I have been riding a trek hybrid thing that was given to me, it's not great on muddy gravel trails I frequent so today I went and checked out the local bike shops. I was looking for a used 26" rigid MTB. I ended up with a mid '90's Gary Fisher on 650B's, everything on it is new except the frame and fork. It has a lot nicer ride than the hybrid with it's much fatter tires, I'm super happy with it. I thought it would be slower than my old hybrid due to added rolling resistance of the bigger tires but was surprised the opposite seems to be true.
Two questions:
Is 650b the same as 27.5?
I lowered the tire pressure while out on the trail until it started to look slightly low with me on it(I'm 240lb). When I got home I measured the pressure and was surprised to see only 25psi. The bike felt good at this pressure, am I going to hurt anything keeping it that low?