I rode out to Redwood Park and then over the East trail to Pinehurst. Then down and up to Bort Meadow and on to the Stone Bridge. There I almost crashed while hitting a nearly invisible ridge along the trail. I had almost crashed there a few days ago too, when the shock caused me to lose contact with the handlebars. Today was a bit different. I was holding on well this time but still "forgot" about the obstacle and went so fast I was airborne instead.
I turned around at the bridge and went back to inspect the obstacle. It is a sharp narrow steep ridge about 4-5 inches tall running across the trail. I have no idea why it suddenly appeared there and I am sure it wasn't there before. Maybe the erosion exposed a rock layer that was previously covered up?
The location adds to the problem. It is at the end of an open and sunny downhill stretch in an area that is narrow and wooded. You go from bright sun to a dark spot so you really can't see very well there -at least for a while- and when you hit it at high speed like I did, you go flying up in the air.
I came back over McDonald to Skyline and then through the park (West Trail) to Skyline again. The climb was in the sun and there was no breeze there so I quickly got quite hot. Near Grizzly however, I was met with a vicious cold wind and in some spots it was hard to move, so strong were the gusts. By then I had been sweating a bit and when the cold wind hit me it was quite chilly. I was very grateful for my thermal vest.
I would guess about 25-27 miles.