Originally Posted by
tjspiel
Yes, but as it expands the walls get thinner making it easier to puncture. A few mm isn't going to make much of a difference but I wouldn't a skinny tube designed for 23 to 25 mm tires inside a 45 mm tire for much longer than it took to get home.
My touring bike has 25mm tubes in 35mm tires, and has given me no trouble. I also have 1.5 inch tubes in 2.35 inch tires on my mountain bike, without a whisper of complaint. The standard road tubes are easier to find and pack much smaller.