Going up this truly massive hill around these parts (known as "the wall" by certain folks) I tend to drop to about 25 gear inches on the road bicycle and think about every hardcore song I've ever heard. That usually will get me close to the top, but then I loose it and I have to drop down as far as I can get. So maybe something less than that? It's about a 17 percent grade at the toughest spots.

edited to include the grade of the hill.