EsoxLucius

I'm looking to get a lightweight tube to carry and was wondering if a 700 x 23-25 C tube can be used in a 700 x 28 C tire. Sheldon Brown/Harris Cyclery says, "Since tubes are stretchy, they do not need to exactly match the size of the tire." It would be for temporary duty to limp back after a flat. Thanks for your help.

CACycling

Running that combo on my commuter right now. Accidentally picked up the wrong tubes when I replaced the tires.

ScottNotBombs

It'll be fine. I've used tubes that were off by a lot more in a pinch.

cmill189

I've been using 18-23c tubes in 28's for a year without issue. It started off as an experiment that has worked out well; I carry one extra tube in the seatbag I use on multiple bikes.

jeepr

Ever inflate a tube out of the tire? It will expand to fill the available space. Much like all the junk in my garage has expanded.

FastJake

It'll also explode if it doesn't have a tire around it, if you go too far.

That tube in that tire will be fine. They're pretty flexible.

illwafer

completely acceptable. if i ever go on long rides i bring a smaller tube since it is smaller and less to carry.

EsoxLucius

That's what I was thinking. Thanks everyone!

chandltp

I don't know if this is always the case, but when you put a smaller tube in a larger tire, does it lose air faster? I put a 700 X 28 in my 700 X 35 and it loses air faster than my other tire.

CACycling

When you use a smaller tube, it will be stretched further resulting in a thinner layer for the air to escape through.

FBinNY 

As the others have said, no problem at all with a standard butyl tube. it will be stretched thinner so air bleed off will be slightly faster, but not enough to be an issue - pump back up in 10 days vs 2 weeks so something like that.

But there are limits to the stretch to consider

1- if you're buying a premium light tube, it's already thin walled, so thinning from stretching into a fatter tire might create noticeably faster bleeding. That's might, not definitely will.

2- and more important, if you have a narrow rim with a deep center well this could be a serious issue. As tubes fill they first fill the tire, then the short section spanning between the beads expands down into the rim. With a narrow rim it'll cause hyper-stretching of the belly section of the tube, far beyond what the rest of the tube sees. Normally tubes handle this with no problem, but if it's already stretched near it's limit you could get splitting or tearing in the belly, especially near the valve.

If you search the forum you'll see that it isn't a rare problem.

So my advice is if you already have the tubes, or that's all that's available go ahead. But if you're buying a narrow tube as a spare just to save a few grams, (and have narrow rims) you could be in for a rough time. After all this is your spare and if that fails what's Plan B?.

In summary, while one size does sort of fit all, there's a good reason that they're marked with a fairly narrow fit range.