so let me get this straight cause I'm in a similar boat... perhaps just the opposite of the original poster
I purchased some tubes (18-23 or 20-25... don't recall exactly... but on the smaller order) as I had been running 700-23's on my bike
Then I decided to try some Conti 28's for a tour I'm doing
so the tubes I have are SMALLER than the tire size.
Can I assume the tube will easily INCREASE to cover the difference?