Flat Analysis

[quixoticgeek]

Was scrolling through the photos on my phone when I noticed a photo I took in September of a hole in one of the tubes from the rear wheel of my bike. About a month ago I had another flat, and took a photo of the hole, as it was on a seem and I was a bit surprised by it. But now, looking at the two pictures side by side, I can't help but think both holes are in exactly the same place on the tube (relative to the valve).




If they are in the same place, which is on the inside, by the rim, rather than the outer tyre side. Could this be a defect in the rim tape? Bit of grid embedded in the rim tape? I haven't taken the current tube/tyre off the wheel yet, gonna do that in day light, but am wondering what I should be looking out for. Something sharp enough to go through a tyre like this should be feelable with a finger right? Should I replace the rim tape as a precaution?

J

[hubner]

Are they 2 different tubes?

It doesn't look like a cut or a hole caused by a sharp object, it's more like a split, maybe it's a manufacturing fault?

[Jurek]

Are they Spesh tubes?
I had a number of Spesh tubes fail at the point where the mould parted, and there was some flash left on the tube.

[Pickled Onion]

It looks very like a manufacturing fault. Don't try and fix it, it will continue to split.

Last time I was on tour, I took a Several of brand new continental tubes, all bought at the same time. They all had that fault, on repairing the split would gradually lengthen under the patch and fail again. With that and the wires shed from the ubiquitous bald tyres on the local motor vehicles I was close to being stranded a very long way from any civilised bike shop.

[Brucey]

I agree it looks like it could be a manufacturing fault. However it may not be; such failures are more likely to manifest as a puncture if

a) the tube is stretched a lot when it is fitted and/or
b) the tyre pressure is fairly low and/or
c) the tyre is a slack fit on the rim

The second picture looks to me like the tyre has been chafing against the tube; those diagonal marks are quite distinctive; this only happens if you run low pressures IME.  If the tyre bead is not seated perfectly on the rim (i.e. the tyre is a slack fit or is not uniformly seated) then there is a small gap between the tyre bead and the rim. The tube (even if not actually pinched/trapped, which will certainly cause the tube to fail thusly) will tend to bulge into this gap, and (especially in combination with any movement due to low pressures) may manifest itself as a split in the tube. If the (plastic)  rim tape is not full width and the edge is in contact with the tube, you will see exactly the same thing too.

So some things to look out for

1) that you are not using a tube that is too narrow; tube manufacturers are notoriously optimistic about this (I'd describe some Schwalbe recommendations as 'ludicrous' BTW) and IME if you run low pressures in a rear wheel, it is best to stick to tubes that are sized so that your tyre is near the smaller end of the range of widths that the tube is meant to be OK with.

2) that the rim tape is OK.  Cloth rim tapes are kinder to tubes, but a touch thicker than some plastic ones.  It is (provided it doesn't interfere with tyre fitting too badly) a good idea to use a full-width cloth rim tape in some rims.

3) that the tyre pressure is high enough that the tube isn't moving and chafing (ie so you don't see those diagonal marks)

4) that the tube isn't pinched and isn't finding its way into a gap beneath the tyre bead edge.

HTH

cheers