This route takes you from deep in the Santa Cruz mountains across the coastal range, over the Dumbarton Bridge, and up the Bay Trail on the east bay shore to the far northwest corner of Alameda county. Here's a map of the route
The first climb on Mountain Charlie Road is a gem. Very little traffic, shaded, good grade with the exception of 3 steepish ramps, decent pavement for climbing, and quiet. There's tons of recovery sections, and even some downhill. I'd hold back a bit doing this downhill though, a bit bumpy and there's some loose gravel/sand washed across a few curves on the lower sections. Charles "Mountain Charlie" McKiernan's road is one of the original roads from Scotts Valley over to San Jose, and you can feel it in the way the road runs along the contours to avoid steep grades and includes some downhills. In contrast highway 17, the nearby modern route, is just about all uphill to Patchen pass.
The section up Summit Road/Highway 35 after Mountain Charlie is shaded for the most part, with a few downhills in the mix. The road bears right after Bear Creek Road goes off to the left down to Boulder Creek, and it gets secluded and quite sylvan.
The pavement is very smooth after Black Road intersects from the right. Just in time too, because there's more exposed sections in the early afternoon and it's nice to be rolling efficiently on the intermittent uphills. After the parking lot for Castle Rock park (fun climbing area) it's downhill to Saratoga Gap, where we cross Highway 9.
The road continues rolling up and down along the ridge-line for the next 6 miles to the Page Mill road turnoff. There's water on the right about 1 mile down Page Mill, the fountain is next to a black metal gate on a short driveway on the south side.
The Page Mill downhill is excellent, although it pays to be cautious in the upper section where it gets quite steep in a few places. There's a tricky right-hand hairpin right across from a gate on your left (open space access #3). After the road flattens a left on Arastredero Road leads to another open space on an exposed incline section. Right on Alpine and down to Sand Hill Road. The path/sidewalk on the right is shaded, but it's not good pavement.
Sand Hill Road has a decent bike lane all the way to El Camino Real, cross and continue straight to Willow Avenue via a bike bridge. The ride over the Dumbarton bridge is windy as always. I stay in the middle of the bike lane dodging occasional windblown empty plastic bottles.
I crossed over the freeway on the bike/pedestrian bridge towards Coyote Hills open space but didn't see an obvious way to drop back to Old Quarry Road and ended up scrambling down on the east side of the bridge abutment. Obviously not the first person to do this. It's sketchy in bike cleats. The map above shows the longer route on the road, following Marshlands Road SE to Thornton N, but on a windy day it was nice to cut out that bit. Once you turn left at Ardenwood the roads are fairly wide and smooth for several miles. Most days you'll be riding into or across a stiff wind on this northward leg by early afternoon.
I picked up the Bay Trail off of Cabot Road in Union City/San Leandro. It's paved for about 1/3 mile, then turns to gravel and hard-packed dirt. The scenery is wonderful with the bay shore about five or ten yards to the left and lagoons, marshes, and grasslands on the right. I see numerous black-necked stilts probing for dinner in the shallows, and get to see a Forster's or Caspian tern up close as it matches my pace for about five seconds ten feet to my right at eye level.
Riding on 23 mm tires but there's no issues with the trail, the bike will need a good cleaning though. The trail gets a bit hard to follow after an access point parking area near the end of Grant Avenue. The widest trail heads due north across a flat before veering slightly right (east) to run parallel to the tidal inlet. It joins a paved trail after about 1/2 mile, near Lewelling Boulevard (named after Henderson Lewelling the abolitionist, horticulturist, and grandfather of the west coast fruit industry), just before a bridge. It's smooth pavement again, with a wide gravel shoulder to the right coming in handy when the trail gets congested.
Neptune Drive ends at Oyster Bay park, where we take the dirt trail to the Bill Lockyer bridge (sponsor of SB100-1987 that established the Bay Trail). The trail winds past a golf course and through the Oakland Airport and across Bay Farm island. The bike route on the sidewalk on the west side of Harbor Bay Parkway could be a good tip on a windy day as the thick hedge may provide some shelter, but I stayed on the wide boulevard. Continue due north on the bike trail after crossing Doolittle Drive (named for Alameda native son Jimmy Doolittle who led a B-25 squadron on a daring one-way air raid on Tokyo early in WWII. That raid was launched from the USS Hornet, the same ship which later retrieved the Apollo 11 astronauts after their splashdown, and that ship is now a floating museum on the Alameda estuary).
The bike lane on Fernside is very wide and I realize how relaxing it has been to be mostly off-street or on good bike lanes all afternoon. I take the sidewalk on the Fruitvale bridge, then wind along the Oakland estuary shore on rough and rutted Embarcadero Drive. Through Jack London Square area on 2nd. Too bad Blue Bottle coffee was closed, a shot of espresso would have been most welcome at the time.
After reviewing my actual route I think better routing would be on Mandela Parkway, where there's a bike lane. I was getting tired at this point and took MLK up to 14th instead. Not a recommended alternative, but functional. Then took 14th to Wood to Beach to Horton because I knew the roads, but Wood has a lot of railroad track to deal with on the right side of the street. Mandela is probably the better call, will have to try it out.
Back on a bike trail through Berkeley Aquatic Park and over the bridge, then along the Bay Trail again along Eastshore State Park and through the backside of Golden Gate Fields to the Buchanan street bike/pedestrian bridge in Albany and our ending point at El Cerrito Plaza BART station.
What a great adventure. Mountain Charlie is a keeper, the section from Scotts Valley to Saratoga Gap has to be on my top 5 list of Bay Area rides. The Bay Trail along the east bay shore is also something special, even though it's flat it's got great potential to extend my riding into new areas. I am imagining a loop down Grizzly, Skyline, and Redwood and through Palomares Canyon, then west across Fremont and back up on the Bay Trail. Coming in the near future.