Tierra Bella, Gilroy, CA was on April 17 this year. 100K climbing is reasonable. 100 mi a killer for us tandem folk
SLO Wildflower, SLO, CA, April 24 - climbing supposed to be reasonable (at least the 100K). Will find out next year.
Chico Velo Wildflower, Chico, CA, April 25 this year. one real climb on the 100K - definitely in your wheelhouse
Wine Country Century, Santa Rosa, CA, May, sold out - tandem friendly so you would be GTG. Did 70 miles of it last year and only 1 climb
Lighthouse Century, SLO, CA, June, sold out - almost no climbing in the coastal 100K and 100mi. beautiful ride
Marin, San Rafael, CA, August - 100K was doable on the tandem so np on a single. We'll do the 100 mi this year
Foxy's, Davis, CA, October - not much climbing on a single
Condor Classic, Hollister, CA, October - nothing we can't do on our tandem. np for singles. Can be windy on the way back from the Pinnacles
Cheese and Wine Century, Riverbank, CA (Modesto), October - not much climbing
Giro d' Vino, Lodi, CA, November - 100K almost no climbing, 100 mi a bit. Probably similar to the Delta Century
I'm sure there are others of course