polymorphself 

I've got some 700x32 tires and two different sets of tubes: One set is 700x25, the other is 27x1 1/8 (maybe 1/4, not sure at the moment). Will either of these work in the 700x32 tires?

nlerner

Yes, both should work fine (assuming their valves, Presta or Schrader, match the rim drilling).

Kuromori

Inflate a tube outside a tire and you'll find it can expand quite a bit. The danger with using a tube for a narrower tire is that some poorly made tubes have thin spots, and they tend to stretch even thinner there when inflated, leading to increased risk of flatting. The danger of using a tube for a larger diameter wheel is that the tube will fold over on itself and wrinkle to fit on a smaller diameter wheel and cause a pinch flat. Most modern 700c tubes say they also have 27" compatibility because the difference in circumference is only ~1% and rubber can stretch more than that. 26" tubes can also generally be used in 650B tires because 650B is only ~4% bigger.

Both of these problems are unlikely with the tube/tire sizes given, but neither can be completely ruled out. 27" has about an inch of extra circumference, more than enough for the tube to wrinkle and fold over itself, but is a non issue if the tube is just slightly undersized. Jumping a couple sizes from 25mm to 32mm is usually not a problem, but it can be somewhat of a problem with particularly cheaply made tubes which will show bulging when inflated out of a tire.

CliffordK

I've used 700c tubes in 20" wheels. Just carefully fold the tube as I'm laying it in.

It may not be a perfect solution, but it can get a person back on the road. I'm not sure if it caused tube damage over the course of hundreds or thousands of miles.

katsup

Using a 700x25 tube in a 700x32 tire may blow the tube, at least that was my experience using a tube that much smaller. Just be prepared to cause an unpatchable hole in that tube if that happens (and use it in the back tire).

I believe tubes sold as 27x1 1/8-1 1/4 are also marked as 700x28-32 so that may be the correct size.

polymorphself 

Got it. I'll try those. Thanks.

Choke 

I've been using tubes marked 700x18/25 (Michelin A1s to be exact) in 32mm and 35mm tires for years with no problems.

DMC707

Ive used 700c road bike tubes in 26" mountain bike tires before in a pinch.

Got the job done - don't recall any dramatic side effects

dddd

I see a several issues here.

Firstly, tubes labeled as up to 25c can have different actual widths, from about 22mm to about 25mm (measured folded, not immediately after extended use in a tire).
Tube quality (the rubber itself and it's consistency of thickness), varies between brands, and some are much less good than others.

The area near the valve stem will have only about half of the tube's minor circumference doing all of the stretching to fill the much-bigger tire. This is the area where an inflated tube looks like a sausage necked down near the valve stem. This area is known to fail spontaneously when standard "road" tubes are used in 27x1-1/4" tires.

Lastly, the rate of deflation when punctured by a small thorn will be very much faster than normal when a small tube has been stretched to fit a bigger tire.
Conversely, a tube with a folded flat width slightly greater than the tire's actual inflated width may allow you to complete your ride perhaps without even noticing any air loss has occurred. I've noticed this when using some wide hybrid tubes in my 27x1-14" tires.

An adequate standard road tube these days is the one from Specialized marked 20-28mm. While no longer made with short valve stems, these have a folded width of 26mm and seem to hold up well even in narrow CX tires and in most normal (i.e. not Michelin or Pasela) 27x1-1/4" tires. These weigh about 108g.

There were better tubes sold way back in the 80's. Made in Japan, many had thinner walls, so could measure 28mm wide folded and still weigh only ~75 grams, something that I can't find any more (except pulled out of used bike's tires).

miamijim

Run the biggest size tube you can. Undersized tubes, like an 18c in a 32c, have to stretch a lot to fill the tire. They can get very thin and stiff thus more susceptible to punctures. Kind of like over inflating a balloon, to much and ball point pen will easily puncture it, but if its not stretched that same pen may deform the balloon before it pops.

dddd

On that note, I have more than once borrowed a standard road tube while out riding, to put in my 27x1-1/4" tire, and it always got me home.

But I admit to doing the same thing in another rider's bike, only to find out that it failed shortly after. And I've bought used bikes where a narrow tube was found ruptured near the valve stem due to same cause.

And, while some CX racers used standard road tubes for their lighter weight, these were for short races, in an era when clincher tubed CX tires tended to be narrow, mounted on narrow rims.

Narrow tubes can show other failures when used with narrow rims, since the tube first inflates firmly inside of the tire before then having to expand further to full the rim cavity between the closely-spaced beads. The already-stretched tube must then be dragged "around the corner" down into the rim cavity while already pinned by air pressure inside of the tire casing, which I have seen cause ruptures on the rim side of the tube (especially adjacent to the valve stem reinforcement, where the rubber "pad" resists being bent sharply enough to be forced down into the rim cavity). The tell-tale stretch marks are so often found there, even on tubes that have not yet failed.

ThermionicScott 

@dddd, have you considered Schwalbe tubes? They make some 700C tubes that are lightweight, have 40mm valves, and have pretty consistent wall thicknesses.

700C x 18-26 mm Superlight (SV20), 65 g
700C x 28-45 mm Superlight (SV18), 107 g

Only downside is that the extra light ones are not cheap.

Kuromori

My experience is Schwalbe weights aren't accurate at all and their tires come in measurably higher than advertised. Schwalbe CS insists it's unreasonable to expect them to actually adhere to their published +/-8% tolerances, and insists that further allowance should be made on top of their stated 8% variance, because they can't actually be expected to weigh their products or manufacture them so they come within the original tolerances. Schwalbe and advertised weights are a complete farce.

It's not just restricted to one bad batch either and they keep advertising the wrong weights year after year, across product lines, and it's more like -1%/+15%. The weight data on sites like bicyclerollingresistance show this too. You're lucky if it comes in at advertised, and it's not at all unusual for it to be more than the maximum advertised +8% heavier.

ThermionicScott 

My Schwalbe tubes have all weighed below spec, go figure.

Kuromori

I guess you got lucky or they changed things. I checked weight weenies tubes listings just to see if their weight problems are just for tires, but the reported tube weights there also tend to skew towards overweight.