That's my buddy Pete on his Klein with a 39x27 low switchbacking up. You name it, I've used it up this hill and I still have to tack near the end, 34x27, 39x25, 30x26, even for kicks a 28x29. The wrong side of the road has plenty of dirt and Eucalyptus leaves to lose traction on as well.

This is not quite the bottom. I always include this block on hilly San Francisco rides so people have something fond to remember.