
- The climb to the top is harder than the climb to the ranger station. It's steeper and oh, by the way, did I mention that on some days it can get very hot?
When you're almost to the top, beware the last 200 or so feet. It's an ~ 18% grade, which is technical way of saying it's awfully steep. It's no shame to walk it if you need to. I always pedal it if I can, however, partly because I hate giving up on the last 200 feet but mostly because I doubt I would make it up if I have to walk it. :}
The descent: careful, watch for cyclists and cars come up the narrow road, and for rocks and gravel next to the hill side of the road. Careful especially going down the north side toward Pleasant Hill—the descent requires your attention—some of the turns are sharp and narrow, and the road sometimes slopes the wrong way.