Stuffed inner tube

[Nettled Shin]

I had an inner tube fail where the rubber stem is moulded up the brass Schrader valve stem. Air was escaping at the interface. I'd never seen this happen before, and it annoyed me as it seemed more or less irreparable. I've seen on here before people complain about tubes failing at the stem, but I hadn't thought this was what they meant.
To teach it a lesson, I cut a hole in in, and tried doing this to it.
It does work in that you get another torus, but it isn't anywhere as exciting as in the animation.

[cyclingvirtual]

you should have painted red lines on it first then

[Brucey]

I had an inner tube fail where the rubber stem is moulded up the brass Schrader valve stem.....it annoyed me as it seemed more or less irreparable.

years ago many tubes came with 'bolt through' valve stems. Being a tightwad, I used to salvage these and use them in failed tubes of the sort you have just had.

Nice animation BTW

cheers

[PT1029]

As someone who repairs bikes - usually with underinflated tubes - tubes often fail from the (underinflated) tyre slipping round the rim and dragging the innertube with it (except where the valve is fixed of course). One side of the valve the tube will be stretched tight, the other side all folded up on itself. This drags the valve away from its 90 deg position, causing failure.
If you keep your tyres properly hard, the same result can be achieved with sharp braking after a puncture. Possibly you had a puncture (not at the valve stem), but once soft the valve stem gave out. Only hypothseis, as you can't reinflate the tube to check for a puncture away from the valve!

[Nettled Shin]

Possibly you had a puncture (not at the valve stem), but once soft the valve stem gave out. Only hypothseis, as you can't reinflate the tube to check for a puncture away from the valve!

I don't think so. The tyre had never deflated from a puncture in the two years it had been fitted, so the tube or valve had never seen abuse. The air was coming out from a pinprick sized gap at the top of the stem, where the butyl rubber ended. It only came out above 20PSI or so. I suppose, fundamentally, rubber doesn't want to stick to metal?

[ANTONISH]

Some years ago I had a spate of problems with valves coming away from the tube. In one case it happened to a new tube. At the time I was using Vittoria but it seemed commonplace - the valve seemed to be fitted into the tube with no reinforcement. I now use Continental tubes but I think generally manufacturers have improved the valve seating. OTOH the extra reinforcement means taking care not to trap the valve seat under the tyre bead - I had to stop and help someone at the weekend as for some reason her tyre had developed a lump.

[CJ]

I think the tube is parted from the valve by the sharp edge of the valve hole in modern double-wall rims, which leave no room for the cushy rubber rim tapes in the simple rims of old. Since I started putting rubber washers onto valves (cut out of failed inner tubes with a leather-punched hole half the size of the valve) I've not had one thus treated fail like this - only valves in wheels that I've not got to yet.

[Nettled Shin]

Here's where mine was leaking.

LeakyValve.jpg (5.18 KiB) Viewed 940 times

[Brucey]

now that is unusual....

Normally the rubber finishes lower down and that is where the split is....

cheers

[ANTONISH]

I think the tube is parted from the valve by the sharp edge of the valve hole in modern double-wall rims, which leave no room for the cushy rubber rim tapes in the simple rims of old. Since I started putting rubber washers onto valves (cut out of failed inner tubes with a leather-punched hole half the size of the valve) I've not had one thus treated fail like this - only valves in wheels that I've not got to yet.

I dealt with this in a similar way when I was having this problem a few years ago.
I resorted to punching a hole in a puncture repair patch and reinforcing the valve area before using the tube for the first time. I've not needed to do this for some years now. I've always used cloth rim tape and usually Mavic rims. Occasionally I find the valve hole on a new rim needs to be deburred- but I think the valve seat failures I experienced in the past were mainly due to poor manufacture.