Innertube valve puncture-problem

Any thoughts on this please.

On the same wheel I have in two weeks had the rubber split next to the valve stem causing a puncture.

The stem-hole does not seem to have any sharp edges, I have kept the tube at the same pressure (for the last two years - the same wheel, same pressure).

The valve is in at 90 degrees. I do not even have a wild theory about why this is happening. Any thoughts out there please?

Same brand of tube? Michelin?

Try a different brand and see if it happens again.

Thanks - but the same thing happened twice with two different makes, I cannot remember which makes now, but I am sure they were different ...

put some rim tape over the hole, then stab a hole through the rim tape, and try again,

just because you cant see a sharp bit, doesn't mean that it's not there

Thanks, good idea, I will try it.

Were you using locknuts on the valve, and if so, did you get a bit over-zealous tightening them?

Or a bit heavy handed pumping them up? that will rip them out.

Examine very carefully for sharp edges or bits first.

When putting your tyre on, start with the part near the valve (ensuring that it is straight) go around the wheel pushing the tyre onto the rim.

Put locknut on after the tube is partially inflated.

that should keep it straight and stop it tearing etc. then you can look more carefully at other causes .

other things to consider,
tyre moving round the rim under braking and moving the inner tube, due to worn rims, worn tyres, too low pressures or just plain bad luck

punctures near the valve are usually caused by under infaltion or the valve not sitting square to the rim. 20c-25c /700 tyres need a min of 80psi i'd say to be good for goin.

has the valve hole been drilled out for a schraeder valve and you've put a presta tube in? this can sometimes mean the valve moves around and might dig in on the edges.

Dear all, thank you - very useful, I will do/bear all of this in mind and see how this new tube does now .......

Or a bit heavy handed pumping them up? that will rip them out.

+1, I ruined two good tubes last week with a stupid Crank Brothers mini pump, got too vigorous and snapped the valve stem off the tube, twice, Epic pumping Fail. Don't know why I didnt hurl the thing into the bushes long ago???? Result: new better pump, easier to use and no damaged valve stem.

Dredge

Same issue, for many punctures now.
Valve is nice and straight when I replace the tube, and remains so after being inflated.

After cycling it moves to this position, which is causing it to split where the valve joins the tube.
Rim and Tire are both 29er. Inner tube is a Schwalbe 19 (ive tried other brands)

Whats causing this movement? Underinflation?

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its underinflated so when you brake the tyre and tube slip on the rim.

thanks, i've upped the inflations and will see