Distance: 24.4 miles out and back
Elevation gain: 3580 ft
(A Best of the Best ride)
Mt. Diablo is another of the three iconic Bay Area climbs. It’s less tranquil than Mt. Hamilton and less scenic than Mt. Tam, but it’s grand nonetheless. No other ride gives you such a distinct sense of “climbing a mountain.” It’s a long climb but never brutal until the last 100 yards. The view from the top is a tourist attraction, and for good reason—they say on a clear day a person looking north and east can see further than from any other spot on the planet except Kilimanjaro. You can see the mountains around Lake Tahoe.
That being said, it’s not a ride I do for the scenery, though some love it. The foliage is standard East Bay hill shrub and grass, and the vistas, while large, are mostly of East Bay urban sprawl. There are nice wildflower blooms in season.
The ride is approachable from the north, via North Gate Rd., or the south, via South Gate Rd., and they’re both supposed to be good routes—the north route being steeper and shadier—but the south route is the preferred one and it’s the only one I’ve ever done, both ascending and descending. The first half of the descent (from the summit to the Ranger Station) is as good as anything you’ll ever do—if you manage the traffic.
Mt. Diablo, as much as any ride in Bestrides.org, is affected by traffic. Diablo is a magnet for tourists, hikers, mountain bikers, and rock climbers—and their cars. On summer weekends, the place is a zoo. If you were ever going to get up early and be on the bike by 7 am (or call in sick and ride on a weekday), this is the time. In the early morning it’s like the road is closed to cars…and in fact it may well be, since there’s a gate across the road that’s typically closed at night (the park “opens” at 8 am). Riding this ride with no or very few cars triples the pleasure, and changes the descent from good to grand. Despite the crush, the hill is very bike-friendly—there are signs at most blind curves reading “Do not pass bikes on blind curves,” for instance.
There is also the weather to consider. The summit can be foggy, windy, and cold even when the weather at the base is benign. The last time I rode Diablo, it was sunny, still, and 67 degrees at the bottom and 47 degrees, with a blasting wind and freezing white-out fog, at the top. I took more clothes than I thought I’d need, and still froze. This doesn’t mean you shouldn’t ride in such conditions—cold and fog keep the car tourists and hikers away, so on that 47-degree day I never saw a car in my lane during the entire descent.
(To see an interactive version of the map/elevation profile, click on the ride name, upper left, wait for the new map to load, then click on the “full screen” icon, upper right.)
You can get to the bottom of the mountain in many ways. If you drive to the base of the hill, there is a fair amount of grassy shoulder parking along Mt. Diablo Scenic Boulevard, with signs inviting you to use it, but I’d imagine all the spaces would be taken on an ordinary weekend morning. One way is to ride BART to Dublin if you want to get in around 10 miles of mostly flat, quiet grassland riding before starting to climb. Another is to BART to Walnut Creek, ride south on the main street until you can cross under Hwy 680 to Danville Blvd. paralleling 680, and ride Danville Blvd., a popular cycling route on a very pleasant though trafficked residential road with a big bike lane. Go L onto Stone Valley Rd., R on Green Valley Rd., L. on Diablo Rd., and L. onto South Gate Rd. (this road is confusingly signed “Mt. Diablo Scenic Blvd” for its first half mile—don’t let it throw you). This will give you some flats and some mild climbing before you get to the hill. There is traffic all along this route, but there’s good bike lane shoulder all the way to Diablo Rd. Diablo Rd. is narrow with no shoulder, but for the first half of it there’s a nice separated bike path up the left side of the road. After it ends, it’s a short white-knuckle ride with cars whizzing by your shoulder to the turn-off. This leg is marked as a bicycle boulevard (with big white bicycle icons painted in the middle of the lanes), so the cars theoretically know you have a right to be there. I typically park off Danville Blvd. and ride from there, which gives you about 30 minutes of mild climbing for warm-up.
When you start up Mt. Diablo Scenic Blvd, you’ll be sure you’re on the wrong road. You’re riding past schools and houses in what feels like a suburban cul-de-sac. Fear not—all will be well. Right before the first major dip, notice the faded message written on the road the message “Danger severe road damage ahead.” It’s a reminder that there used to be a 1/4 mile stretch of incredibly awful road surface following, but it’s been freshly paved and is now glassy. As you cross it, say a prayer for the intrepid pioneers who came before you.
The climb is actually two climbs, the road up South Gate Rd. to the junction with Summit Rd., and Summit Rd. itself. The first is a fairly easy climb, 4-7%, with lots of variety in the road contour, so you don’t get bored, and a delicious rolling flat through pretty oaks in the middle. Just before that flat you get to the State Park Entrance, a kiosk that takes money from cars. I don’t actually know if bikes are supposed to pay or not (the sign says “ALL vehicles” are supposed to pay), but I’ve never paid and never been asked to. Ten yards past the kiosk on the R is a water fountain. Just before you encounter the kiosk is perhaps the best vista on the entire ride on your R.
At the junction of South Gate Rd. and Summit Rd. there’s the Junction Ranger Station with bathrooms but no water. There’s a photo display identifying the wildflowers you’ve been passing if you’re riding in the spring. Summit Rd. is a one notch steeper than what you’ve just ridden (the numbers deny this, but ask anyone who’s done the ride). A sign says the summit is in 4.5 miles, and it’s dead right. Here you will do some work, but again the road contour is constantly varied so the tough stuff isn’t interminable and you don’t get bored. The final 100 yards are just ridiculously steep (I recorded 16% last time). Every time I do it I say, “You will not walk, damn you—the summit’s right there!”
When you reach the top, take time to gawk at the views and check out the nifty little Visitor Center (you can literally stand on the tippy-top summit of the mountain inside). The very best views aren’t from the parking lot—they’re from the roof of the Visitor Center, which is open to visitors.
When you’re ready to descend, consider the traffic. As i said, the next 4.5 miles back to the Ranger Station is absolutely prime, if the traffic doesn’t spoil it for you. You’ll be going a lot faster than the cars are, so if there are cars in front of you, you’ll be on your brakes and hating it. So I strongly suggest you either 1) watch the cars leaving and wait for a long break—at least 30 seconds, or 2) be up there on a Wednesday or at 9 o’clock in the morning.
The descent down South Gate Rd. is faster, more open, wider, and straighter than the stretch from the summit to the junction, and you may prefer it—depends on what you like. Here you’re slower than the cars (you’re faster than you were on the top stretch, but the cars are faster still), so the problem is reversed, but there is passing room and it’s not a big issue.
Adding miles: You’re a few miles from the Morgan Territory Road ride, though they’re unpleasant miles on a bike. Everything else is a substantial car trip away.
Afterthoughts: If the view from the summit is important to you, you want to wait for clear air. That’s hard to find in the East Bay. Your best bets are a clear day in winter, the day after a storm, or when it’s breezy (which brings its own problems.)
There are frequent bathroom opportunities, since many of the campgrounds lining the road have facilities, and water at the summit as well as the entrance gate.
If you ride Diablo in the late summer or fall, you’ll see lots of male tarantulas wandering the road looking for mates, since it’s tarantula breeding season.