hrdknox1

I mistakenly purchased 700x25-32 inner tubes. I've always used 700x18-25 inner tubes. My tire is 700x25. Am I better off using the smaller, or larger inner tube?

cxwrench

The smaller tube will be much easier to install.

hrdknox1

Good point....and mounting the tires on one set of rims I have is tight to begin with.

Iride01 

If the 700 x 25 - 32 fits without wrinkling in the tire then it might be less prone to flatting. Or if it does get punctured it'll have more of a chance to being a slow leak instead of a balloon being popped.

It might be somewhat more difficult to install on a narrow rim without inadvertently damaging it with a lever or pinching as you roll the tire bead over the rim, but I now tend to favor using the larger width range that is for my tire size.

And no, just because in the first paragraph I likened the small range to a balloon being popped, does that mean that I feel it does that often and every time.

zacster

I started using 25-32 tubes on my 700x28 tire but it would also fit easily in a 25. If that's what you have, use it. I bought 5 of them at once because that was the only way to get them a year ago when everything bike related was in short supply and I figure that I seem to go through tubes on a regular basis. Since I bought them though I've only had one issue and that was when I broke the presta core.

ThermionicScott 

The tube is designed to work in a 700x25C tire, so the rest is up to you.

As always, putting a little bit of air in the tube before installing will help keep it from getting caught under the tire bead. Just enough so it starts to take a circular shape, but not so much that it starts to puff up. If you're unafraid of germs, what you can put in with your mouth will do it.

3alarmer 

...I think the website where I buy Conti tubes in bulk numbers recently started recommending the larger 25x32 tubes in 25's as under less elastic stretch, thus less prone to flatting than an 18x25. I'm uncertain what they are basing this on, other than some thought process. The fatter tubes are a tiny bit heavier, so add a small bit to the rotating weight. I pretty much use them interchangeably, and try not to worry too much about it. I have plenty of other stuff to worry about.

Bonzo Banana

Personally I would go with the larger inner tube because it should be thicker when used with the smaller tyre and therefore slightly more resistant to punctures. However it doesn't end there I pretty much buy my inner tubes when I see them cheap so price would dictate what I would buy to a greater degree. However if they were the same price for either size I would go with the larger inner tube.

What I always find confusing is inner tubes that give one size and little other information. I.e. 26x2.125". Is that up to 2.125" or nominal at 2.125" and capable of a bit either way or maybe its the minimum size tyre. When I actually look at the inner tube it felt like 2.125" was the absolute maximum but I'm sure I've had other inner tubes where that didn't apply. Then you get inner tubes which have a greater tyre range than other similar inner tubes. Why can this inner tube do 1.75-2.5" when other similar inner tubes can only do 1.95-2.125". Is that an indication that the rubber is thinner so can stretch more? Just making the point there are quite a few variables in play.

ThermionicScott 

Since tubes don't know what tire they're going into and will expand in all directions until failure, I'd imagine the labelling just indicates what the manufacturer is comfortable with. Someone in the legal or warranty department doesn't want the hassle of people sticking a 700x18C tube into a 3" 29er tire and having failures, so they draw the line somewhere.

My preference is for tubes that are manufactured to have thin walls, but then to use a size that doesn't require them to stretch much. That way, I get the benefits of lighter tubes, but without the concern that an extra-thin spot has developed anywhere.

70sSanO

I’ve started going to 25-32 tubes in 700x25 tires. It is tougher to fit in the tire, but I did it for less expansion/thinning of the tube wall. I also have 700x28 tires so it is easier to buy and stock one size tube.

John