Originally Posted by
cyccommute
Yes, there is a limit to how much the rubber will stretch but going from a 23mm tire to a 32mm tire isn't even coming close to the limits. People seem to get hung up on just how big an millimeter is...possibly be cause it's a whole number instead of a fraction. The difference is 9mm. To put it into something concrete, that's the thickness of 4 nickels and 1 dime. Or it's a bit less than 3/8". Not much at all.
A 32mm tube in a 35 mm tire isn't even enough to worry about.
Yup, id use a 23 in a 32 if necessary. I didnt say that such a size difference is coming to the tube's limits.
Yup, i agree a 32 in a 35 isnt anything to worry about which is why i posted that itll work.
I said a 23 in a 40 is dumb because there is no need for it. Want a smaller tube in a 40?...use a 32. Tubes come in multiple sizes for a reason and a small difference like 32 in a 35 which is the OPs question is nothing to think twice about. But there is a reason why tubes come in different sizes.
I use 35-43s for my 40mm tires so clearly there is a safe and acceptable variance in tire size for tubes.
Perhaps 23 in a 40 isnt a large enough difference, but i would think it is and wouldnt use a 23 unless i didnt have a choice. So say 23 in a 2" 29er. Or 23 in an even wider tire. The point was that small differences are ok but there is a limit. Thats all.