rpenmanparker 

OP, not exactly. You could be right, but so is HTupoley. Combining a tube with the smallest tire for which it is speced will make mounting extremely difficult. There will be so much excess, you will have a devil of a time cramming all the tube into the tire. And when you are done, some of the tube may be folded up on itself inside the tire. Also tubes for bigger tires are generally heavier with thicker walls than tubes for smaller tires. This is because larger tires are generally used for rougher terrain and weight is not usually an issue with larger tires. After all theybare not intended for lightweight road racing bikes. If you mount your tires properly and ride the right way, you shouldn't have much of a puncture problem even with light tubes. I strongly recommend you use the SMALLEST tube speced for your tires, not the largest.