So it's okay to use a smaller tube in a 28mm tire?
 

One person suggested that our 28-32mm tubes were huge for a 28mm road tire. I know that our 28mm Panaracer Ribmo tires really are a true 28mm and are also just a bit taller than the other 28s we used prior to these. Having said that would you have any qualms about the 19-26mm tube being used in these 28mm tires (on a tandem, of course)? Just looking for more opinions or experiences from other people that will say "yea" or "nay" to this idea.

I like the Specialized 20-28mm tubes. You can usually keep them inflated a bit during install, but they don't seem too tiny. And 20-28mm 60mm valve covers every road bike I have. They pack fairly small for your bag too.

Used tubes for a 23mm tubes in 28mm tires for over 10,000 miles with no problem. They loose air in a fewer number of days but most people seem to pump up their tires every ride anyway. Hey it saved 20 grams a tube that is 60 grams!

I would suspect that "over inflating" to 28mm the tube would stretch it and cause it to loose air faster and perhaps make it prone to flatting, however waynesulak seems to have really good luck, better than I've had with some of my tires/tubes!

I've been using the smaller tubes for several years and many thousand miles with no problems.

Not a problem, even up to 32mm.

I too have always used one size smaller tubes for several years as a matter of practice and I have never had a problem.

No problem with 20-23, etc, in a 25mm tire, but then were any of our flats caused by a smaller cheap tube failure? The smaller tubes stash so much easier, and the punctured tube fits easier in a rear pocket. I stopped putting the punctured tubes back into the saddle bag because I would forget to change it out when I got home.

I've used both smaller and larger tubes in our 32mm tires with no obvious problems, although who's to say if a flat could have been prevented by a "wrong" size tube. I always buy the correct size tube if they are available, but I'm not concerned if I have to go one size up or down.

+1

The smaller tubes will be a fraction lighter and will be a bit more supple in my experience.

I currently have a 19-26mm tube in the 37mm tire on my touring bike and wouldn't have any qualms about doing the same on our tandem. As others have said, it just stretches the tube a bit more so the rubber is thinner and needs pumping a bit more often than a wider tube.

The interior diameter difference in a tire is minisucle, a total of 3mm. Compare that to the capacity of your inner tube - go grab a spare and pump it up to 40-50psi, then watch how large it will grow. Within a minute it will likely double the inner diameter of a 28mm tire.

Safety warning: wear eye shields, face shields, ear protection, do not stand near the top of stairs, do not inflate while driving, riding or having sex.

Yes!
Been doing that for over 40 years . . .

You just have to be in the ballpark for tubes.

From what I have been told, it take a LOT of pump strokes to get a tube to the point where it will explode. In the region of 250, IIRC (based on a competition for people to guess how many pump strokes it would take).

Indeed, the thickness of the tube when inflating a tyre of larger size won't change much at all.

And given the choice, I prefer to go one size smaller rather than one size larger. Tubes that are too big are too easily pinched under the tire bead.

There is also quite a lot of variation in manufacturer's labeling. A tube that one manufacturer might label 23-28, another one might label the same size as 25-32. Tubes that are too big cause problems with mounting the tire; tubes that are too small rarely cause a problem. I've often used tubes rated as a smaller size, and in a pinch I've even used tubes for 26" x 1.25 (559x32mm) in 700c tires (622x32) - that requires a bit more stretching, but is still not very difficult.

I'd not heard of the tactic of deliberately using tubes that are one size smaller to save weight - I'll have to consider that.

My over-simplified analysis:

Using a normal thickness tube in a tire larger than it is specified for essentially turns it into a lightweight tube bying reducing the inflated wall thickness slightly.

We run lightweight tubes in our singles, but I like having a little extra margin for the tandem, so I make a point to match the manufacturer's range closely to our tire size and only use regular weight tubes on the big bike.

YMMV.

Not just to save weight. The thinner tube is also more supple, giving a better ride.

Ok, so tonight we had a chance to do this. I just changed the tires on my tandem to 700c x 28 from 23s. Also had a cassette hub failure which caused me to put a rear wheel on that had a 700 x 35 tire. Grabbed a 28 - 35 tube "just in case." Had the 28 on the front.

At the start of the ride tonight we had a blowout on the front wheel (28). Grabbed the tube from the tool bag and put it in. Inflated to 100 psi and headed out. After about 10 mi and NOT on the 30+ mph hill descent, got another flat on the same tire. Pulled the tube and realized it was an 18-23 tube that I had in the tool bag from before I had changed the tires to 28. The tube failed on one of the seams. No damage to the tire, so it was just stress failure from being over inflated in the 28 mm tire.

So my advice is, don't do it unless an absolute emergency, and then don't inflate much. Just enough to allow you to ride directly to get the problem corrected properly.

OK, I know I'm reviving an old threat here but I've been reading through the old threads learning about tandems and I came across this.

My experience is that sure you can use smaller tubes in larger tires as many have already noted. HOWEVER....if you are old school and like to patch your tubes instead of just replacing them you will find that your patches will have a much higher failure rate if you are not using the correct size tube.

Tubes are very stretchy and small tubes can fill the space of a large tire. However patches generally do not stretch much at all. When you patch a tube you are affixing the patch to the tube when it is in its relaxed (un-stretched) state. When you then put the patched tube in a larger size tire and inflate the tube will stretch to fill the tire but the patch will not which will put a LOT of sheer force on the patch adhesive. If you are obsessive about how you apply patches you may get away with it just fine. But if you are using the new adhesive-less patches or are just sloppy about applying patches you are asking for failure.

Bottom line? If you carry around new replacement tubes then there's probably no problem using undersized tubes. However if you carry a patch kit and like to patch your tubes then you are increasing your chance of failure if you don't use the correct size tube.