Inner tube failure at valve.

[sirmy]

This is probably something without an answer but I've had three inner tubes split at the valve on the same wheel within less than 300 miles.

I've tried ensuring the washer is screwed up to the rim to stop the valve moving when inflating, running very fine wet and dry around the valve hole to remove any defects, I even tried cutting a length of old innertube, putting a slit in it and passing it over the valve to ensure it didn't come into contact with the rim or the rim tape. Didn't work. I've now changed the rim tape, although I'm not sure if that will make a difference

Has anyone got any suggestions as I'm losing confidence in using this wheel and buying new tubes for it feel slike throwing good money after bad.

[Brucey]

I would suggest that it is very likely that the hole in the inner wall of the rim is too large and thus the valve body is not well supported. If you look at the valve carefully you will likely see that there is a small ridge that will engage with a hole of the exact right size. A rim tape alone won't work and tightening the nut on the outside will just make things worse! In all fairness there are occasional bad batches of inner tubes too, so it could be that.

There are various ways to fix this;

- fit a metal washer of the correct size
- fit a rim converter insert
- fit a valve nut on the valve stem, inside the rim

and so on. The problem always seems worse with high pressure tyres BTW.

cheers

[simonpbaldwin]

I've had this problem in the past. I have also recently had two tyres suddenly, several minutes after stopping for a drink start hissing and deflate. I came to the conclusion that I was running the nut too far down the valve body. So I now wind it back half a turn, so that it is loose. I'll see how it goes.

I think of the nut as assisting for attaching the pump. When the tyre is inflated it doesn't need locking in position. Indeed the movement as you cycle over bumps and variations in temperature maybe causing stress to the valve bond by running the nut tight. Some tube manufacturers do away with it altogether.

[MLJ]

Cut a washer from the damaged tube, around the old valve. Add this to the new tube before fitting. The extra cushioning will help protect the valve seating against the rim hole.

[kwackers]

I've had this when the tyre pressure has been too low and I've been riding aggressively. The tyre slips on the rim and pulls the tube tearing it at the join with the valve.

[sirmy]

Could be low pressure, I use Schwalbe marathons which I run at the lower end of the recommended pressure

[Brucey]

if the tyre and tube are creeping round it will certainly pull the valve out. You will know this is happening because the valve will want to sit at a jaunty angle, not the one it sat at when you installed it.

NB if you run recently manufactured Marathons at low pressure, the tyres themselves can suffer bead failure. They work best if you keep them fairly hard IME, more like a 10% drop than a 15% drop, as it were.

cheers

[cycleruk]

I know someone who puts the knurled nut on the valve before fitting the tube.
ie. Inside the rim.
I have recently had a couple of valve failures at the tube ( Continentals). The valve body just fits in the tube with apparently no reinforcing as I'm sure there used to be.