I have a 2005 Giant Cypress with original tires that are 700x40C.

Every time I go looking for a tube all the tubes at several LBS's & sporting good stores are either 700x35C or 700x38C. The bike stores always tell me don't worry these tubes will fit. Well my attitude is I don't want to fit, I want them to be the correct size.

I know I can order the correct size online, but I hate to have to order everything online.

So my questions are: Is this such an odd size that no one regularly stocks these tubes (even the local Giant dealer!)? Can I use the smaller tubes without any problems? If so, why?

Thanks!

Really, either one will work. If it was me, I'd pick the larger of the two.

You can use either one, because they are very stretchy. The larger one will stretch "thicker". It will be fine, honest.

If you're that obsessive, order online.

I wouldn't worry about it. There's enough variation is the actual width of tires (many run narrower/wider than their advertised size) that tubes have to fit a wider range of tires than you think. Stuffing a bigger tube into a smaller tire can be difficult though.

The bike shop is correct that they'll work fine. One of my bikes has 23mm tires and the other has 40mm tires. The same tubes work fine in both. Tubes stretch just like balloons so their width when in use is determined entirely by the tire that surrounds them.

I thought most tubes were marked with a range anyway, such as "700x35-40" or whatever. But what's offered is strange. I have three bikes with 700c rims that, going by the ratings, would each take a different tube! For example, I have a 700x25 and 700x28. The tubes I've seen are either for "23-25" or "28-32", but nobody seems to make a "25-28".

Anyway, I'm managing to use one tube size for the 700x25 and 28 bikes and a larger size for the 700x38 hybrid.

I don't have the box in front of me, but the last time I bought a Giant brand tube it was marked for a range of tire sizes. There is no need to make separate pacaking for every tube size, all you really need is a few different options.

The bike shop is right, just buy the tubes used for 35+ and you should be just fine.

Last flat I had, stuck a 700 x 32 tube in a 23.. But I have always looked for the right size also.