I had this same kind of spider land on my leg while riding on labor day. It was huge and I was semi-freaked because I didn't know what kind of spider it was, and I was climbing and couldn't take my hand off the handle bars for about 30 seconds...to finally brush it off.

While I clearly know in hind sight that it wasn't poisonous (since I'm still alive) it was scary to see it come out of a tree, land on my leg, and see its size