Undersized road bike inner tube = more flats?

Here's the deal.

As you know, tubes are simply bladders that expand to whatever they are inside. As they expand the wall of the tube gets progressively thinner (think of making a pizza dough).

Depending on the original thickness of the uninflated tube you MIGHT be stretching it to the point of failure BUT a difference of 2mm makes virtually no difference... if the tube thickness is 1mm when uninflated (assuming that its "small tolerance" keeps it that way), an additional 2mm inflation will stretch the tube and reduce it's thickness by 0.15mm. That is less than 0.006" (six thousandths of an inch), or just about the average thickness of a human hair.

You noted that there was indeed penetrations through the tire which caused the flats. This means that the tubes had nothing to do with your problem

I have 700c X 25 Gatorskins on one of my cycles, and originally I used 700c X 18 - 25 tubes. With this set up I was constantly getting pinch flats. I'm quite heavy (OK, too heavy) and whenever the tyre pressures dropped below 100 psi I'd end up with a puncture.

I changed the tubes for some 700c X 25-25, and since fitting them, some 12 months ago, I haven't had a single pinch flat puncture.

I think it's because the narrower tubes have to stretch to fit the tyre, and this makes the walls of the tubes thinner, which in turn reduces their puncture resistance.

The first link shows the tubes I use, which have a 42mm stem, and the second link shows a similar tube with a 60 mm stem, so suitable tubes are available. If your local shop can't get them, you could order them over the internet. The company with this web site will ship to almost any country. There is a tab in the top right hand corner that allows you to switch to your local currency.

I will add that it's very unusual to get punctures with Gatorskins, in over 2,000 miles I've had two punctures due to glass, and one off those went through the sidewall.

You're getting punctures, so the problem is really with stuff getting through your tires. Gatorskins have a rep for being pretty resistant, but no tire is immune to having sharp stuff penetrate. Even the GS only has a puncture strip down the middle of the tread; it doesn't cover the whole carcass. So, point one is to stop riding in crap. I never ride in the shoulder and that's why.

Point #2, tubes come in different widths, but also in different, well, weights. you can get thin racing tubes or thicker touring tubes. The racing tubes are more fragile but will be faster. The touring tubes will be heavier, nominally more resistant to things like pinches, but be slower. It sounds like you want the heavier tube.

Point #3, if you live in goat head country, you WILL get flats no matter what tire/tube combination you use. Deal with it.

Tubes are rated for a range of sizes. I bought 700 X 18-26c. Check where the hole lines up with the tire or rim. I always find the cause still in the tire. You can always add Mr Tuffy tire liners. Also make sure the tires are properly inflated.

nothing is unusual for flats

as far as stem, try pushing it out with your thumb through the 'flat' tire

if it is too short

no using a 2mm 'narrower' tube won;t do anything

wle

Continental Gatorskins 700x25